A new erpetosuchid (Pseudosuchia, Archosauria) from the Middle–Late Triassic of Southern Brazil

A new erpetosuchid (Pseudosuchia, Archosauria) from the Middle–Late Triassic of Southern Brazil Abstract The evolution and diversification of Triassic pseudosuchian lineages has been the subject of much interest and revision in the last couple of decades, fuelled by new and important discoveries, which have allowed for better-sampled phylogenetic analysis. In the present contribution, we add to this by describing a new taxon, Pagosvenator candelariensis gen. et sp. nov., for the Middle–Late Triassic Dinodontosaurus Assemblage Zone of the Santa Maria Supersequence of southernmost Brazil. A comparative osteological analysis combined with a phylogenetic analysis supports its inclusion within the clade Erpetosuchidae and provides an insight into the phylogenetic relationship and evolutionary history of this clade, with two possibilities for the Erpetosuchidae relationship: as an early branch of pseudosuchians, being a sister group of Ornithosuchidae; or a closer relationship with the clade composed by Gracilisuchidae and Paracrodylomorpha with respect to Orntithosuchidae and Aetosauria. Additionally, the results presented and discussed here are of biostratigraphical importance, given that the taxon is from the Ladinian/Carnian age and would fill a temporal gap that exists within Erpetosuchidae between Parringtonia gracilis from the Anisian and Erpetosuchus from late the Carnian to Norian. Furthermore, it would be the first occurrence of a member of this clade in South America. Archosauria, Brazil, Erpetosuchidae, Pagosvenator, Santa Maria Supersequence, South America, Triassic INTRODUCTION Archosauria is a diverse clade composed of the crocodilians, birds and many extinct lineages (Gauthier, 1984; Gauthier & Padian, 1985; Benton & Clark, 1988; Sereno, 1991; Juul, 1994; Brusatte et al., 2010; Butler et al., 2011; Nesbitt, 2011; Ezcurra, 2016). Historically, aside from dinosaurs, there has been reduced enthusiasm over this clade and other non-archosaurian archosauriforms that also evolved in the Triassic Period; however, recent rekindled interested, sparked by new discoveries (e.g. Nesbitt et al., 2014; Ezcurra & Butler, 2015; Pinheiro et al., 2016; Stocker et al., 2016) along with revisions of previously described taxa, indicate a much richer diversity than was previously imagined (Brusatte et al., 2011). These discoveries have allowed for better-sampled matrixes and more robust cladistic analysis (Brusatte et al., 2010; Nesbitt, 2011; Butler et al., 2011; von Baczko, Desojo & Pol, 2014; Nesbitt et al., 2015; Ezcurra, 2016). Although consensus has been reached in some topologies, with historically clear monophyletic groups, such as Aetosauria (Brusatte et al., 2010; Nesbitt, 2011; Desojo et al., 2013;,Parker, 2016), others, such as the relationship of Phytosauria among archosauriforms (see discussion by Nesbitt, 2011; Ezcurra, 2016) and problematic taxa that are represented by mostly incomplete specimens display low support owing to data matrixes with ambiguous characters or a history of conflicting topologies (e.g. Gower, 2000; Brusatte et al., 2010; Nesbitt, 2011; Nesbitt & Butler, 2012; Nesbitt et al., 2013; Ezcurra, 2016). Unfortunately, even with these new insights, there are still many taxa represented by only a few or mostly incomplete specimens, and a large number of ghost lineages still haunt our view of the Triassic biotas. This is, of course, the nature of the fossil record, so there is a need for new discoveries to advance our understanding and to achieve better-supported phylogenetic analyses (Fig. 1). Figure 1. View largeDownload slide Distinct proposals of phylogenetic relationships within archosauriforms and archosaurs. A, Butler et al., (2014) based on a modified matrix of Nesbitt (2011). B, Ezcurra (2016). C, modified cladogram of Nesbitt & Butler, 2012 with the red lines and asterisks indicating the possible phylogenetic positions of Erpetosuchidae. Abbreviations: Arcf, Archosauriforms; Arch, Archosauria; Ps, Pseudosuchia. Figure 1. View largeDownload slide Distinct proposals of phylogenetic relationships within archosauriforms and archosaurs. A, Butler et al., (2014) based on a modified matrix of Nesbitt (2011). B, Ezcurra (2016). C, modified cladogram of Nesbitt & Butler, 2012 with the red lines and asterisks indicating the possible phylogenetic positions of Erpetosuchidae. Abbreviations: Arcf, Archosauriforms; Arch, Archosauria; Ps, Pseudosuchia. The Triassic outcrops of the Santa Maria Supersequence (Middle–Late Triassic) located in the central region of the Rio Grande do Sul State of southern Brazil have historically been the site of many important finds since they were first scientifically prospected in the late 1920s (Huene, 1935–1942, 1942; Beltrão, 1965). Efforts to explore these and new localities have continued during subsequent decades (Barberena, 1977; Barberena et al., 1985; Schultz, Scherer & Barberena, 2000; Da-Rosa, 2014; Horn et al., 2014; Müller et al., 2014) and have produced an ample record for many groups of archosaurs and non-archosaurian archosauriforms, such as aetosaurs (Desojo, Ezcurra & Kischlat, 2012; Da-Silva et al., 2014), doswellids (Desojo, Ezcurra & Schultz, 2011), early branch loricatans (Barberena, 1978; França, Ferigolo & Langer, 2011; Lacerda, Schultz & Bertoni-Machado, 2015; Roberto-Da-Silva et al., 2014), rauisuchids (Huene, 1935–1942; Lautenschlager & Rauhut, 2014), poposaurids (França et al., 2014), phytosaurs (Kischlat & Lucas, 2003), proterochampsids (Bertoni-Machado & Kischlat, 2003; Raugust, Lacerda & Schultz, 2013), aphanosaurians (Nesbitt et al., 2017), a possible pterosaurs (Bonaparte, Schultz & Soares, 2010; Dalla Vecchia, 2013) and several dinosauriforms (e.g. Colbert, 1970; Bonaparte, Ferigolo & Ribeiro, 1999; Langer et al., 1999; Leal et al., 2004; Ferigolo & Langer, 2006; Cabreira et al., 2011, 2016; Pinheiro, 2016). In the present contribution, we add to this record by describing a new taxon. This increases the diversity of archosaur lineages for the Triassic of this region by presenting the first occurrence of a member of the Erpetosuchidae in South America, which, in turn, gives rise to interesting questions on the paleobiogeographical distribution and evolution of this clade. Erpetosuchidae was proposed by Watson (1917) to include Erpetosuchus granti, which was described by Newton (1894) based on specimens from the Lossiemouth Sandstone Formation (late Carnian–Norian/Late Triassic), Scotland, which recognized its relationship within Archosauria, possibly closer to phytosaurs and aetosaurs, but also displaying some similarities to crocodilians (Benton & Walker, 2002). Huene (1939) described Parringtonia gracilis from the Lifua Member of the Manda Beds of Tanzania (latest Anisian/Middle Triassic) and referred it to Pseudosuchia, acknowledging some of its similarities to Ornithosuchus woodwardi Newton, 1894 (sensuvon Baczko & Ezcurra, 2016) and Saltopus elginensis (Huene, 1910), but considered the preserved material insufficient to determine whether the taxon was closely related to these taxa or if instead it represented a new pseudosuchian lineage. Similarities on the scapulae of Parringtonia and Erpetosuchus were noted by Krebs (1965), but the inclusion of both taxa in a single group was proposed in several articles by Walker (1961, 1968, 1970), with a formal diagnosis of Erpetosuchidae only provided later by Krebs (1976), which retained both taxa. The removal of Parringtonia from this group was proposed by Benton & Walker (2002), suggesting that the similarities were possible plesiomorphies. An incomplete specimen (AMNH 29300) is referred to Erpetosuchus sp. by Olsen, Sues & Norell (2000) from the Late Triassic (Norian) New Haven Formation of Connecticut, USA. Lastly, Nesbitt & Butler (2012) phylogenetically defined Erpetosuchidae as a branch-based clade that includes Parringtonia and Erpetosuchus, but displayed a poor resolution within Archosauria (Fig. 1C) In addition, Dyoplax arenaceus Fraas, 1867 (Maisch, Matzke & Rathgeber, 2013) from the Schilfsandstein Formation (early Carnian/Late Triassic) of Germany, was proposed by Walker (1961, 1968, 1970) as a member of the Erpetosuchidae. The phylogenetic position of this taxon has been greatly debated, having been considered closer to Aetosauria (Huene, 1903), Erpetosuchidae (Walker, 1961, 1968, 1970; Maisch et al., 2013) or Crocodylomorpha (Lucas, Wild & Hunt, 1998; Benton & Walker, 2002). In the analysis by Nesbitt & Butler (2012), Dyoplax was not included because these authors concluded that the taxon did not display clear erpetosuchid features, although they did not completely exclude the possibility, considering its overall morphology. However, this would require a better understanding of its osteology, which is possible only with the discovery and study of new materials. MATERIAL AND METHODS The specimen is composed of a single mostly complete but badly preserved skull with mandibles, associated with some postcranial elements (holotype MMACR PV 036-T). Most of the description and comparative osteological study is based on the structures present on the right side of the skull, which is better preserved. Measurements of the specimen are provided in Appendix section. Preparation of the specimen was undertaken using mechanical chisels and microtools at the start of its study by one of the authors (M.B.L.). However, owing to its hardened preservation, especially of the underlying rock matrix, mechanical preparation was very limited, and most of the ventral portion of the fossil remained concealed by the matrix. Computed tomography (CT) was used to view inaccessible areas, such as the palatal region, and to deduce the number of alveoli on the jaws. The specimen was scanned at the Serpal Clínica de Diagnósticos, Porto Alegre, Brazil, under a medical GE Light Speed Machine with the following settings: slice thickness of 1 mm, slice increment (interslice spacing) of 0.6 mm, field of view of 250 mm, 120 kV and 150 mA. The data were output from the scanner in DICOM format. The type locality is unknown. The specimen was donated to the Museu Municipal Aristides Carlos Rodrigues in the Municipality of Candelária (MMACR) by a local citizen who requested, emphatically, to remain anonymous and did not reveal the place of the discovery. The only information that was provided to the museum curator was that the fossil was discovered 20 years ago at the margin of one of the many artificial ponds (‘açudes’) that exist in that region. The donor collected the specimen not considering it to be a fossil but an ‘odd, skull-shaped rock’ and subsequently used it as a curiosity piece in his living room for the following two decades. Then, on Christmas Day 2013, he donated it to the local museum (MMACR). This was probably motivated by an increase in the interest on fossils and prehistoric life by the citizens of the town and neighbouring region in response to efforts by the local museum curator and staff. The preservation pattern provided a clue to its origin, at least at the biostratigraphical level, because it matched the fossil preservation of specimens from the Dinodontosaurus Assemblage Zone (Holz & Schultz, 1998), but further support was needed. A rare earth element (REE) analysis was chosen to test this inference, because this methodology has been used successfully to establish specimen origins (e.g. Lukens, Grandstaff & Terry, 2009; Suarez, Macpherson & Grandstaff, 2009). Samples were collected from the studied specimen and from an unprepared and undescribed dicynodont deposited in the collection of the Laboratório de Paleovertebrados of the Universidade Federal do Rio Grande do Sul, which was discovered in the ‘Sanga Pascual’ outcrop near the Municipality of Candelária and which has been biostratigraphically established as belonging to the Dinodontosaurus Assemblage Zone (Barberena, 1977; Schultz et al., 2000). The samples were prepared according to the standard methodology and sent to Activation Laboratories Ltd, Ancaaster, ON, Canada, where they were subjected to a UT-7 sodium peroxide fusion (ICPMS) analytical package. The results were included in a database of REE samples from fossil-bearing outcrops of major sedimentary basins in Brazil that is currently in the final stages of construction at the Setor de Geociências at the Universidade Federal do Rio Grande do Sul (UFRGS) by P. A. V. Paim and V. P. Pereira under the advisement of M. B. Soares (see Supporting Information Appendix S1). The results indicated a close match with samples of the Santa Maria Supersequence and especially of the Dinodontosaurus Assemblage Zone, but displayed a signature that did not match that of any outcrop that was included in the database, thus indicating that the fossil was not discovered in any of the more well-known sites. The full description of the methods used and the results are presented in Supporting Information Appendix S1. Institutional abbreviations BSPG, Bayerische Staatssammlung für Paläontologie und Geologie and Department of Earth and Environmental Sciences, Munich, Germany; CPEZ, Coleção de Paleontologia do Museu Paleontológico e Arqueológico Walter Ilha, São Pedro do Sul, Brazil; MCN, Museu de Ciências Naturais da Fundação Zoobotânica do Rio Grande do Sul, Porto Alegre, Brazil; MMACR, Museu Municipal Aristides Carlos Rodrigues, Candelária, Brazil; NHMUK, The Natural History Museum, London, UK; PULR, Museu de Ciencias Naturales, Univerisdade Nacional de La Rioja, La Rioja, Argentina; PVL, Paleontología de Vertebrados, Instituto ‘Miguel Lillo’, San Miguel de Tucumán, Argentina; PVSJ, División de Paleontología de Vertebrados del Museo de Ciencias Naturales y Universidad Nacional de San Juan, San Juan, Argentina; SAM, Iziko South African Museum, Cape Town, South Africa; SMNS, Staatliches Museum für Naturkunde Stuttgart, Stuttgart, Germany; UFRGS-PV, Laboratório de Paleovertebrados da Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil. SYSTEMATIC PALEONTOLOGY Archosauria Cope, 1869 sensu Gauthier & Padian (1985,) Pseudosuchia Zittel, 1887–1890 sensu Gauthier & Padian (1985,) Erpetosuchidae Watson, 1917 sensu Nesbitt & Butler (2012) Pagosvenator candelariensis gen. et sp. nov. urn:lsid:zoobank.org:act:59A6DE11-4370-4C5F-8CD9-DAF8E54C616B urn:lsid:zoobank.org:act:FE81FC65-99DC-4475-8978-0E49FE481C25 Etymology: ‘Pagos’ is a regional gaucho jargon term (sometimes used in the singular, pago, but its plural use is more common) that is derived from the Latin ‘pagus’, meaning ‘countryside’ or ‘rural community’; ‘venator’ is Latin for ‘hunter’ owing to it being a relatively large carnivore; and ‘candelariensis’ is with regard to the city of Candelária, where the museum in which the specimen is deposited is located. The name means ‘the hunter from the surroundings of Candelária’. Holotype: MMACR PV 036-T; mostly complete and articulated skull and lower jaws, associated with two incomplete vertebrae and five heavily ornamented osteoderms. Diagnosis: Pseudosuchian (Erpetosuchidae) archosaur, with the following unique combination of characters states: four premaxillary teeth; maxilla with an edentulous posterior half, large and posteriorly deep antorbital fossa and a posteriorly positioned antorbital fenestra relative to the anteroposterior length of the rostrum; ascending process of the jugal bifurcates dorsally into a V-shaped structure that composes the ventral margin of the orbit; lacrimals do not contribute to the skull roof; palpebral bones; slightly longer than wide osteoderms with heavily ornamented dorsal surfaces, displaying small pits and short ridges. Type locality and age: The locality is unknown (see the previous section and the Supporting Information Appendix S1). The type of preservation of the specimen with a supporting REE analysis indicates that it belongs to a site from the Dinodontosaurus Assemblage Zone, Middle-Late Triassic (late Ladinian–earliest Carnian age), whose outcrops are placed south of the city of Candelária. Description Skull overview The skull of P. candelariensis suffered taphonomic alterations, with the majority of the elements that form the infratemporal fenestra being altered, in the case of the left side, or lost, in the case of the right side (Fig. 2). The anterior part of the rostrum was damaged and rotated 15° clockwise. The right side of the skull displays major distortions, with many elements, specifically the ones that form the ventral margin of the maxilla, the posteroventral border of the orbit and the infratemporal fenestra, being displaced or lost. Some suture patterns are also distorted, which results in some paired elements not displaying mirrored features. Figure 2. View largeDownload slide A–H, images generated by computer tomography of MMACR PV 036-T, presenting the different portions of the specimen and some of the preservational alterations that the specimen suffered: dorsal (A, B), ventral (C, D), left lateral (E, F) and right lateral (G, H) views. Colorized models are not to scale. Figure 2. View largeDownload slide A–H, images generated by computer tomography of MMACR PV 036-T, presenting the different portions of the specimen and some of the preservational alterations that the specimen suffered: dorsal (A, B), ventral (C, D), left lateral (E, F) and right lateral (G, H) views. Colorized models are not to scale. The premaxilla is formed by a subquadrangular main body, a gracile anterodorsal process and a narrow posterodorsal process. Although both premaxillae are morphologically similar, the right one is distorted and dorsoventrally shorter owing to a heightened ventral curvature. In lateral view, the anterior margin of the main body is sub-vertical, with an anteroventral margin that is recurved up to the remains of the first premaxillary tooth (Fig. 3). This margin displays a small posterodorsal curvature that ends at the base of the anterodorsal process, which was initially interpreted by Lacerda, França & Schultz (2016) as similar to the condition found in Ornithosuchidae. This posteroventral curvature was extended dorsally because of the compression of the anterior portion of the rostrum, which artificially created an ornithosuchid-like ‘downturned’ condition. The dorsal third of the body of the premaxillae is more medially compressed, forming a marked fossa that forms the anteroventral border of the external naris. Figure 3. View largeDownload slide A, B, photograph (A) and interpretive illustration (B) of specimen MMACR PV 036-T in left lateral view. Abbreviations: AFO, antorbital fossa; AN, angular; AOF, antorbital fenestra; AR, articular; AV, alveoli; F, frontal; FPMX, premaxillary fossa; J, jugal; LA, lacrimal; MSH, mandibular shelf; N, nasal; OR, orbit; PA, parietal; PAL, palpebral; PF, prefrontal; PMX, premaxilla; PO, postorbital; QJ, quadratojugal; SQ, squamosal; SU, surangular; T, teeth; ?, unidentified bone fragments. Concretions are in dark grey, cranial openings in black, and broken areas are crosshatched. Figure 3. View largeDownload slide A, B, photograph (A) and interpretive illustration (B) of specimen MMACR PV 036-T in left lateral view. Abbreviations: AFO, antorbital fossa; AN, angular; AOF, antorbital fenestra; AR, articular; AV, alveoli; F, frontal; FPMX, premaxillary fossa; J, jugal; LA, lacrimal; MSH, mandibular shelf; N, nasal; OR, orbit; PA, parietal; PAL, palpebral; PF, prefrontal; PMX, premaxilla; PO, postorbital; QJ, quadratojugal; SQ, squamosal; SU, surangular; T, teeth; ?, unidentified bone fragments. Concretions are in dark grey, cranial openings in black, and broken areas are crosshatched. The anterodorsal process is narrow and articulates posterodorsally between two anteroventral projections of the nasals in a V-shaped contact (Fig. 3), similar to the one described in O. woodwardi (Walker, 1964) and Riojasuchus tenuisceps (PVL 3827; Bonaparte, 1967; von Bazcko & Desojo, 2016). This area is ventrodorsally compressed, which has altered its dimensions and most of the dorsal border of the naris, which is slightly reduced in height but not overall form. The posterodorsal process of the premaxilla has a wide base that tapers posteriorly, with its most posterior end articulating between two ventral processes of the nasal and ending posterior to the nasal opening. This process is greater than the anteroposterior length of the main body of premaxilla, similar to Gracilisuchidae and early branch loricatans and different from the comparatively smaller process in E. granti (NHMUK R3139), Ornithosuchidae (NHMUK PV R3143; PVL 3827) and Aetosauria (e.g. SMNS 5770) (Nesbitt, 2011; Nesbitt & Butler, 2012). The posterodorsal process is better observed in dorsal view, because in lateral view, owing to the above- mentioned alteration of this region of the skull, it appears as a smaller, acute process. Its distal end fits into a slot in the nasal, similar to Revueltosaurus callenderi (Hunt, 1989; Parker et al., 2005) and Gracilisuchidae (Butler et al., 2014). Tooth remains are preserved on the anterolateral and ventral portions of the rostrum, but only the two on the left premaxilla are preserved in their sockets, with the most posterior one being the better preserved. The above-mentioned alteration in the ventral curvature damaged most of the area, and its remains were preserved in a large concretion mixed with bone and tooth fragments that obscures most of this area. The number of alveoli was determined only by CT scans, which revealed four in each premaxilla (Fig. 4). The number of premaxillary teeth is variable in pseudosuchians. Four teeth are in E. granti (NHMUK R3139), Aetosaurus ferratus (SMNS 5770; Schoch, 2007), Gracilisuchus stipanicicorum Romer, 1972 (Butler et al., 2014) and early branch taxa of Loricata, whereas some taxa, such as Stagonolepis robertsoni Agassiz, 1844, Revueltosaurus callenderi, Turfanosuchus dabanensis Wu, Lui & Li, 2001 and Yonghesuchus sangbiensis Wu & Russell, 2001 bear five teeth, and O. woodwardi and R. tenuisceps have three teeth in the premaxilla (Walker, 1961, Nesbitt, 2011; Nesbitt & Butler, 2012). Figure 4. View largeDownload slide A, B, detail photograph (A) and interpretative drawing (B) of the rostral region of MMACR PV 036-T in ventral view. Arrows indicate the fracture points of the anterior tips of the mandibles. C, computed tomography capture of the same region, in ventral view, indicating the number of alveoli on the premaxilla and the first maxillary tooth immediately after the premaxilla–maxilla contact. Abbreviations: L mand, left mandible; MX, maxilla; PMX, premaxilla; R mand, right mandible; t, teeth; I–IV, premaxillary teeth; I(mx), first maxillary tooth; pmx/mx, contact between the premaxilla and maxilla. Concretions are in dark grey, and broken areas are crosshatched. Figure 4. View largeDownload slide A, B, detail photograph (A) and interpretative drawing (B) of the rostral region of MMACR PV 036-T in ventral view. Arrows indicate the fracture points of the anterior tips of the mandibles. C, computed tomography capture of the same region, in ventral view, indicating the number of alveoli on the premaxilla and the first maxillary tooth immediately after the premaxilla–maxilla contact. Abbreviations: L mand, left mandible; MX, maxilla; PMX, premaxilla; R mand, right mandible; t, teeth; I–IV, premaxillary teeth; I(mx), first maxillary tooth; pmx/mx, contact between the premaxilla and maxilla. Concretions are in dark grey, and broken areas are crosshatched. The maxilla is divided in a subrectangular main body and a dorsoventrally tall and anteroposteriorly wide ascending process. The anterior portion, which articulates with the premaxilla, in dorsal view has a marked transverse expansion, which is mirrored in both maxillae, a condition that is uncommon in archosaurs but is described in P. gracilis (NHMUK R8646; Nesbitt & Butler, 2012). In lateral view, the main body is dorsoventrally expanded, and both anterior and posterior areas display similar dorsoventral depths. The premaxilla–maxilla suture is tightly closed, not displaying any foramina or accessory openings, and not displaying a diastema between the elements, unlike Ornithosuchidae (NHMUK PV R3143; PVL 3827). The anterior margin is rounded, slopping posterodorsally into the anteroposteriorly elongated ascending process. This process articulates posteriorly between the nasal and posteroventrally with the anterodorsal and anterior margins of the lacrimal. The posterior portion forms the majority of the anterior margin of the antorbital fenestra. The anterior portion of the ventral margin is straight, up to the area where the rostrum is damaged. From there, it is slightly concave, and the ventral area with the alveoli is more laterally projected. This projection was probably caused by taphonomic compression. On the posterior end of this margin, there is a small posteroventral process that extends 8 mm beyond the articulation with the jugal. The posterior process of the maxilla has almost the same dorsoventral height on the posterior region, not tapering as in Ornithosuchidae (NHMUK PV R3143; PVL 3827) or expanding as in E. granti (NHMUK R3139) and P. gracilis (NHMUK PV R8646) (Nesbitt & Butler, 2012). However, the mediolateral length is greater than the dorsoventral height on the level of the main body of the lacrimal, a characteristic shared with E. granti and P. gracilis (Nesbitt & Butler, 2012). The antorbital fossa occupies most of the lateral surface of the maxilla. This fossa gradually deepens posteriorly, reaching its deepest point close to the ventral area of the lacrimal and the anterior margin of the jugal. The antorbital fenestra is half the anteroposterior length of the fossa and is posteriorly located on the rostrum. It is subtriangular but very dorsoventrally compressed, almost to the point of a slit, with a rounded anterior tip, and displays a 25° dorsoventral inclination with regard to the central axis of the maxilla. The nearly pointed anterior margin of the antorbital fenestra is shared with Erpetosuchus and some ornithosuchid taxa (Venaticosuchus rusconi and R. tenuisceps), but a gently rounded anterior margin is observed in O. woodwardi (Nesbitt & Butler, 2012; von Baczko et al., 2014; von Baczko & Desojo, 2016; von Baczko & Ezcurra, 2016). Owing to the lateral distortion of the ventral margin of the left maxilla, the posterior third of this element is turned laterally, exposing the ventral margin, with five concretion-filled alveoli and an edentulous posterior region after the last alveolus. Computer imaging identified teeth starting immediately posterior to the articulation with the premaxilla, so at least six maxillary teeth would be present. With the exception of archosaurs that have a more specialized maxilla for herbivory (e.g. poposaurids), an edentulous posterior region of the maxilla is described only in Erpetosuchidae (Nesbitt, 2011; Nesbitt & Butler, 2012). However, this would differ from P. gracilis, which has only five, and E. granti, which has four, but is similar to the possible nine maxillary teeth inferred for a specimen attributed to Erpetosuchus sp. (AMNH 29300; Olsen, Sues & Norell, 2000). All teeth are badly preserved, being incomplete or covered in a thick layer of concretion. The two largest teeth are on the ventral border of the right maxilla, and three disarticulated teeth are preserved along the underlying lateral face of the left mandible. The teeth are anteroposteriorly recurved and lateromedially compressed, and there is no indication of any serrations (Fig. 3). The nasals are anteroposteriorly elongated elements that form the majority of the anterodorsal and dorsolateral surface of the rostrum, with both elements articulating medially. The dorsal surface is smooth and continues the length of the skull roof, with no indication of a convexity or ‘roman nose’-like feature as in Decuriasuchus quartacolonia (MCN PV10.105a; França et al., 2011; França, Langer & Ferigolo, 2013). The anterior portion, in lateral view, is anteroventrally curved and divided into two processes. The anteroventral process forms the majority of the dorsal and posterodorsal border of the external naris and contacts the dorsal tip of the anterodorsal process of the premaxilla, and it extends laterally and anteroventrally up to half its length. The posteroventral process is comparatively short and narrow. It articulates with the posterodorsal process of the premaxilla, forming a depressed area for this contact, with a piece of the process occupying an area between the premaxilla and maxilla. The main body of the nasal forms the anterior portion of the skull roof, with a broad mediolateral length, whereas the posterior process is located on its medial half and posteriorly tapering along the articulation with the frontal. The nasal has a broad contact with the prefrontal, on the posterior margin of the main body and the anterolateral region of the posterior process, unlike in Ornithosuchidae, where these bones do not meet (Walker, 1964; von Baczko & Ezcurra, 2013; von Bazcko & Desojo, 2016). In addition, Pagosvenator does not share with the Gracilisuchidae and some loricatans (e.g. Rauisuchidae) the nasal contribution to the antorbital fossa (Nesbitt, 2011; França et al., 2013; Butler et al., 2014). The lacrimal is divided into two processes; an anterior L-shaped process that is anteroposteriorly inclined, and a posteroventral process that forms three-quarters of the anterior margin of the orbit (Fig. 3). This bone is completely covered dorsally, lacking any contribution to the skull roof. The anterior process delimits the posterior half of the dorsal and all the posterodorsal margins of the antorbital fossa, along with the posterodorsal margin of the antorbital fenestra. It forms, with the prefrontal and the jugal, a thick anterolateral expansion or ridge along the extent of the antorbital bar. This ridge forms a deep pocket on the posterodorsal end of the fossa, similar to the one in R. tenuisceps, some theropods and basal saurischians (Nesbitt, 2011; von Bazcko & Desojo, 2016 but it displays a more lateral expression, although this may have been artificially deepened as a result of the distortion already described. The prefrontal is a wide element of the skull roof, with a discrete presence on the lateral view (Figs 2, 3). It articulates anteromedially with the nasals, posteromedially with the frontal and ventromedially with the jugal, forming most of the anterior border of the orbit. Its anterior portion is not in articulation with the rostrum anteriorly, owing to the distortion that this part of the skull suffered, which is indicated by a transverse fracture on the anterior portion of both prefrontals, but would indicate the overall aspect of the anterior margins. In dorsal view, it is subrectangular, with a straight anterior margin, a convex posterior margin and a small lateral process that covers the lacrimal ventrolaterally. The dorsal surface displays a deep fossa that is mirrored on both elements. This fossa is lateral to the anterior processes of the frontal and is near an area that displays a large number of fossae and ridges that appear not to be formed by taphonomic alterations, which would indicate a heavily ornamented region of the skull roof. The lateroventral process, along with the posterodorsal region of the lacrimal, forms a bar that delimits posterodorsally the deepest part of the antorbital fossa. The frontal is a wide, dorsoventrally compressed element that articulates anteriorly with the nasals by two narrowing anterior processes, anterolaterally with the prefrontal along a sinuous contact, posterolaterally with the postorbital and posteriorly with the parietal along a lateromedially wide U-shaped process (Fig. 3). In anterior view, the lateral portion near the orbits displays a marked dorsal curvature, and its surface is marked by deep pits and ridges that are mirrored on both sides of the element and continue up to the palpebrals. The frontal makes up the dorsal border of the orbit and articulates lateroposteriorly with a palpebral element, which is better observed on its right side. The presence of a single frontal and the rare pattern of the nasal–frontal suture in archosaurs matches the condition described for E. granti (Benton & Walker, 2002), but in P. candelariensis this region of the skull roof is more lateromedially wide, whereas in the former it is more constrained. No longitudinal ridge along the midline or the anterior portion tapering anteriorly is observed in P. candelariensis, differing from Gracilisuchidae and some early branch loricatans in that these features are present (Nesbitt, 2011; Nesbitt & Butler, 2012). The right palpebral is mostly preserved, with the left one represented only by its medial portion that is still in articulation with the other elements on the dorsal margin of the orbit along a large fracture. Most of this damaged area corresponds to that which is occupied on the left side by the other palpebral and the dorsal portion of the postorbital. Additionally, the palpebral articulates posteromedially with the postfrontal and posteriorly with the postorbital. In dorsal view (Fig. 3), its shape is subrectangular, with a thick and rugose lateral margin, whereas the dorsal surface displays a series of pits and the lateral continuation of some ridges that arise on the frontal. The presence of a palpebral element is described in aetosaurs, loricatans, poposaurids, crocodylomorphs and ornithischians, with its overall morphology varying greatly between different groups, within the same taxon and during ontogeny (Nesbitt, Turner & Weinbaum, 2013b) but the palpebrals of the described specimen appear distinct, because no sub-rectangular element, in dorsal view, with shallow pits has been described. The postfrontal, in dorsal view, is an irregular bone that articulates anterolaterally with the palpebral, anteriorly and anteromedially with the frontal, posteromedially with the parietal and posterolaterally with the postorbital. As such, it does not participate in the margin of the orbits, but its convex posterior margin forms most of the anterior border of the supratemporal fenestra. Its overall irregular form, in dorsal aspect, differs from that of most of the postfrontals described in basal suchians, but its participation in the skull roof, with its posterior border forming the anterior margin of the supratemporal fenestra region, is similar to the ones in Riojasuchus (PVL 3827; von Baczko & Desojo, 2016). The left postorbital is mostly preserved and divided into an incomplete dorsal portion and a ventral portion, whereas the right postorbital is represented by only a fragment of the anterior portion. In dorsal view, it is anteroposteriorlly elongated, with its anterior region being mediolaterally expanded with a short mediolateral process. This anterior region articulates with the lateral margin of the postfrontal, and its main body forms the lateral margin of the supratemporal fenestra, which ends in a narrow posterior process that is turned lateromedially up until its broken tip. The anterior contact of the ventral portion articulates along the damaged area of the palpebral, whereas its main body projects anteroventrally and forms the posterodorsal and posterior border of the orbit. The posterior process that contacts the squamosal is mostly restricted dorsally, unlike aetosaurs, Gracilisuchus and Yonghesuchus, where it is ventrally broad. The ventral process of the postorbital in Pagosvenator is similar in length to the jugal in the composition of the postorbital bar. Only the left squamosal is preserved, and it is divided into two segments (Figs 2, 3). The first is anteriorly displaced and is ventrally displaced to the dorsal portion of the postorbital. It displays an anteroposteriorly wide dorsal section that has on its anterodorsal surface a shallow fossa for the articulation of the posterior portion of the postorbital and an anteroposteriorly curved ventral process that contacts the postorbital ramus of the ascending process of the jugal, near the articulation of this element with the ventral process of the postorbital. Owing to the damage suffered by the posterior region of the skull, it is twisted 30° anticlockwise and displaced more anteriorly, between the anterior and posterior ramus of the posterior process of the jugal. As a result of this distortion, it occupies an area equivalent to the infratemporal and exposes only two small lateral openings. The second piece is a small fragment of the posteromedial region that is positioned more posteriorly and is in articulation with the paraoccipital process of the braincase. The dorsal surface of the squamosal on the supratemporal fenestrae is smooth, without any ridges or marked edges. The ventral process lacks the lateral ridge or the anteroventral projection found in some loricatans, such as Saurosuchus galilei (PVSJ 32; Alcober, 2000) and Prestosuchus chiniquensis (UFRGS-PV-0156-T; Barberena, 1978; Azevedo, 1991). The parietal is a single element, with no indication of a parasagittal suture, similar to the condition of the frontal (Fig. 5). In dorsal view, its main body is subrectangular and dorsoventrally flat, with an anterior portion formed by two anterolateral processes that form, anteriorly, a sub-circular contact with the frontal and articulate anterolaterally with the postfrontals. Two elongated, anterolaterally compressed, posterolateral processes are present, projecting from the posterior half of the main body, and form occipital flanges, similar to O. woodwardi (NHUMK R2409; Walker, 1964). However, this process is nearly vertical, whereas in Ornithosuchidae and aetosaurs this process is > 45° inclined anteriorly. The left one is preserved, but the right has been damaged, preserving only the fragments closer to the contact with the occipital. The presence of a single parietal is uncommon in archosauriforms, being described in Erpetosuchus and in some crocodylomorphs. However, as observed in the modern taxa of the latter group, the parietal can arise as two separate elements and fuse during late ontogeny (Rieppel, 1993), although it is impossible to infer whether this was the case in the present specimen. The jugal is a triradiated element, divided into a main body, with anterior, dorsal and posterior processes. The posterior process is broken into two segments owinng to the collapse of the area of the infratemporal fenestra and disarray of the quadratojugal–jugal articulation. The anterior process is anteroposteriorly short and articulates with the main body of the maxilla, forming the posterior rim of the antorbital fossa and the posterior margin of the antorbital fenestra, a condition that is also described in Proterosuchus fergusi, some proterochampsids, phytosaurs, ornithosuchids, sauropodomorphs and ornithischians (Nesbitt, 2011; von Baczko & Desojo, 2016; Ezcurra, 2016). However, the closest match is the one described in Erpetosuchus (Benton & Walker, 2002), which displays a jugal with five processes, but with its two anterior processes forming a posterior limit to a deep antorbital fossa, which is morphologically the closest to the one in Pagosvenator. The dorsal process is divided into preorbital and postorbital rami, which form the ventral margin of the orbit and have a distinct V-shaped aspect in lateral view, like the one described in Erpetosuchus (Benton & Walker, 2002) and in ornithosuchids, but is ventrally more rounded like the one in the Riojasuchus, compared with the more acute one in Ornithosuchus (von Baczko & Desojo, 2016). The preorbital ramus articulates with the lacrimal along a broad vertical suture, whereas the postorbital ramus contacts the postorbital bone. A large area of damage is present on the lateral portion of the main body and on most of the posterior process. A longitudinal ridge is present on the lateral surface of main body of the jugal in Pagosvenator, although it does not display a bulbous appearance, such as those in rauisuchids (e.g. Gower, 1999; Lautenschlager & Rauhut, 2014). The posterior process is broken into two segments; its anterior part is wedge shaped in lateral view and positioned more posteroventrally, whereas the posterior portion is preserved in articulation with the quadratojugal on the dorsal margin of the mandible. This articulation is similar to the one in Riojasuchus and Ornithosuchus (Walker, 1964; von Bazcko & Desojo, 2016), but taphonomic alterations have twisted this area dorsolaterally, displaying the ventral area where the quadratojugal articulates with the jugal along a wide, rounded contact. The posterior process is dorsal to the quadratojugal on this contact, with posterior limits anterior to the posterior margin of lower temporal fenestra, unlike Erpetosuchus, Gracilisuchus and Yonghesuchus in that the process is located posterior to the fenestra. The elements of the posterolateral regions of the skull have suffered major displacement, whereas most of the elements of the right side have been lost. The quadratojugal is represented by only the posterior portion of the left element, with only its posterior half visible owing to the swivel of the ventral bar of the infratemporal fenestra. In dorsal view, it is an anteroposteriorly wide, subrectangular bone, with a sinuous lateral margin and a mediolaterally broad posterior region, which has a small fracture on its lateral margin. In lateral view, it articulates with the posterior process of the jugal along an anteriorly directing V-shaped suture and medially with the posterior region of the quadrate. Despite the taphonomic bias, the quadratojugal is not dorsally expanded, occupying < 80% of the posterior border of the lower temporal fenestra, unlike Erpetosuchus, Gracilisuchidae and aetosaurs. The quadrate is an anteroposteriorly elongated bone which, owing to the disarticulation of the posterior elements of the skull, is more anteriorly located, where its anterior portion is positioned lateral to the braincase and twisted dorsally (Fig. 3). It articulates laterally with the quadratojugal, with a small foramen between the two elements in its central portion. Its posterior tip is mediolaterally expanded along a straight margin of the articular condyle. The right lateral and ventral portion of the occipital region is covered by concretions and osteoderm fragments, also obscuring most elements of this side of the skull and completely covering the foramen magnum (Fig. 6). The supraoccipital, in posterior view, is a dorsoventrally short but lateromedially wide subtriangular element. It articulates dorsally with the parietal along its posterolateral processes, ventrolaterally with the opisthotic and ventrally with the exoccipitals. The dorsal surface of its main body is smooth, with no indication of a ridge or process. Only the proximal portion of the opisthotic is preserved, with a reduced posterolaterally projecting paraoccipital process that ends on a fragment of a medial portion of the squamosal. Owing to an accumulation of osteoderms on the right side of the ventral portion of the supraoccipital, only the left exoccipital is visible. It is a small, quadrangular element in posterior view, which is tightly fused anteriorly with the supraoccipital and anterolaterally with the opisthotic. Mandibles Both mandibles are present but not in articulation with the skull, being positioned under and roughly inside the mouth cavity. This placement made it impossible to visualize the tooth-bearing dorsal margin of the mandibles, and CT scans proved unreliable to provide useful information. The anterior tips of the mandibles were fractured along with the rest of the rostrum and also dislocated, with the right piece being displaced more medially and the left one more laterally, covering the region posterior to where the fracture occurred (Fig. 4). The left mandible is twisted, with its lateral face placed dorsolaterally, whereas only the ventral portion of the right mandible is visible outside the mouth cavity. Owing to these alterations, all of the medial regions of the mandibles, with the exception of the posteriormost region of the left one, are impossible to observe. Although mostly covered by the skull and distorted, the presence of a mandibular fenestra is not clear, but this is because the posterior portion of the left mandible is covered by the jugal and associated unidentified bone fragments, although the shape of mandibular bones (posterior end of dentary; anterior end of surangular and angular) indicate its presence, but its exact appearance and dimensions are impossible to establish. The dorsoventral height of the dentary is unknown owing to the obstruction of the dorsal margin. Its visible surface, ventral to the posterior area of the maxilla, indicates a dorsoventrally expanded and anteroposteriorly elongated element, which is dorsoventrally reduced anteriorly with a smooth, rounded ventral margin of the anterior tip of the mandible. Its posterodorsal margin has a short dorsal process that meets a concretion that is also at the ventral base of the squamosal, posterolaterally with the surangular and posteroventrally with the angular. The surangular is a mediolaterally compressed element that displays a dorsoventrally short anterior portion that expands posteriorly up to two-thirds of its length. It extends posteriorly, forming the majority of the posterior portion of the mandible, and almost completely excludes the articular in lateral view. This condition where the surangular completely obscures the articular laterally is similar to the one described in the loricatan Batrachotomus kupferzellensis (Gower, 1999), the paracrocodylomorph Postosuchus kirkpatricki (Weinbaum, 2011) and in Erpetosuchus (Benton & Walker, 2002), but in the latter taxon this must be considered with reservations because it is inferred based on casts that might not preserve more delicate sutures. It displays a sharp lateral shelf formeds along the anteroposterior length of its dorsal surface, with an underlaying fossa that runs ventral to the shelf. In dorsal view, the articular is a triangular element that articulates laterally with the surangular, which excludes it almost entirely from the lateral portion of the hemimandible. Its anterior portion presents an anteroposteriorly wide, concave glenoid fossa, which is covered in a thick concretion, but lacks any transverse ridge, aside from a small dorsal projection on the end of its medial portion. The medial process is present and robust, but does not present any foramen as in the Batrachotomus and Decuriasuchus (Gower, 1999; França et al., 2013). The retroarticular region displays an angled posterior process, with a longitudinal ridge that extends the posterior margin of this element dorsoventrally. Owing to the preservation of the medial portion of the mandible, it is impossible to interpret the form and sutures of the prearticular and coronoid bones. A number of unidentified fragments are observed on the left side of skull. The most anterior one is elongated, narrow and is positioned on the posterior region of the dentary. The second one covers the lateral side of angular, with a semicircular posterior region and a broken anterior facet. Considering the anatomical position, both bones could be skull fragments, but their poor preservation prevents a clear identification. Postcranial elements The remains of two articulated vertebrae lying on their right sides were preserved behind the occipital region of the skull (Fig. 5). One vertebra is represented only by its neural spine and left postzygapophysis, whereas the second has a complete sub-rectangular vertebral body and ventral portion of the neural arch, with the left prezygapophysis in articulation with the corresponding postzygapophysis of the adjacent preserved vertebra. Figure 5. View largeDownload slide A, B, photograph (A) and interpretive drawing (B) of MMACR PV 036-T in dorsal view. Abbreviations: AR, articular; AFO, antorbital fossa; CEN, centrum; EX, exoccipital; FO, quadratojugal–quadrate foramen; FPMX, premaxillary fossa; FR, frontal; J, jugal; MX, maxilla; N, nasal; NS, neural spine; OP, opisthotic; OR, orbit; OST, osteoderm; PA, parietal; PAL, palpebral; PF, prefrontal; PMX, premaxilla; PO, postorbital; POF, postfrontal; POZY, postzygapophysis;. PRZY, prezygapophysis; Q, quadrate; QJ, quadratojugal; SO; supraoccipital; SQ, squamosal; UTF, upper temporal fenestra. Concretions are in dark grey, cranial openings in black, and broken areas are crosshatched. Figure 5. View largeDownload slide A, B, photograph (A) and interpretive drawing (B) of MMACR PV 036-T in dorsal view. Abbreviations: AR, articular; AFO, antorbital fossa; CEN, centrum; EX, exoccipital; FO, quadratojugal–quadrate foramen; FPMX, premaxillary fossa; FR, frontal; J, jugal; MX, maxilla; N, nasal; NS, neural spine; OP, opisthotic; OR, orbit; OST, osteoderm; PA, parietal; PAL, palpebral; PF, prefrontal; PMX, premaxilla; PO, postorbital; POF, postfrontal; POZY, postzygapophysis;. PRZY, prezygapophysis; Q, quadrate; QJ, quadratojugal; SO; supraoccipital; SQ, squamosal; UTF, upper temporal fenestra. Concretions are in dark grey, cranial openings in black, and broken areas are crosshatched. Six osteoderms are associated with the specimen (Figs 5, 6). Two are complete and four incomplete, with the largest and best-preserved one being rectangular (32 mm anteroposterior length and 33 mm lateromedial width). The borders are smooth, lacking an anterior process similar to the ones in aetosaurs (Nesbitt & Butler, 2012; Desojo et al., 2013) and the doswellidae Archeopelta arborensis (CPEZ-239a; Desojo et al., 2011) (Fig. 7). All osteoderms are heavily ornamented, with a dorsal surface covered with small pits and short ridges, but lacking a central anteroposteriorly extended ridge like the one in Erpetosuchus and Parringtonia (Nesbitt & Butler, 2012). Owing to the disarticulated condition of the postcranial elements, it is unclear how the osteoderms where arranged when in articulation and which section of the cervical sequence they would belong to, even though they were preserved near the skull. However, the lengths of the osteoderms are consistent with two anteroposterior segments per vertebra, probably with a paired sagittal axis. Figure 6. View largeDownload slide A, B, photograph (A) and interpretive drawing (B) of the occipital region in posterior view. Vertebral elements were removed to detail this region more clearly. Abbreviations: EX, exoccipital; FR, frontal; OP, opisthotic; OST, osteoderms; PA, parietal; PAL, palpebral; PO, postorbital; SQ, squamosal; VERT, vertebra (portions). Concretions are in dark grey, in broken areas are crosshatched. Figure 6. View largeDownload slide A, B, photograph (A) and interpretive drawing (B) of the occipital region in posterior view. Vertebral elements were removed to detail this region more clearly. Abbreviations: EX, exoccipital; FR, frontal; OP, opisthotic; OST, osteoderms; PA, parietal; PAL, palpebral; PO, postorbital; SQ, squamosal; VERT, vertebra (portions). Concretions are in dark grey, in broken areas are crosshatched. Figure 7. View largeDownload slide A, B, photographs of the best-preserved osteoderm in MMACR PV 036-T: A, in detail; and B, isolated and with heightened shadows to display the ornamentation cover better. C–F, interpretative illustrations of various ornamented osteoderms of archosauriforms for comparison: C, osteoderm of Pagosvenator candelariensis (MMACR PV 036-T); D, osteoderm of Parringtonia gracilis in dorsal view (NHMUK R3139, redrawn based on Nesbitt & Butler, 2012); E, osteoderm of Archeopelta arborensis (CPEZ-239a; redrawn based on Desojo et al., 2012); and F, osteoderm of Tarjadia ruthae (PULR 063; redrawn based on Arcucci & Marsicano, 1998). Abbreviations: AAF, anterior articular facet; CRI, central ridge; P, pit; RI, ridge. Osteoderms are not to scale. Figure 7. View largeDownload slide A, B, photographs of the best-preserved osteoderm in MMACR PV 036-T: A, in detail; and B, isolated and with heightened shadows to display the ornamentation cover better. C–F, interpretative illustrations of various ornamented osteoderms of archosauriforms for comparison: C, osteoderm of Pagosvenator candelariensis (MMACR PV 036-T); D, osteoderm of Parringtonia gracilis in dorsal view (NHMUK R3139, redrawn based on Nesbitt & Butler, 2012); E, osteoderm of Archeopelta arborensis (CPEZ-239a; redrawn based on Desojo et al., 2012); and F, osteoderm of Tarjadia ruthae (PULR 063; redrawn based on Arcucci & Marsicano, 1998). Abbreviations: AAF, anterior articular facet; CRI, central ridge; P, pit; RI, ridge. Osteoderms are not to scale. Phylogenetic Analysis The new taxon, P. candelariensis, was included in a matrix with 418 characters and 85 terminal taxa. The matrix is based on the original analysis of Nesbitt (2011), with compilations of its modified versions by Butler et al. (2011), Nesbitt & Butler (2012), Butler et al. (2014) and von Baczcko et al. (2014). Additionally, one new character is proposed, and some characters states were altered, using information based on personal study of specimens and on recently articles (full details in the Supporting Information, Appendix S2). The matrix was analysed in TNT (Goloboff, Farris & Nixon, 2008), using a heuristic search with 10000 replicates of Wagner trees, tree bisection and reconnection (TBR) branch swapping (holding 10 trees per replicate), with collapsed branch with zero length. Some multistate characters were ordered according to parameters stated in the original analysis and above-mentioned works: 32, 52, 121, 137, 139, 156, 168, 188, 223, 247, 258, 269, 271, 291, 297, 328, 356, 377, 399, 198, 416. Bootstrap and Bremer support were calculated with scripts on TNT. Additional analyses in searching for unstable taxa were conducted in TNT, using the IterPCR script proposed by Pol & Escapa (2009). The cladistic analysis resulted in 360 most parsimonious trees, with 1358 steps. Pagosvenator candelariensis was found to be a sister group of E. granti plus P. gracilis, composing the earliest diverging branch of Erpetosuchidae (Fig. 8). Figure 8. View largeDownload slide Alternative positions of Erpetosuchidae among the relationships of Pseudosuchia, indicating a simplified version of the strict consensus trees, 360 most parsimonious trees with 1358 steps, using a phylogenetic matrix composed of 84 terminal taxa and 417 (418 above) characters. Figure 8. View largeDownload slide Alternative positions of Erpetosuchidae among the relationships of Pseudosuchia, indicating a simplified version of the strict consensus trees, 360 most parsimonious trees with 1358 steps, using a phylogenetic matrix composed of 84 terminal taxa and 417 (418 above) characters. In previous analyses, this group had been considered as an unstable taxa (Nesbitt & Butler, 2012), with six possible positions: (1) earliest branch from Pseudosuchia; (2) earliest branch from Suchia (including G. stipanicicorum, T. dabanensis, Aetosauria, Paracrocodylomorpha and other related taxa); (3) sister group of T. dabanensis (not found as sister group of G. stipanicicorum in this analysis); (4) earliest branch of the Aetosauria lineage, being a sister group of the clade composed of Revueltosaurus plus Aetosauria; (5) earliest branch of the Paracrocodylomorpha lineage, being a sister group of the clade composed by Ticinosuchus ferox (Krebs, 1965) plus Paracrocodylomopha; and (6) earliest branch of Avemetatarsalia (Fig. 1C). Butler et al. (2014) considered Erpetosuchidae as a wild taxon, also revealing this unstable position in the evolution of Archosauria, with the consensus tree from this analysis being poorly resolved and displaying a major polytomy at the base of Archosauria. In the present analysis, the strict consensus (see Supporting Information, Appendix S1, S2) reveals a similar topology. However, there is a polytomy at the base of the pseudosuchian lineage, formed by Erpetosuchidae, Ornithosuchidae, the clade composed by Revueltosaurus plus Aetosauria, and the clade composed by Gracilisuchidae plus T. ferox and Paracrocodylomorpha. Accordingly, the alternative positions of Erpetosuchidae as a sister group of T. dabanensis or an early branch of Paracrocodylomorpha or an early branch of Avemetatarsalia were not supported with this analysis. Furthermore, the result of unstable taxa analysis (Pol & Escapa, 2009) excluded the alternative position of Erpetosuchidae as an early branch of Pseudosuchia or an early branch of the Aetosauria lineage (sister group of Revueltosaurus plus Aetosauria). The results of the analysis reveal, before one iteration, only two possible positions of Erpetosuchidae among the most parsimonious trees: as a sister group of Ornithosuchidae, composing an early branch lineage of Pseudosuchia, or a sister group of the clade composed of a polytomy among Gracilisuchidae, T. ferox plus Paracrocodylomorpha. A brief consideration of this latter clade is needed. Nesbitt (2011) considered Ticinosuchus to be a sister group of Pararocodylomorpha, a clade composed by Poposauroidea (including Qianosuchus mixtus, Poposaurus gracilis, Shuvosaurus inexpectus and their related taxa) plus Loricata (including P. chiniquensis, S. galilei, Rauisuchidae, Crocodylomorpha and related taxa). Paracrocodylomorpha is phylogenetically defined as a node-based clade composed of the least inclusive clade containing Poposaurus and Crocodylus niloticus Laurenti, 1768 (Nesbitt, 2011). In this sense, Paracrocodylomorpha is revealed in the present analysis, although it would not be accurate if Ticinosuchus belongs to this group or if it is the sister group. Likewise, it is important to consider that other phylogenetic analyses support Phytosauria as an early branch on Pseudosuchia (e.g. Brusatte et al. 2010; Ezcurra, 2016), contrasting with the analysis of Nesbitt (2011) and probably influencing the relative topology on Pseudosuchia with polarization/optimization of character states among transformational series. When constraint among Erpetosuchidae and Ornithosuchidae was forced, it resulted in 180 most parsimonious trees, with zero Bremer support. The only controversial synapomorphy for this clade is the presence of anteroposteriorly longer than wide dorsal presacral osteoderms, shared by P. candelariensis, E. granti (NHMUK R3139R) and O. woodwardia (HHMUK R2410), whereas the osteoderms of Parringtonia (NHMUK R8646) are squared, those in R. tenuisceps (PVL 3827) are wider than long, and none in V. rusconii (Bonaparte, 1972; von Baczko et al., 2014) is preserved (character 407). A previous preliminary analysis of P. candelariensis (Lacerda et al., 2016), proposed it as an early branch of Ornithosuchidae. However, this analysis did not incorporate E. granti and P. gracilis, and some character states were modified with a more accurate revision of the anatomy, as well as CT scan analysis (e.g. the relative inclination between premaxilla and maxilla is not sustainable; the number of premaxillary teeth and number and position of the maxillary ones was revealed only by means of X-ray images). The alternative position of Erpetosuchidae, as a sister group of a clade composed by Gracilisuchidae and Paracrocodylomorpha plus Ticinosuchus, also has zero Bremer support. However, the clade composed by Erpetosuchidae plus Paracrocodylomorpha is supported by two synapomophies: presence of ventromedial process on the articular (character 157), being reversed to absence on G. stipanicicorum (Romer, 1972; Butler et al., 2014) and some Poposauroidea (Nesbitt, 2011) (S. inexpectus, Effigia okeeffeae and Lotosaurus adentus); and the scapula bearing a teardrop-shaped tuber on the posterior edge for attachment of m. triceps (character 219), being reversed on P. kirkpatricki (Chatterjee, 1985; Weinbaum, 2013), Crocodylomorpha and Loricata (Nesbitt, 2011), whereas in P. candelariensis this character is placed as missing data because this bone was not preserved. The Erpetosuchidae clade displays a low support, with a Bremer value of one and Bootstrap at 64. Two synapomorphies support this clade and are found in all three members: maxillary teeth only present on the anterior region of bone (character 17), being present in only O. woodwardi (NHMUK R2409, R3143); and maxillary region ventral to the lacrimal has a mediolateral height greater than its dorsoventral length (character 21), converging with only L. adentus and E. okeeffeae. In addition, two synapomorphies support a closer relationship among E. granti and P. gracilis: absence of tooth serration (character 168); and a longitudinal bend on the dorsal presacral osteoderms (character 404), also converging with Euparkeria capensis (SAM PK5867, 6047, 6049), Gracilisuchidae (Butler et al., 2014), B. kupferzellensis (SMNS MHI 1895); Fasolasuchus tenax (PVL 3850); Rauisuchidae (BSPG AS XXV 92, 97; Chatterjee, 1985; Weinbaum, 2013) and several crocodylomorphs (Nesbitt, 2011). DISCUSSION Erpetosuchidae is formally represented by only two taxa: P. gracilis, from the Middle Triassic (Anisian) Lifua Member of the Manda Beds of Tanzania, and E. granti, from the Late Triassic (Carnian) Lossiemouth Sandstone Formation of Scotland (Fig. 9). An incomplete fragmentary skull is referred to Erpetosuchus sp. by Olsen, Sues & Norell (2000) from the Late Triassic (Norian), New Haven Formation of Connecticut, USA. The osteology of Erpetosuchidae is poorly understood, because to date there is no complete specimen described, with species based only on fragmentary materials of skull and postcranial elements, influencing the phylogenetic affinities hypothesis (Nesbitt & Butler, 2012). Although P. candelariensis is mostly represented by cranial material, it is sufficient to propose a new taxon for the Middle–Late Triassic (Late Ladinian–earliest Carnian) of southern Brazil, and the comparative osteological and phylogenetic analysis indicates a strong case for assigning it to this clade as the earlier branch taxon. Figure 9. View largeDownload slide Temporal distribution of the different geological units that bear Erpetosuchidae and Ornithosuchidae taxa and their paleogeographical location. Based on Olsen, Sues & Norell (2000), Benton & Walker (2002), Nesbitt & Butler (2012) and von Backzo & Ezcurra (2013). Temporal constraints are based on International Chronostratigraphic Chart (ICS) 2016 chart; global map modified from Nesbitt et al. (2013). Figure 9. View largeDownload slide Temporal distribution of the different geological units that bear Erpetosuchidae and Ornithosuchidae taxa and their paleogeographical location. Based on Olsen, Sues & Norell (2000), Benton & Walker (2002), Nesbitt & Butler (2012) and von Backzo & Ezcurra (2013). Temporal constraints are based on International Chronostratigraphic Chart (ICS) 2016 chart; global map modified from Nesbitt et al. (2013). In addition to this, P. candelariensis displays clear features that are characteristic of Ornithosuchidae, such as the Y-shaped ascending process of the jugal and the distinct articulation of the anterodorsal process of the maxilla with the nasals, but differs from this group by having only four premaxillary teeth, no downturned rostrum and no diastema at the premaxilla–maxilla contact. Compared with Erpetosuchidae, Ornithosuchidae is better known, being represented by three taxa: O. woodwardi (Newton, 1894; Walker, 1964; von Baczko & Ezcurra, 2013) from the Lossiemouth Sandstones Formation of Scotland (Late Carnian–earliest Norian), V. rusconii (Bonaparte, 1970; von Baczko et al., 2014) from the Ischigualasto Formation (Late Carnian–earliest Norian) and R. tenuisceps (Bonaparte, 1967; von Baczko & Desojo, 2016) from the Los Colorados Formation (Middle Norian), both from Argentina (Fig. 9). This clade has historically been considered an odd but important group in the early evolutionary history of pseudosuchians (Brinkman, 1981; Chatterjee, 1982; Cruickshank & Benton, 1985; Novas, 1989; Sereno, 1991; Parrish, 1993; von Baczko & Ezcurra, 2013), which diverges from the rest of Archosauria by the presence of an apomorphic ‘crocodile-reversed’ ankle joint (Chatterjee, 1982). Similarities between Erpetosuchidae and Ornithosuchidae were described by Huene (1939) and Nesbitt & Butler (2012), but these were mostly superficial owing to the incomplete or fragmentary preservation of the taxa and have not been explored further in the literature. Erpetosuchidae as sister taxon to Ornithosuchidae would indicate that the evolutionary history of this lineage is more complex than previously thought and considered. This mirrors what recent studies have proposed (e.g. Nesbitt et al., 2014, 2015; Ezcurra, 2016; Ezcurra & Butler, 2015; Pinheiro et al., 2016; Stocker et al., 2016), where Triassic archosauriforms display a richer evolutionary history than previously appreciated. Alternatively, the phylogenetic analysis reveals that Erpetosuchidade also has affinities with the clade Gracilisuchidae plus Paracrocodylomorpha. This closer relationship is based on the presence of a ventromedial process on the articular, and the scapula bearing a teardrop-shaped tuber on the posterior edge for the attachment of the m. triceps. However, among Erpetosuchidae taxa, both characteristics are only preserved and scored in E. granti. In this sense, these morphologies present in P. candelariensis cannot be representative of the Erpetosuchidae clade, indicating a case of morphological convergence with paracrocodylomorphs or an autapomorphic condition for this taxon. To clarify this, more information on E. granti and P. gracilis is needed, which will require new specimens. Additionally, P. candelariensis is the first member of the Erpetosuchidae described from southwestern Pangea. The chronologically older and more derived P. gracilis indicates a complex diversification history of these forms that presents many interesting questions for future work in Triassic archosauriform evolution. Furthermore, there are other factors that must be analysed, such as the role that the major biotas played in the evolution of these linages, given that P. candelariensis belonged to a highly competitive trophic web (the Dinodontosaurus Assemblage Zone) and co-habitated with some similar forms that probably shared similar habits, such as medium-sized carnivores like D. quartacolonia and the much larger P. chiniquensis. CONCLUSION The present work describes the new taxon P. candelariensis from the Middle–Late Triassic (Ladinian/Carnian) of Brazil, representing the earliest diverging branch of Erpetosuchidae. Our phylogenetic analysis reveals a modified interpretation of pseudosuchian evolution, with two possibilities for Erpetosuchidae relationships: an early branch of pseudosuchians, being a sister group of Ornithosuchidae; or a closer relationship with the clade composed by Gracilisuchidae and Paracrodylomorpha. Unfortunately, the specimen lacks most of its postcranial skeleton, preventing a more accurate comparison among pseudosuchians. On the time distribution, the new taxa from the Ladinian/Carnian age fills the temporal gap in the Erpetosuchidae clade, between P. gracilis from the Anisian and E. granti from the late Carnian–Norian. SUPPORTING INFORMATION Additional Supporting Information may be found in the online version of this article at the publisher’s website: Appendix S1. Rare earth element analysis. Appendix S2. Phylogenetic analysis. ACKNOWLEDGMENTS We would like to thank Agustin Martinelli, Bianca Mastrantonio, Bélen von Baczko, Julia Desojo, Max Langer, Martin Ezcurra and Voltaire Paes Neto for the useful discussions on Triassic archosaur evolution and diversity. We thank Felipe Pinheiro, Tomaz Melo and Marcos Sales for the discussions that helped in choosing the name of the taxon. The photographs were skillfully taken by Luiz Flávio Lopes (UFRGS). 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Triassic reptiles of the Elgin area: Ornithosuchus and the origins of carnosaurs. Philosophical Transactions of the Royal Society of London, Series B: Biological Sciences  248: 53– 164. Google Scholar CrossRef Search ADS   Walker AD. 1968. Protosuchus, Proterochampsa, and the origin of phytosaurs and crocodiles. Geological Magazine  105: 1– 14. Google Scholar CrossRef Search ADS   Walker AD. 1970. A revision of the Jurassic reptile Hallopus victor (Marsh), with remarks on the classification of crocodiles. Philosophical Transactions of the Royal Society of London Series B, Biological Sciences  257: 323– 372. Google Scholar CrossRef Search ADS   Watson DMS. 1917. A sketch-classification of the pre-Jurassic tetrapod vertebrates. Proceedings of the Zoological Society, London  1917: 167– 186. Weinbaum JC. 2011. The skull of Postosuchus kirkpatricki (Archosauria: Paracrocodyliformes) from the Upper Triassic of the United States. PaleoBios  30: 18– 44. Weinbaum JC. 2013. Postcranial skeleton of Postosuchus kirkpatricki (Archosauria; Paracrocodylomorpha) from the Upper Triassic of the United States. Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and the Kin . S. Nesbitt, J. B. Desojo and R. B. Irmis. London, Geological Society of London, Special Publications. 379: 525– 553. Wu X-C, Liu J, Li J-L. 2001. The anatomy of the first archosauriform (Diapsida) from the terrestrial Upper Triassic of China. Vertebrata Palasiatica  39: 251– 265. Wu X-C, Russell A. 2001. Redescription of Turfanosuchus dabanensis (Archosauriformes) and new information on its phylogenetic relationships. Journal of Vertebrate Paleontology  21: 40– 50. Google Scholar CrossRef Search ADS   Zittel KA. 1887–1890. Handbuch der Palaontologie , Vol. 3: Vertebrata (Pisces, Amphibia, Reptilia, Aves). Oldenbourg, Munich, 900 pp. APPENDIX Measurements of the skull (left side) and postcranial elements in MMACR-PV-036-T (in centimetres) Skull length  34.2  Skull maximal height  11.5  Premaxilla body length  5.2  Premaxilla body height  3.5  Maxilla maximal length  13.6  Maxilla maximal height  5.3  Antorbital fenestra length  4.5  Antorbital fenestra height  1.3  Nasal length  14.3  Lacrimal length  6.4  Lacrimal height (exposed in lateral view)  4.2  Frontal width  5.7  Prefrontal length  6.7  Prefrontal width  3.3  Orbit length  4.4  Orbit height  4.8  Frontal length  7.8  Supratemporal fenestra length  4.7  Supratemporal fenestra width  4.9  Quadratojugal length  10.2  Parietal maximal width  12.6  Parietal minimal width  1.2  Supraoccipital height  4.2  Supraoccipital width  11.7  Left mandible length  38  Vertebral centrum length  4.7  Vertebral centrum width  3.8  Skull length  34.2  Skull maximal height  11.5  Premaxilla body length  5.2  Premaxilla body height  3.5  Maxilla maximal length  13.6  Maxilla maximal height  5.3  Antorbital fenestra length  4.5  Antorbital fenestra height  1.3  Nasal length  14.3  Lacrimal length  6.4  Lacrimal height (exposed in lateral view)  4.2  Frontal width  5.7  Prefrontal length  6.7  Prefrontal width  3.3  Orbit length  4.4  Orbit height  4.8  Frontal length  7.8  Supratemporal fenestra length  4.7  Supratemporal fenestra width  4.9  Quadratojugal length  10.2  Parietal maximal width  12.6  Parietal minimal width  1.2  Supraoccipital height  4.2  Supraoccipital width  11.7  Left mandible length  38  Vertebral centrum length  4.7  Vertebral centrum width  3.8  View Large Skull length  34.2  Skull maximal height  11.5  Premaxilla body length  5.2  Premaxilla body height  3.5  Maxilla maximal length  13.6  Maxilla maximal height  5.3  Antorbital fenestra length  4.5  Antorbital fenestra height  1.3  Nasal length  14.3  Lacrimal length  6.4  Lacrimal height (exposed in lateral view)  4.2  Frontal width  5.7  Prefrontal length  6.7  Prefrontal width  3.3  Orbit length  4.4  Orbit height  4.8  Frontal length  7.8  Supratemporal fenestra length  4.7  Supratemporal fenestra width  4.9  Quadratojugal length  10.2  Parietal maximal width  12.6  Parietal minimal width  1.2  Supraoccipital height  4.2  Supraoccipital width  11.7  Left mandible length  38  Vertebral centrum length  4.7  Vertebral centrum width  3.8  Skull length  34.2  Skull maximal height  11.5  Premaxilla body length  5.2  Premaxilla body height  3.5  Maxilla maximal length  13.6  Maxilla maximal height  5.3  Antorbital fenestra length  4.5  Antorbital fenestra height  1.3  Nasal length  14.3  Lacrimal length  6.4  Lacrimal height (exposed in lateral view)  4.2  Frontal width  5.7  Prefrontal length  6.7  Prefrontal width  3.3  Orbit length  4.4  Orbit height  4.8  Frontal length  7.8  Supratemporal fenestra length  4.7  Supratemporal fenestra width  4.9  Quadratojugal length  10.2  Parietal maximal width  12.6  Parietal minimal width  1.2  Supraoccipital height  4.2  Supraoccipital width  11.7  Left mandible length  38  Vertebral centrum length  4.7  Vertebral centrum width  3.8  View Large © 2018 The Linnean Society of London, Zoological Journal of the Linnean Society This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Zoological Journal of the Linnean Society Oxford University Press

A new erpetosuchid (Pseudosuchia, Archosauria) from the Middle–Late Triassic of Southern Brazil

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The Linnean Society of London
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© 2018 The Linnean Society of London, Zoological Journal of the Linnean Society
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0024-4082
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Abstract

Abstract The evolution and diversification of Triassic pseudosuchian lineages has been the subject of much interest and revision in the last couple of decades, fuelled by new and important discoveries, which have allowed for better-sampled phylogenetic analysis. In the present contribution, we add to this by describing a new taxon, Pagosvenator candelariensis gen. et sp. nov., for the Middle–Late Triassic Dinodontosaurus Assemblage Zone of the Santa Maria Supersequence of southernmost Brazil. A comparative osteological analysis combined with a phylogenetic analysis supports its inclusion within the clade Erpetosuchidae and provides an insight into the phylogenetic relationship and evolutionary history of this clade, with two possibilities for the Erpetosuchidae relationship: as an early branch of pseudosuchians, being a sister group of Ornithosuchidae; or a closer relationship with the clade composed by Gracilisuchidae and Paracrodylomorpha with respect to Orntithosuchidae and Aetosauria. Additionally, the results presented and discussed here are of biostratigraphical importance, given that the taxon is from the Ladinian/Carnian age and would fill a temporal gap that exists within Erpetosuchidae between Parringtonia gracilis from the Anisian and Erpetosuchus from late the Carnian to Norian. Furthermore, it would be the first occurrence of a member of this clade in South America. Archosauria, Brazil, Erpetosuchidae, Pagosvenator, Santa Maria Supersequence, South America, Triassic INTRODUCTION Archosauria is a diverse clade composed of the crocodilians, birds and many extinct lineages (Gauthier, 1984; Gauthier & Padian, 1985; Benton & Clark, 1988; Sereno, 1991; Juul, 1994; Brusatte et al., 2010; Butler et al., 2011; Nesbitt, 2011; Ezcurra, 2016). Historically, aside from dinosaurs, there has been reduced enthusiasm over this clade and other non-archosaurian archosauriforms that also evolved in the Triassic Period; however, recent rekindled interested, sparked by new discoveries (e.g. Nesbitt et al., 2014; Ezcurra & Butler, 2015; Pinheiro et al., 2016; Stocker et al., 2016) along with revisions of previously described taxa, indicate a much richer diversity than was previously imagined (Brusatte et al., 2011). These discoveries have allowed for better-sampled matrixes and more robust cladistic analysis (Brusatte et al., 2010; Nesbitt, 2011; Butler et al., 2011; von Baczko, Desojo & Pol, 2014; Nesbitt et al., 2015; Ezcurra, 2016). Although consensus has been reached in some topologies, with historically clear monophyletic groups, such as Aetosauria (Brusatte et al., 2010; Nesbitt, 2011; Desojo et al., 2013;,Parker, 2016), others, such as the relationship of Phytosauria among archosauriforms (see discussion by Nesbitt, 2011; Ezcurra, 2016) and problematic taxa that are represented by mostly incomplete specimens display low support owing to data matrixes with ambiguous characters or a history of conflicting topologies (e.g. Gower, 2000; Brusatte et al., 2010; Nesbitt, 2011; Nesbitt & Butler, 2012; Nesbitt et al., 2013; Ezcurra, 2016). Unfortunately, even with these new insights, there are still many taxa represented by only a few or mostly incomplete specimens, and a large number of ghost lineages still haunt our view of the Triassic biotas. This is, of course, the nature of the fossil record, so there is a need for new discoveries to advance our understanding and to achieve better-supported phylogenetic analyses (Fig. 1). Figure 1. View largeDownload slide Distinct proposals of phylogenetic relationships within archosauriforms and archosaurs. A, Butler et al., (2014) based on a modified matrix of Nesbitt (2011). B, Ezcurra (2016). C, modified cladogram of Nesbitt & Butler, 2012 with the red lines and asterisks indicating the possible phylogenetic positions of Erpetosuchidae. Abbreviations: Arcf, Archosauriforms; Arch, Archosauria; Ps, Pseudosuchia. Figure 1. View largeDownload slide Distinct proposals of phylogenetic relationships within archosauriforms and archosaurs. A, Butler et al., (2014) based on a modified matrix of Nesbitt (2011). B, Ezcurra (2016). C, modified cladogram of Nesbitt & Butler, 2012 with the red lines and asterisks indicating the possible phylogenetic positions of Erpetosuchidae. Abbreviations: Arcf, Archosauriforms; Arch, Archosauria; Ps, Pseudosuchia. The Triassic outcrops of the Santa Maria Supersequence (Middle–Late Triassic) located in the central region of the Rio Grande do Sul State of southern Brazil have historically been the site of many important finds since they were first scientifically prospected in the late 1920s (Huene, 1935–1942, 1942; Beltrão, 1965). Efforts to explore these and new localities have continued during subsequent decades (Barberena, 1977; Barberena et al., 1985; Schultz, Scherer & Barberena, 2000; Da-Rosa, 2014; Horn et al., 2014; Müller et al., 2014) and have produced an ample record for many groups of archosaurs and non-archosaurian archosauriforms, such as aetosaurs (Desojo, Ezcurra & Kischlat, 2012; Da-Silva et al., 2014), doswellids (Desojo, Ezcurra & Schultz, 2011), early branch loricatans (Barberena, 1978; França, Ferigolo & Langer, 2011; Lacerda, Schultz & Bertoni-Machado, 2015; Roberto-Da-Silva et al., 2014), rauisuchids (Huene, 1935–1942; Lautenschlager & Rauhut, 2014), poposaurids (França et al., 2014), phytosaurs (Kischlat & Lucas, 2003), proterochampsids (Bertoni-Machado & Kischlat, 2003; Raugust, Lacerda & Schultz, 2013), aphanosaurians (Nesbitt et al., 2017), a possible pterosaurs (Bonaparte, Schultz & Soares, 2010; Dalla Vecchia, 2013) and several dinosauriforms (e.g. Colbert, 1970; Bonaparte, Ferigolo & Ribeiro, 1999; Langer et al., 1999; Leal et al., 2004; Ferigolo & Langer, 2006; Cabreira et al., 2011, 2016; Pinheiro, 2016). In the present contribution, we add to this record by describing a new taxon. This increases the diversity of archosaur lineages for the Triassic of this region by presenting the first occurrence of a member of the Erpetosuchidae in South America, which, in turn, gives rise to interesting questions on the paleobiogeographical distribution and evolution of this clade. Erpetosuchidae was proposed by Watson (1917) to include Erpetosuchus granti, which was described by Newton (1894) based on specimens from the Lossiemouth Sandstone Formation (late Carnian–Norian/Late Triassic), Scotland, which recognized its relationship within Archosauria, possibly closer to phytosaurs and aetosaurs, but also displaying some similarities to crocodilians (Benton & Walker, 2002). Huene (1939) described Parringtonia gracilis from the Lifua Member of the Manda Beds of Tanzania (latest Anisian/Middle Triassic) and referred it to Pseudosuchia, acknowledging some of its similarities to Ornithosuchus woodwardi Newton, 1894 (sensuvon Baczko & Ezcurra, 2016) and Saltopus elginensis (Huene, 1910), but considered the preserved material insufficient to determine whether the taxon was closely related to these taxa or if instead it represented a new pseudosuchian lineage. Similarities on the scapulae of Parringtonia and Erpetosuchus were noted by Krebs (1965), but the inclusion of both taxa in a single group was proposed in several articles by Walker (1961, 1968, 1970), with a formal diagnosis of Erpetosuchidae only provided later by Krebs (1976), which retained both taxa. The removal of Parringtonia from this group was proposed by Benton & Walker (2002), suggesting that the similarities were possible plesiomorphies. An incomplete specimen (AMNH 29300) is referred to Erpetosuchus sp. by Olsen, Sues & Norell (2000) from the Late Triassic (Norian) New Haven Formation of Connecticut, USA. Lastly, Nesbitt & Butler (2012) phylogenetically defined Erpetosuchidae as a branch-based clade that includes Parringtonia and Erpetosuchus, but displayed a poor resolution within Archosauria (Fig. 1C) In addition, Dyoplax arenaceus Fraas, 1867 (Maisch, Matzke & Rathgeber, 2013) from the Schilfsandstein Formation (early Carnian/Late Triassic) of Germany, was proposed by Walker (1961, 1968, 1970) as a member of the Erpetosuchidae. The phylogenetic position of this taxon has been greatly debated, having been considered closer to Aetosauria (Huene, 1903), Erpetosuchidae (Walker, 1961, 1968, 1970; Maisch et al., 2013) or Crocodylomorpha (Lucas, Wild & Hunt, 1998; Benton & Walker, 2002). In the analysis by Nesbitt & Butler (2012), Dyoplax was not included because these authors concluded that the taxon did not display clear erpetosuchid features, although they did not completely exclude the possibility, considering its overall morphology. However, this would require a better understanding of its osteology, which is possible only with the discovery and study of new materials. MATERIAL AND METHODS The specimen is composed of a single mostly complete but badly preserved skull with mandibles, associated with some postcranial elements (holotype MMACR PV 036-T). Most of the description and comparative osteological study is based on the structures present on the right side of the skull, which is better preserved. Measurements of the specimen are provided in Appendix section. Preparation of the specimen was undertaken using mechanical chisels and microtools at the start of its study by one of the authors (M.B.L.). However, owing to its hardened preservation, especially of the underlying rock matrix, mechanical preparation was very limited, and most of the ventral portion of the fossil remained concealed by the matrix. Computed tomography (CT) was used to view inaccessible areas, such as the palatal region, and to deduce the number of alveoli on the jaws. The specimen was scanned at the Serpal Clínica de Diagnósticos, Porto Alegre, Brazil, under a medical GE Light Speed Machine with the following settings: slice thickness of 1 mm, slice increment (interslice spacing) of 0.6 mm, field of view of 250 mm, 120 kV and 150 mA. The data were output from the scanner in DICOM format. The type locality is unknown. The specimen was donated to the Museu Municipal Aristides Carlos Rodrigues in the Municipality of Candelária (MMACR) by a local citizen who requested, emphatically, to remain anonymous and did not reveal the place of the discovery. The only information that was provided to the museum curator was that the fossil was discovered 20 years ago at the margin of one of the many artificial ponds (‘açudes’) that exist in that region. The donor collected the specimen not considering it to be a fossil but an ‘odd, skull-shaped rock’ and subsequently used it as a curiosity piece in his living room for the following two decades. Then, on Christmas Day 2013, he donated it to the local museum (MMACR). This was probably motivated by an increase in the interest on fossils and prehistoric life by the citizens of the town and neighbouring region in response to efforts by the local museum curator and staff. The preservation pattern provided a clue to its origin, at least at the biostratigraphical level, because it matched the fossil preservation of specimens from the Dinodontosaurus Assemblage Zone (Holz & Schultz, 1998), but further support was needed. A rare earth element (REE) analysis was chosen to test this inference, because this methodology has been used successfully to establish specimen origins (e.g. Lukens, Grandstaff & Terry, 2009; Suarez, Macpherson & Grandstaff, 2009). Samples were collected from the studied specimen and from an unprepared and undescribed dicynodont deposited in the collection of the Laboratório de Paleovertebrados of the Universidade Federal do Rio Grande do Sul, which was discovered in the ‘Sanga Pascual’ outcrop near the Municipality of Candelária and which has been biostratigraphically established as belonging to the Dinodontosaurus Assemblage Zone (Barberena, 1977; Schultz et al., 2000). The samples were prepared according to the standard methodology and sent to Activation Laboratories Ltd, Ancaaster, ON, Canada, where they were subjected to a UT-7 sodium peroxide fusion (ICPMS) analytical package. The results were included in a database of REE samples from fossil-bearing outcrops of major sedimentary basins in Brazil that is currently in the final stages of construction at the Setor de Geociências at the Universidade Federal do Rio Grande do Sul (UFRGS) by P. A. V. Paim and V. P. Pereira under the advisement of M. B. Soares (see Supporting Information Appendix S1). The results indicated a close match with samples of the Santa Maria Supersequence and especially of the Dinodontosaurus Assemblage Zone, but displayed a signature that did not match that of any outcrop that was included in the database, thus indicating that the fossil was not discovered in any of the more well-known sites. The full description of the methods used and the results are presented in Supporting Information Appendix S1. Institutional abbreviations BSPG, Bayerische Staatssammlung für Paläontologie und Geologie and Department of Earth and Environmental Sciences, Munich, Germany; CPEZ, Coleção de Paleontologia do Museu Paleontológico e Arqueológico Walter Ilha, São Pedro do Sul, Brazil; MCN, Museu de Ciências Naturais da Fundação Zoobotânica do Rio Grande do Sul, Porto Alegre, Brazil; MMACR, Museu Municipal Aristides Carlos Rodrigues, Candelária, Brazil; NHMUK, The Natural History Museum, London, UK; PULR, Museu de Ciencias Naturales, Univerisdade Nacional de La Rioja, La Rioja, Argentina; PVL, Paleontología de Vertebrados, Instituto ‘Miguel Lillo’, San Miguel de Tucumán, Argentina; PVSJ, División de Paleontología de Vertebrados del Museo de Ciencias Naturales y Universidad Nacional de San Juan, San Juan, Argentina; SAM, Iziko South African Museum, Cape Town, South Africa; SMNS, Staatliches Museum für Naturkunde Stuttgart, Stuttgart, Germany; UFRGS-PV, Laboratório de Paleovertebrados da Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil. SYSTEMATIC PALEONTOLOGY Archosauria Cope, 1869 sensu Gauthier & Padian (1985,) Pseudosuchia Zittel, 1887–1890 sensu Gauthier & Padian (1985,) Erpetosuchidae Watson, 1917 sensu Nesbitt & Butler (2012) Pagosvenator candelariensis gen. et sp. nov. urn:lsid:zoobank.org:act:59A6DE11-4370-4C5F-8CD9-DAF8E54C616B urn:lsid:zoobank.org:act:FE81FC65-99DC-4475-8978-0E49FE481C25 Etymology: ‘Pagos’ is a regional gaucho jargon term (sometimes used in the singular, pago, but its plural use is more common) that is derived from the Latin ‘pagus’, meaning ‘countryside’ or ‘rural community’; ‘venator’ is Latin for ‘hunter’ owing to it being a relatively large carnivore; and ‘candelariensis’ is with regard to the city of Candelária, where the museum in which the specimen is deposited is located. The name means ‘the hunter from the surroundings of Candelária’. Holotype: MMACR PV 036-T; mostly complete and articulated skull and lower jaws, associated with two incomplete vertebrae and five heavily ornamented osteoderms. Diagnosis: Pseudosuchian (Erpetosuchidae) archosaur, with the following unique combination of characters states: four premaxillary teeth; maxilla with an edentulous posterior half, large and posteriorly deep antorbital fossa and a posteriorly positioned antorbital fenestra relative to the anteroposterior length of the rostrum; ascending process of the jugal bifurcates dorsally into a V-shaped structure that composes the ventral margin of the orbit; lacrimals do not contribute to the skull roof; palpebral bones; slightly longer than wide osteoderms with heavily ornamented dorsal surfaces, displaying small pits and short ridges. Type locality and age: The locality is unknown (see the previous section and the Supporting Information Appendix S1). The type of preservation of the specimen with a supporting REE analysis indicates that it belongs to a site from the Dinodontosaurus Assemblage Zone, Middle-Late Triassic (late Ladinian–earliest Carnian age), whose outcrops are placed south of the city of Candelária. Description Skull overview The skull of P. candelariensis suffered taphonomic alterations, with the majority of the elements that form the infratemporal fenestra being altered, in the case of the left side, or lost, in the case of the right side (Fig. 2). The anterior part of the rostrum was damaged and rotated 15° clockwise. The right side of the skull displays major distortions, with many elements, specifically the ones that form the ventral margin of the maxilla, the posteroventral border of the orbit and the infratemporal fenestra, being displaced or lost. Some suture patterns are also distorted, which results in some paired elements not displaying mirrored features. Figure 2. View largeDownload slide A–H, images generated by computer tomography of MMACR PV 036-T, presenting the different portions of the specimen and some of the preservational alterations that the specimen suffered: dorsal (A, B), ventral (C, D), left lateral (E, F) and right lateral (G, H) views. Colorized models are not to scale. Figure 2. View largeDownload slide A–H, images generated by computer tomography of MMACR PV 036-T, presenting the different portions of the specimen and some of the preservational alterations that the specimen suffered: dorsal (A, B), ventral (C, D), left lateral (E, F) and right lateral (G, H) views. Colorized models are not to scale. The premaxilla is formed by a subquadrangular main body, a gracile anterodorsal process and a narrow posterodorsal process. Although both premaxillae are morphologically similar, the right one is distorted and dorsoventrally shorter owing to a heightened ventral curvature. In lateral view, the anterior margin of the main body is sub-vertical, with an anteroventral margin that is recurved up to the remains of the first premaxillary tooth (Fig. 3). This margin displays a small posterodorsal curvature that ends at the base of the anterodorsal process, which was initially interpreted by Lacerda, França & Schultz (2016) as similar to the condition found in Ornithosuchidae. This posteroventral curvature was extended dorsally because of the compression of the anterior portion of the rostrum, which artificially created an ornithosuchid-like ‘downturned’ condition. The dorsal third of the body of the premaxillae is more medially compressed, forming a marked fossa that forms the anteroventral border of the external naris. Figure 3. View largeDownload slide A, B, photograph (A) and interpretive illustration (B) of specimen MMACR PV 036-T in left lateral view. Abbreviations: AFO, antorbital fossa; AN, angular; AOF, antorbital fenestra; AR, articular; AV, alveoli; F, frontal; FPMX, premaxillary fossa; J, jugal; LA, lacrimal; MSH, mandibular shelf; N, nasal; OR, orbit; PA, parietal; PAL, palpebral; PF, prefrontal; PMX, premaxilla; PO, postorbital; QJ, quadratojugal; SQ, squamosal; SU, surangular; T, teeth; ?, unidentified bone fragments. Concretions are in dark grey, cranial openings in black, and broken areas are crosshatched. Figure 3. View largeDownload slide A, B, photograph (A) and interpretive illustration (B) of specimen MMACR PV 036-T in left lateral view. Abbreviations: AFO, antorbital fossa; AN, angular; AOF, antorbital fenestra; AR, articular; AV, alveoli; F, frontal; FPMX, premaxillary fossa; J, jugal; LA, lacrimal; MSH, mandibular shelf; N, nasal; OR, orbit; PA, parietal; PAL, palpebral; PF, prefrontal; PMX, premaxilla; PO, postorbital; QJ, quadratojugal; SQ, squamosal; SU, surangular; T, teeth; ?, unidentified bone fragments. Concretions are in dark grey, cranial openings in black, and broken areas are crosshatched. The anterodorsal process is narrow and articulates posterodorsally between two anteroventral projections of the nasals in a V-shaped contact (Fig. 3), similar to the one described in O. woodwardi (Walker, 1964) and Riojasuchus tenuisceps (PVL 3827; Bonaparte, 1967; von Bazcko & Desojo, 2016). This area is ventrodorsally compressed, which has altered its dimensions and most of the dorsal border of the naris, which is slightly reduced in height but not overall form. The posterodorsal process of the premaxilla has a wide base that tapers posteriorly, with its most posterior end articulating between two ventral processes of the nasal and ending posterior to the nasal opening. This process is greater than the anteroposterior length of the main body of premaxilla, similar to Gracilisuchidae and early branch loricatans and different from the comparatively smaller process in E. granti (NHMUK R3139), Ornithosuchidae (NHMUK PV R3143; PVL 3827) and Aetosauria (e.g. SMNS 5770) (Nesbitt, 2011; Nesbitt & Butler, 2012). The posterodorsal process is better observed in dorsal view, because in lateral view, owing to the above- mentioned alteration of this region of the skull, it appears as a smaller, acute process. Its distal end fits into a slot in the nasal, similar to Revueltosaurus callenderi (Hunt, 1989; Parker et al., 2005) and Gracilisuchidae (Butler et al., 2014). Tooth remains are preserved on the anterolateral and ventral portions of the rostrum, but only the two on the left premaxilla are preserved in their sockets, with the most posterior one being the better preserved. The above-mentioned alteration in the ventral curvature damaged most of the area, and its remains were preserved in a large concretion mixed with bone and tooth fragments that obscures most of this area. The number of alveoli was determined only by CT scans, which revealed four in each premaxilla (Fig. 4). The number of premaxillary teeth is variable in pseudosuchians. Four teeth are in E. granti (NHMUK R3139), Aetosaurus ferratus (SMNS 5770; Schoch, 2007), Gracilisuchus stipanicicorum Romer, 1972 (Butler et al., 2014) and early branch taxa of Loricata, whereas some taxa, such as Stagonolepis robertsoni Agassiz, 1844, Revueltosaurus callenderi, Turfanosuchus dabanensis Wu, Lui & Li, 2001 and Yonghesuchus sangbiensis Wu & Russell, 2001 bear five teeth, and O. woodwardi and R. tenuisceps have three teeth in the premaxilla (Walker, 1961, Nesbitt, 2011; Nesbitt & Butler, 2012). Figure 4. View largeDownload slide A, B, detail photograph (A) and interpretative drawing (B) of the rostral region of MMACR PV 036-T in ventral view. Arrows indicate the fracture points of the anterior tips of the mandibles. C, computed tomography capture of the same region, in ventral view, indicating the number of alveoli on the premaxilla and the first maxillary tooth immediately after the premaxilla–maxilla contact. Abbreviations: L mand, left mandible; MX, maxilla; PMX, premaxilla; R mand, right mandible; t, teeth; I–IV, premaxillary teeth; I(mx), first maxillary tooth; pmx/mx, contact between the premaxilla and maxilla. Concretions are in dark grey, and broken areas are crosshatched. Figure 4. View largeDownload slide A, B, detail photograph (A) and interpretative drawing (B) of the rostral region of MMACR PV 036-T in ventral view. Arrows indicate the fracture points of the anterior tips of the mandibles. C, computed tomography capture of the same region, in ventral view, indicating the number of alveoli on the premaxilla and the first maxillary tooth immediately after the premaxilla–maxilla contact. Abbreviations: L mand, left mandible; MX, maxilla; PMX, premaxilla; R mand, right mandible; t, teeth; I–IV, premaxillary teeth; I(mx), first maxillary tooth; pmx/mx, contact between the premaxilla and maxilla. Concretions are in dark grey, and broken areas are crosshatched. The maxilla is divided in a subrectangular main body and a dorsoventrally tall and anteroposteriorly wide ascending process. The anterior portion, which articulates with the premaxilla, in dorsal view has a marked transverse expansion, which is mirrored in both maxillae, a condition that is uncommon in archosaurs but is described in P. gracilis (NHMUK R8646; Nesbitt & Butler, 2012). In lateral view, the main body is dorsoventrally expanded, and both anterior and posterior areas display similar dorsoventral depths. The premaxilla–maxilla suture is tightly closed, not displaying any foramina or accessory openings, and not displaying a diastema between the elements, unlike Ornithosuchidae (NHMUK PV R3143; PVL 3827). The anterior margin is rounded, slopping posterodorsally into the anteroposteriorly elongated ascending process. This process articulates posteriorly between the nasal and posteroventrally with the anterodorsal and anterior margins of the lacrimal. The posterior portion forms the majority of the anterior margin of the antorbital fenestra. The anterior portion of the ventral margin is straight, up to the area where the rostrum is damaged. From there, it is slightly concave, and the ventral area with the alveoli is more laterally projected. This projection was probably caused by taphonomic compression. On the posterior end of this margin, there is a small posteroventral process that extends 8 mm beyond the articulation with the jugal. The posterior process of the maxilla has almost the same dorsoventral height on the posterior region, not tapering as in Ornithosuchidae (NHMUK PV R3143; PVL 3827) or expanding as in E. granti (NHMUK R3139) and P. gracilis (NHMUK PV R8646) (Nesbitt & Butler, 2012). However, the mediolateral length is greater than the dorsoventral height on the level of the main body of the lacrimal, a characteristic shared with E. granti and P. gracilis (Nesbitt & Butler, 2012). The antorbital fossa occupies most of the lateral surface of the maxilla. This fossa gradually deepens posteriorly, reaching its deepest point close to the ventral area of the lacrimal and the anterior margin of the jugal. The antorbital fenestra is half the anteroposterior length of the fossa and is posteriorly located on the rostrum. It is subtriangular but very dorsoventrally compressed, almost to the point of a slit, with a rounded anterior tip, and displays a 25° dorsoventral inclination with regard to the central axis of the maxilla. The nearly pointed anterior margin of the antorbital fenestra is shared with Erpetosuchus and some ornithosuchid taxa (Venaticosuchus rusconi and R. tenuisceps), but a gently rounded anterior margin is observed in O. woodwardi (Nesbitt & Butler, 2012; von Baczko et al., 2014; von Baczko & Desojo, 2016; von Baczko & Ezcurra, 2016). Owing to the lateral distortion of the ventral margin of the left maxilla, the posterior third of this element is turned laterally, exposing the ventral margin, with five concretion-filled alveoli and an edentulous posterior region after the last alveolus. Computer imaging identified teeth starting immediately posterior to the articulation with the premaxilla, so at least six maxillary teeth would be present. With the exception of archosaurs that have a more specialized maxilla for herbivory (e.g. poposaurids), an edentulous posterior region of the maxilla is described only in Erpetosuchidae (Nesbitt, 2011; Nesbitt & Butler, 2012). However, this would differ from P. gracilis, which has only five, and E. granti, which has four, but is similar to the possible nine maxillary teeth inferred for a specimen attributed to Erpetosuchus sp. (AMNH 29300; Olsen, Sues & Norell, 2000). All teeth are badly preserved, being incomplete or covered in a thick layer of concretion. The two largest teeth are on the ventral border of the right maxilla, and three disarticulated teeth are preserved along the underlying lateral face of the left mandible. The teeth are anteroposteriorly recurved and lateromedially compressed, and there is no indication of any serrations (Fig. 3). The nasals are anteroposteriorly elongated elements that form the majority of the anterodorsal and dorsolateral surface of the rostrum, with both elements articulating medially. The dorsal surface is smooth and continues the length of the skull roof, with no indication of a convexity or ‘roman nose’-like feature as in Decuriasuchus quartacolonia (MCN PV10.105a; França et al., 2011; França, Langer & Ferigolo, 2013). The anterior portion, in lateral view, is anteroventrally curved and divided into two processes. The anteroventral process forms the majority of the dorsal and posterodorsal border of the external naris and contacts the dorsal tip of the anterodorsal process of the premaxilla, and it extends laterally and anteroventrally up to half its length. The posteroventral process is comparatively short and narrow. It articulates with the posterodorsal process of the premaxilla, forming a depressed area for this contact, with a piece of the process occupying an area between the premaxilla and maxilla. The main body of the nasal forms the anterior portion of the skull roof, with a broad mediolateral length, whereas the posterior process is located on its medial half and posteriorly tapering along the articulation with the frontal. The nasal has a broad contact with the prefrontal, on the posterior margin of the main body and the anterolateral region of the posterior process, unlike in Ornithosuchidae, where these bones do not meet (Walker, 1964; von Baczko & Ezcurra, 2013; von Bazcko & Desojo, 2016). In addition, Pagosvenator does not share with the Gracilisuchidae and some loricatans (e.g. Rauisuchidae) the nasal contribution to the antorbital fossa (Nesbitt, 2011; França et al., 2013; Butler et al., 2014). The lacrimal is divided into two processes; an anterior L-shaped process that is anteroposteriorly inclined, and a posteroventral process that forms three-quarters of the anterior margin of the orbit (Fig. 3). This bone is completely covered dorsally, lacking any contribution to the skull roof. The anterior process delimits the posterior half of the dorsal and all the posterodorsal margins of the antorbital fossa, along with the posterodorsal margin of the antorbital fenestra. It forms, with the prefrontal and the jugal, a thick anterolateral expansion or ridge along the extent of the antorbital bar. This ridge forms a deep pocket on the posterodorsal end of the fossa, similar to the one in R. tenuisceps, some theropods and basal saurischians (Nesbitt, 2011; von Bazcko & Desojo, 2016 but it displays a more lateral expression, although this may have been artificially deepened as a result of the distortion already described. The prefrontal is a wide element of the skull roof, with a discrete presence on the lateral view (Figs 2, 3). It articulates anteromedially with the nasals, posteromedially with the frontal and ventromedially with the jugal, forming most of the anterior border of the orbit. Its anterior portion is not in articulation with the rostrum anteriorly, owing to the distortion that this part of the skull suffered, which is indicated by a transverse fracture on the anterior portion of both prefrontals, but would indicate the overall aspect of the anterior margins. In dorsal view, it is subrectangular, with a straight anterior margin, a convex posterior margin and a small lateral process that covers the lacrimal ventrolaterally. The dorsal surface displays a deep fossa that is mirrored on both elements. This fossa is lateral to the anterior processes of the frontal and is near an area that displays a large number of fossae and ridges that appear not to be formed by taphonomic alterations, which would indicate a heavily ornamented region of the skull roof. The lateroventral process, along with the posterodorsal region of the lacrimal, forms a bar that delimits posterodorsally the deepest part of the antorbital fossa. The frontal is a wide, dorsoventrally compressed element that articulates anteriorly with the nasals by two narrowing anterior processes, anterolaterally with the prefrontal along a sinuous contact, posterolaterally with the postorbital and posteriorly with the parietal along a lateromedially wide U-shaped process (Fig. 3). In anterior view, the lateral portion near the orbits displays a marked dorsal curvature, and its surface is marked by deep pits and ridges that are mirrored on both sides of the element and continue up to the palpebrals. The frontal makes up the dorsal border of the orbit and articulates lateroposteriorly with a palpebral element, which is better observed on its right side. The presence of a single frontal and the rare pattern of the nasal–frontal suture in archosaurs matches the condition described for E. granti (Benton & Walker, 2002), but in P. candelariensis this region of the skull roof is more lateromedially wide, whereas in the former it is more constrained. No longitudinal ridge along the midline or the anterior portion tapering anteriorly is observed in P. candelariensis, differing from Gracilisuchidae and some early branch loricatans in that these features are present (Nesbitt, 2011; Nesbitt & Butler, 2012). The right palpebral is mostly preserved, with the left one represented only by its medial portion that is still in articulation with the other elements on the dorsal margin of the orbit along a large fracture. Most of this damaged area corresponds to that which is occupied on the left side by the other palpebral and the dorsal portion of the postorbital. Additionally, the palpebral articulates posteromedially with the postfrontal and posteriorly with the postorbital. In dorsal view (Fig. 3), its shape is subrectangular, with a thick and rugose lateral margin, whereas the dorsal surface displays a series of pits and the lateral continuation of some ridges that arise on the frontal. The presence of a palpebral element is described in aetosaurs, loricatans, poposaurids, crocodylomorphs and ornithischians, with its overall morphology varying greatly between different groups, within the same taxon and during ontogeny (Nesbitt, Turner & Weinbaum, 2013b) but the palpebrals of the described specimen appear distinct, because no sub-rectangular element, in dorsal view, with shallow pits has been described. The postfrontal, in dorsal view, is an irregular bone that articulates anterolaterally with the palpebral, anteriorly and anteromedially with the frontal, posteromedially with the parietal and posterolaterally with the postorbital. As such, it does not participate in the margin of the orbits, but its convex posterior margin forms most of the anterior border of the supratemporal fenestra. Its overall irregular form, in dorsal aspect, differs from that of most of the postfrontals described in basal suchians, but its participation in the skull roof, with its posterior border forming the anterior margin of the supratemporal fenestra region, is similar to the ones in Riojasuchus (PVL 3827; von Baczko & Desojo, 2016). The left postorbital is mostly preserved and divided into an incomplete dorsal portion and a ventral portion, whereas the right postorbital is represented by only a fragment of the anterior portion. In dorsal view, it is anteroposteriorlly elongated, with its anterior region being mediolaterally expanded with a short mediolateral process. This anterior region articulates with the lateral margin of the postfrontal, and its main body forms the lateral margin of the supratemporal fenestra, which ends in a narrow posterior process that is turned lateromedially up until its broken tip. The anterior contact of the ventral portion articulates along the damaged area of the palpebral, whereas its main body projects anteroventrally and forms the posterodorsal and posterior border of the orbit. The posterior process that contacts the squamosal is mostly restricted dorsally, unlike aetosaurs, Gracilisuchus and Yonghesuchus, where it is ventrally broad. The ventral process of the postorbital in Pagosvenator is similar in length to the jugal in the composition of the postorbital bar. Only the left squamosal is preserved, and it is divided into two segments (Figs 2, 3). The first is anteriorly displaced and is ventrally displaced to the dorsal portion of the postorbital. It displays an anteroposteriorly wide dorsal section that has on its anterodorsal surface a shallow fossa for the articulation of the posterior portion of the postorbital and an anteroposteriorly curved ventral process that contacts the postorbital ramus of the ascending process of the jugal, near the articulation of this element with the ventral process of the postorbital. Owing to the damage suffered by the posterior region of the skull, it is twisted 30° anticlockwise and displaced more anteriorly, between the anterior and posterior ramus of the posterior process of the jugal. As a result of this distortion, it occupies an area equivalent to the infratemporal and exposes only two small lateral openings. The second piece is a small fragment of the posteromedial region that is positioned more posteriorly and is in articulation with the paraoccipital process of the braincase. The dorsal surface of the squamosal on the supratemporal fenestrae is smooth, without any ridges or marked edges. The ventral process lacks the lateral ridge or the anteroventral projection found in some loricatans, such as Saurosuchus galilei (PVSJ 32; Alcober, 2000) and Prestosuchus chiniquensis (UFRGS-PV-0156-T; Barberena, 1978; Azevedo, 1991). The parietal is a single element, with no indication of a parasagittal suture, similar to the condition of the frontal (Fig. 5). In dorsal view, its main body is subrectangular and dorsoventrally flat, with an anterior portion formed by two anterolateral processes that form, anteriorly, a sub-circular contact with the frontal and articulate anterolaterally with the postfrontals. Two elongated, anterolaterally compressed, posterolateral processes are present, projecting from the posterior half of the main body, and form occipital flanges, similar to O. woodwardi (NHUMK R2409; Walker, 1964). However, this process is nearly vertical, whereas in Ornithosuchidae and aetosaurs this process is > 45° inclined anteriorly. The left one is preserved, but the right has been damaged, preserving only the fragments closer to the contact with the occipital. The presence of a single parietal is uncommon in archosauriforms, being described in Erpetosuchus and in some crocodylomorphs. However, as observed in the modern taxa of the latter group, the parietal can arise as two separate elements and fuse during late ontogeny (Rieppel, 1993), although it is impossible to infer whether this was the case in the present specimen. The jugal is a triradiated element, divided into a main body, with anterior, dorsal and posterior processes. The posterior process is broken into two segments owinng to the collapse of the area of the infratemporal fenestra and disarray of the quadratojugal–jugal articulation. The anterior process is anteroposteriorly short and articulates with the main body of the maxilla, forming the posterior rim of the antorbital fossa and the posterior margin of the antorbital fenestra, a condition that is also described in Proterosuchus fergusi, some proterochampsids, phytosaurs, ornithosuchids, sauropodomorphs and ornithischians (Nesbitt, 2011; von Baczko & Desojo, 2016; Ezcurra, 2016). However, the closest match is the one described in Erpetosuchus (Benton & Walker, 2002), which displays a jugal with five processes, but with its two anterior processes forming a posterior limit to a deep antorbital fossa, which is morphologically the closest to the one in Pagosvenator. The dorsal process is divided into preorbital and postorbital rami, which form the ventral margin of the orbit and have a distinct V-shaped aspect in lateral view, like the one described in Erpetosuchus (Benton & Walker, 2002) and in ornithosuchids, but is ventrally more rounded like the one in the Riojasuchus, compared with the more acute one in Ornithosuchus (von Baczko & Desojo, 2016). The preorbital ramus articulates with the lacrimal along a broad vertical suture, whereas the postorbital ramus contacts the postorbital bone. A large area of damage is present on the lateral portion of the main body and on most of the posterior process. A longitudinal ridge is present on the lateral surface of main body of the jugal in Pagosvenator, although it does not display a bulbous appearance, such as those in rauisuchids (e.g. Gower, 1999; Lautenschlager & Rauhut, 2014). The posterior process is broken into two segments; its anterior part is wedge shaped in lateral view and positioned more posteroventrally, whereas the posterior portion is preserved in articulation with the quadratojugal on the dorsal margin of the mandible. This articulation is similar to the one in Riojasuchus and Ornithosuchus (Walker, 1964; von Bazcko & Desojo, 2016), but taphonomic alterations have twisted this area dorsolaterally, displaying the ventral area where the quadratojugal articulates with the jugal along a wide, rounded contact. The posterior process is dorsal to the quadratojugal on this contact, with posterior limits anterior to the posterior margin of lower temporal fenestra, unlike Erpetosuchus, Gracilisuchus and Yonghesuchus in that the process is located posterior to the fenestra. The elements of the posterolateral regions of the skull have suffered major displacement, whereas most of the elements of the right side have been lost. The quadratojugal is represented by only the posterior portion of the left element, with only its posterior half visible owing to the swivel of the ventral bar of the infratemporal fenestra. In dorsal view, it is an anteroposteriorly wide, subrectangular bone, with a sinuous lateral margin and a mediolaterally broad posterior region, which has a small fracture on its lateral margin. In lateral view, it articulates with the posterior process of the jugal along an anteriorly directing V-shaped suture and medially with the posterior region of the quadrate. Despite the taphonomic bias, the quadratojugal is not dorsally expanded, occupying < 80% of the posterior border of the lower temporal fenestra, unlike Erpetosuchus, Gracilisuchidae and aetosaurs. The quadrate is an anteroposteriorly elongated bone which, owing to the disarticulation of the posterior elements of the skull, is more anteriorly located, where its anterior portion is positioned lateral to the braincase and twisted dorsally (Fig. 3). It articulates laterally with the quadratojugal, with a small foramen between the two elements in its central portion. Its posterior tip is mediolaterally expanded along a straight margin of the articular condyle. The right lateral and ventral portion of the occipital region is covered by concretions and osteoderm fragments, also obscuring most elements of this side of the skull and completely covering the foramen magnum (Fig. 6). The supraoccipital, in posterior view, is a dorsoventrally short but lateromedially wide subtriangular element. It articulates dorsally with the parietal along its posterolateral processes, ventrolaterally with the opisthotic and ventrally with the exoccipitals. The dorsal surface of its main body is smooth, with no indication of a ridge or process. Only the proximal portion of the opisthotic is preserved, with a reduced posterolaterally projecting paraoccipital process that ends on a fragment of a medial portion of the squamosal. Owing to an accumulation of osteoderms on the right side of the ventral portion of the supraoccipital, only the left exoccipital is visible. It is a small, quadrangular element in posterior view, which is tightly fused anteriorly with the supraoccipital and anterolaterally with the opisthotic. Mandibles Both mandibles are present but not in articulation with the skull, being positioned under and roughly inside the mouth cavity. This placement made it impossible to visualize the tooth-bearing dorsal margin of the mandibles, and CT scans proved unreliable to provide useful information. The anterior tips of the mandibles were fractured along with the rest of the rostrum and also dislocated, with the right piece being displaced more medially and the left one more laterally, covering the region posterior to where the fracture occurred (Fig. 4). The left mandible is twisted, with its lateral face placed dorsolaterally, whereas only the ventral portion of the right mandible is visible outside the mouth cavity. Owing to these alterations, all of the medial regions of the mandibles, with the exception of the posteriormost region of the left one, are impossible to observe. Although mostly covered by the skull and distorted, the presence of a mandibular fenestra is not clear, but this is because the posterior portion of the left mandible is covered by the jugal and associated unidentified bone fragments, although the shape of mandibular bones (posterior end of dentary; anterior end of surangular and angular) indicate its presence, but its exact appearance and dimensions are impossible to establish. The dorsoventral height of the dentary is unknown owing to the obstruction of the dorsal margin. Its visible surface, ventral to the posterior area of the maxilla, indicates a dorsoventrally expanded and anteroposteriorly elongated element, which is dorsoventrally reduced anteriorly with a smooth, rounded ventral margin of the anterior tip of the mandible. Its posterodorsal margin has a short dorsal process that meets a concretion that is also at the ventral base of the squamosal, posterolaterally with the surangular and posteroventrally with the angular. The surangular is a mediolaterally compressed element that displays a dorsoventrally short anterior portion that expands posteriorly up to two-thirds of its length. It extends posteriorly, forming the majority of the posterior portion of the mandible, and almost completely excludes the articular in lateral view. This condition where the surangular completely obscures the articular laterally is similar to the one described in the loricatan Batrachotomus kupferzellensis (Gower, 1999), the paracrocodylomorph Postosuchus kirkpatricki (Weinbaum, 2011) and in Erpetosuchus (Benton & Walker, 2002), but in the latter taxon this must be considered with reservations because it is inferred based on casts that might not preserve more delicate sutures. It displays a sharp lateral shelf formeds along the anteroposterior length of its dorsal surface, with an underlaying fossa that runs ventral to the shelf. In dorsal view, the articular is a triangular element that articulates laterally with the surangular, which excludes it almost entirely from the lateral portion of the hemimandible. Its anterior portion presents an anteroposteriorly wide, concave glenoid fossa, which is covered in a thick concretion, but lacks any transverse ridge, aside from a small dorsal projection on the end of its medial portion. The medial process is present and robust, but does not present any foramen as in the Batrachotomus and Decuriasuchus (Gower, 1999; França et al., 2013). The retroarticular region displays an angled posterior process, with a longitudinal ridge that extends the posterior margin of this element dorsoventrally. Owing to the preservation of the medial portion of the mandible, it is impossible to interpret the form and sutures of the prearticular and coronoid bones. A number of unidentified fragments are observed on the left side of skull. The most anterior one is elongated, narrow and is positioned on the posterior region of the dentary. The second one covers the lateral side of angular, with a semicircular posterior region and a broken anterior facet. Considering the anatomical position, both bones could be skull fragments, but their poor preservation prevents a clear identification. Postcranial elements The remains of two articulated vertebrae lying on their right sides were preserved behind the occipital region of the skull (Fig. 5). One vertebra is represented only by its neural spine and left postzygapophysis, whereas the second has a complete sub-rectangular vertebral body and ventral portion of the neural arch, with the left prezygapophysis in articulation with the corresponding postzygapophysis of the adjacent preserved vertebra. Figure 5. View largeDownload slide A, B, photograph (A) and interpretive drawing (B) of MMACR PV 036-T in dorsal view. Abbreviations: AR, articular; AFO, antorbital fossa; CEN, centrum; EX, exoccipital; FO, quadratojugal–quadrate foramen; FPMX, premaxillary fossa; FR, frontal; J, jugal; MX, maxilla; N, nasal; NS, neural spine; OP, opisthotic; OR, orbit; OST, osteoderm; PA, parietal; PAL, palpebral; PF, prefrontal; PMX, premaxilla; PO, postorbital; POF, postfrontal; POZY, postzygapophysis;. PRZY, prezygapophysis; Q, quadrate; QJ, quadratojugal; SO; supraoccipital; SQ, squamosal; UTF, upper temporal fenestra. Concretions are in dark grey, cranial openings in black, and broken areas are crosshatched. Figure 5. View largeDownload slide A, B, photograph (A) and interpretive drawing (B) of MMACR PV 036-T in dorsal view. Abbreviations: AR, articular; AFO, antorbital fossa; CEN, centrum; EX, exoccipital; FO, quadratojugal–quadrate foramen; FPMX, premaxillary fossa; FR, frontal; J, jugal; MX, maxilla; N, nasal; NS, neural spine; OP, opisthotic; OR, orbit; OST, osteoderm; PA, parietal; PAL, palpebral; PF, prefrontal; PMX, premaxilla; PO, postorbital; POF, postfrontal; POZY, postzygapophysis;. PRZY, prezygapophysis; Q, quadrate; QJ, quadratojugal; SO; supraoccipital; SQ, squamosal; UTF, upper temporal fenestra. Concretions are in dark grey, cranial openings in black, and broken areas are crosshatched. Six osteoderms are associated with the specimen (Figs 5, 6). Two are complete and four incomplete, with the largest and best-preserved one being rectangular (32 mm anteroposterior length and 33 mm lateromedial width). The borders are smooth, lacking an anterior process similar to the ones in aetosaurs (Nesbitt & Butler, 2012; Desojo et al., 2013) and the doswellidae Archeopelta arborensis (CPEZ-239a; Desojo et al., 2011) (Fig. 7). All osteoderms are heavily ornamented, with a dorsal surface covered with small pits and short ridges, but lacking a central anteroposteriorly extended ridge like the one in Erpetosuchus and Parringtonia (Nesbitt & Butler, 2012). Owing to the disarticulated condition of the postcranial elements, it is unclear how the osteoderms where arranged when in articulation and which section of the cervical sequence they would belong to, even though they were preserved near the skull. However, the lengths of the osteoderms are consistent with two anteroposterior segments per vertebra, probably with a paired sagittal axis. Figure 6. View largeDownload slide A, B, photograph (A) and interpretive drawing (B) of the occipital region in posterior view. Vertebral elements were removed to detail this region more clearly. Abbreviations: EX, exoccipital; FR, frontal; OP, opisthotic; OST, osteoderms; PA, parietal; PAL, palpebral; PO, postorbital; SQ, squamosal; VERT, vertebra (portions). Concretions are in dark grey, in broken areas are crosshatched. Figure 6. View largeDownload slide A, B, photograph (A) and interpretive drawing (B) of the occipital region in posterior view. Vertebral elements were removed to detail this region more clearly. Abbreviations: EX, exoccipital; FR, frontal; OP, opisthotic; OST, osteoderms; PA, parietal; PAL, palpebral; PO, postorbital; SQ, squamosal; VERT, vertebra (portions). Concretions are in dark grey, in broken areas are crosshatched. Figure 7. View largeDownload slide A, B, photographs of the best-preserved osteoderm in MMACR PV 036-T: A, in detail; and B, isolated and with heightened shadows to display the ornamentation cover better. C–F, interpretative illustrations of various ornamented osteoderms of archosauriforms for comparison: C, osteoderm of Pagosvenator candelariensis (MMACR PV 036-T); D, osteoderm of Parringtonia gracilis in dorsal view (NHMUK R3139, redrawn based on Nesbitt & Butler, 2012); E, osteoderm of Archeopelta arborensis (CPEZ-239a; redrawn based on Desojo et al., 2012); and F, osteoderm of Tarjadia ruthae (PULR 063; redrawn based on Arcucci & Marsicano, 1998). Abbreviations: AAF, anterior articular facet; CRI, central ridge; P, pit; RI, ridge. Osteoderms are not to scale. Figure 7. View largeDownload slide A, B, photographs of the best-preserved osteoderm in MMACR PV 036-T: A, in detail; and B, isolated and with heightened shadows to display the ornamentation cover better. C–F, interpretative illustrations of various ornamented osteoderms of archosauriforms for comparison: C, osteoderm of Pagosvenator candelariensis (MMACR PV 036-T); D, osteoderm of Parringtonia gracilis in dorsal view (NHMUK R3139, redrawn based on Nesbitt & Butler, 2012); E, osteoderm of Archeopelta arborensis (CPEZ-239a; redrawn based on Desojo et al., 2012); and F, osteoderm of Tarjadia ruthae (PULR 063; redrawn based on Arcucci & Marsicano, 1998). Abbreviations: AAF, anterior articular facet; CRI, central ridge; P, pit; RI, ridge. Osteoderms are not to scale. Phylogenetic Analysis The new taxon, P. candelariensis, was included in a matrix with 418 characters and 85 terminal taxa. The matrix is based on the original analysis of Nesbitt (2011), with compilations of its modified versions by Butler et al. (2011), Nesbitt & Butler (2012), Butler et al. (2014) and von Baczcko et al. (2014). Additionally, one new character is proposed, and some characters states were altered, using information based on personal study of specimens and on recently articles (full details in the Supporting Information, Appendix S2). The matrix was analysed in TNT (Goloboff, Farris & Nixon, 2008), using a heuristic search with 10000 replicates of Wagner trees, tree bisection and reconnection (TBR) branch swapping (holding 10 trees per replicate), with collapsed branch with zero length. Some multistate characters were ordered according to parameters stated in the original analysis and above-mentioned works: 32, 52, 121, 137, 139, 156, 168, 188, 223, 247, 258, 269, 271, 291, 297, 328, 356, 377, 399, 198, 416. Bootstrap and Bremer support were calculated with scripts on TNT. Additional analyses in searching for unstable taxa were conducted in TNT, using the IterPCR script proposed by Pol & Escapa (2009). The cladistic analysis resulted in 360 most parsimonious trees, with 1358 steps. Pagosvenator candelariensis was found to be a sister group of E. granti plus P. gracilis, composing the earliest diverging branch of Erpetosuchidae (Fig. 8). Figure 8. View largeDownload slide Alternative positions of Erpetosuchidae among the relationships of Pseudosuchia, indicating a simplified version of the strict consensus trees, 360 most parsimonious trees with 1358 steps, using a phylogenetic matrix composed of 84 terminal taxa and 417 (418 above) characters. Figure 8. View largeDownload slide Alternative positions of Erpetosuchidae among the relationships of Pseudosuchia, indicating a simplified version of the strict consensus trees, 360 most parsimonious trees with 1358 steps, using a phylogenetic matrix composed of 84 terminal taxa and 417 (418 above) characters. In previous analyses, this group had been considered as an unstable taxa (Nesbitt & Butler, 2012), with six possible positions: (1) earliest branch from Pseudosuchia; (2) earliest branch from Suchia (including G. stipanicicorum, T. dabanensis, Aetosauria, Paracrocodylomorpha and other related taxa); (3) sister group of T. dabanensis (not found as sister group of G. stipanicicorum in this analysis); (4) earliest branch of the Aetosauria lineage, being a sister group of the clade composed of Revueltosaurus plus Aetosauria; (5) earliest branch of the Paracrocodylomorpha lineage, being a sister group of the clade composed by Ticinosuchus ferox (Krebs, 1965) plus Paracrocodylomopha; and (6) earliest branch of Avemetatarsalia (Fig. 1C). Butler et al. (2014) considered Erpetosuchidae as a wild taxon, also revealing this unstable position in the evolution of Archosauria, with the consensus tree from this analysis being poorly resolved and displaying a major polytomy at the base of Archosauria. In the present analysis, the strict consensus (see Supporting Information, Appendix S1, S2) reveals a similar topology. However, there is a polytomy at the base of the pseudosuchian lineage, formed by Erpetosuchidae, Ornithosuchidae, the clade composed by Revueltosaurus plus Aetosauria, and the clade composed by Gracilisuchidae plus T. ferox and Paracrocodylomorpha. Accordingly, the alternative positions of Erpetosuchidae as a sister group of T. dabanensis or an early branch of Paracrocodylomorpha or an early branch of Avemetatarsalia were not supported with this analysis. Furthermore, the result of unstable taxa analysis (Pol & Escapa, 2009) excluded the alternative position of Erpetosuchidae as an early branch of Pseudosuchia or an early branch of the Aetosauria lineage (sister group of Revueltosaurus plus Aetosauria). The results of the analysis reveal, before one iteration, only two possible positions of Erpetosuchidae among the most parsimonious trees: as a sister group of Ornithosuchidae, composing an early branch lineage of Pseudosuchia, or a sister group of the clade composed of a polytomy among Gracilisuchidae, T. ferox plus Paracrocodylomorpha. A brief consideration of this latter clade is needed. Nesbitt (2011) considered Ticinosuchus to be a sister group of Pararocodylomorpha, a clade composed by Poposauroidea (including Qianosuchus mixtus, Poposaurus gracilis, Shuvosaurus inexpectus and their related taxa) plus Loricata (including P. chiniquensis, S. galilei, Rauisuchidae, Crocodylomorpha and related taxa). Paracrocodylomorpha is phylogenetically defined as a node-based clade composed of the least inclusive clade containing Poposaurus and Crocodylus niloticus Laurenti, 1768 (Nesbitt, 2011). In this sense, Paracrocodylomorpha is revealed in the present analysis, although it would not be accurate if Ticinosuchus belongs to this group or if it is the sister group. Likewise, it is important to consider that other phylogenetic analyses support Phytosauria as an early branch on Pseudosuchia (e.g. Brusatte et al. 2010; Ezcurra, 2016), contrasting with the analysis of Nesbitt (2011) and probably influencing the relative topology on Pseudosuchia with polarization/optimization of character states among transformational series. When constraint among Erpetosuchidae and Ornithosuchidae was forced, it resulted in 180 most parsimonious trees, with zero Bremer support. The only controversial synapomorphy for this clade is the presence of anteroposteriorly longer than wide dorsal presacral osteoderms, shared by P. candelariensis, E. granti (NHMUK R3139R) and O. woodwardia (HHMUK R2410), whereas the osteoderms of Parringtonia (NHMUK R8646) are squared, those in R. tenuisceps (PVL 3827) are wider than long, and none in V. rusconii (Bonaparte, 1972; von Baczko et al., 2014) is preserved (character 407). A previous preliminary analysis of P. candelariensis (Lacerda et al., 2016), proposed it as an early branch of Ornithosuchidae. However, this analysis did not incorporate E. granti and P. gracilis, and some character states were modified with a more accurate revision of the anatomy, as well as CT scan analysis (e.g. the relative inclination between premaxilla and maxilla is not sustainable; the number of premaxillary teeth and number and position of the maxillary ones was revealed only by means of X-ray images). The alternative position of Erpetosuchidae, as a sister group of a clade composed by Gracilisuchidae and Paracrocodylomorpha plus Ticinosuchus, also has zero Bremer support. However, the clade composed by Erpetosuchidae plus Paracrocodylomorpha is supported by two synapomophies: presence of ventromedial process on the articular (character 157), being reversed to absence on G. stipanicicorum (Romer, 1972; Butler et al., 2014) and some Poposauroidea (Nesbitt, 2011) (S. inexpectus, Effigia okeeffeae and Lotosaurus adentus); and the scapula bearing a teardrop-shaped tuber on the posterior edge for attachment of m. triceps (character 219), being reversed on P. kirkpatricki (Chatterjee, 1985; Weinbaum, 2013), Crocodylomorpha and Loricata (Nesbitt, 2011), whereas in P. candelariensis this character is placed as missing data because this bone was not preserved. The Erpetosuchidae clade displays a low support, with a Bremer value of one and Bootstrap at 64. Two synapomorphies support this clade and are found in all three members: maxillary teeth only present on the anterior region of bone (character 17), being present in only O. woodwardi (NHMUK R2409, R3143); and maxillary region ventral to the lacrimal has a mediolateral height greater than its dorsoventral length (character 21), converging with only L. adentus and E. okeeffeae. In addition, two synapomorphies support a closer relationship among E. granti and P. gracilis: absence of tooth serration (character 168); and a longitudinal bend on the dorsal presacral osteoderms (character 404), also converging with Euparkeria capensis (SAM PK5867, 6047, 6049), Gracilisuchidae (Butler et al., 2014), B. kupferzellensis (SMNS MHI 1895); Fasolasuchus tenax (PVL 3850); Rauisuchidae (BSPG AS XXV 92, 97; Chatterjee, 1985; Weinbaum, 2013) and several crocodylomorphs (Nesbitt, 2011). DISCUSSION Erpetosuchidae is formally represented by only two taxa: P. gracilis, from the Middle Triassic (Anisian) Lifua Member of the Manda Beds of Tanzania, and E. granti, from the Late Triassic (Carnian) Lossiemouth Sandstone Formation of Scotland (Fig. 9). An incomplete fragmentary skull is referred to Erpetosuchus sp. by Olsen, Sues & Norell (2000) from the Late Triassic (Norian), New Haven Formation of Connecticut, USA. The osteology of Erpetosuchidae is poorly understood, because to date there is no complete specimen described, with species based only on fragmentary materials of skull and postcranial elements, influencing the phylogenetic affinities hypothesis (Nesbitt & Butler, 2012). Although P. candelariensis is mostly represented by cranial material, it is sufficient to propose a new taxon for the Middle–Late Triassic (Late Ladinian–earliest Carnian) of southern Brazil, and the comparative osteological and phylogenetic analysis indicates a strong case for assigning it to this clade as the earlier branch taxon. Figure 9. View largeDownload slide Temporal distribution of the different geological units that bear Erpetosuchidae and Ornithosuchidae taxa and their paleogeographical location. Based on Olsen, Sues & Norell (2000), Benton & Walker (2002), Nesbitt & Butler (2012) and von Backzo & Ezcurra (2013). Temporal constraints are based on International Chronostratigraphic Chart (ICS) 2016 chart; global map modified from Nesbitt et al. (2013). Figure 9. View largeDownload slide Temporal distribution of the different geological units that bear Erpetosuchidae and Ornithosuchidae taxa and their paleogeographical location. Based on Olsen, Sues & Norell (2000), Benton & Walker (2002), Nesbitt & Butler (2012) and von Backzo & Ezcurra (2013). Temporal constraints are based on International Chronostratigraphic Chart (ICS) 2016 chart; global map modified from Nesbitt et al. (2013). In addition to this, P. candelariensis displays clear features that are characteristic of Ornithosuchidae, such as the Y-shaped ascending process of the jugal and the distinct articulation of the anterodorsal process of the maxilla with the nasals, but differs from this group by having only four premaxillary teeth, no downturned rostrum and no diastema at the premaxilla–maxilla contact. Compared with Erpetosuchidae, Ornithosuchidae is better known, being represented by three taxa: O. woodwardi (Newton, 1894; Walker, 1964; von Baczko & Ezcurra, 2013) from the Lossiemouth Sandstones Formation of Scotland (Late Carnian–earliest Norian), V. rusconii (Bonaparte, 1970; von Baczko et al., 2014) from the Ischigualasto Formation (Late Carnian–earliest Norian) and R. tenuisceps (Bonaparte, 1967; von Baczko & Desojo, 2016) from the Los Colorados Formation (Middle Norian), both from Argentina (Fig. 9). This clade has historically been considered an odd but important group in the early evolutionary history of pseudosuchians (Brinkman, 1981; Chatterjee, 1982; Cruickshank & Benton, 1985; Novas, 1989; Sereno, 1991; Parrish, 1993; von Baczko & Ezcurra, 2013), which diverges from the rest of Archosauria by the presence of an apomorphic ‘crocodile-reversed’ ankle joint (Chatterjee, 1982). Similarities between Erpetosuchidae and Ornithosuchidae were described by Huene (1939) and Nesbitt & Butler (2012), but these were mostly superficial owing to the incomplete or fragmentary preservation of the taxa and have not been explored further in the literature. Erpetosuchidae as sister taxon to Ornithosuchidae would indicate that the evolutionary history of this lineage is more complex than previously thought and considered. This mirrors what recent studies have proposed (e.g. Nesbitt et al., 2014, 2015; Ezcurra, 2016; Ezcurra & Butler, 2015; Pinheiro et al., 2016; Stocker et al., 2016), where Triassic archosauriforms display a richer evolutionary history than previously appreciated. Alternatively, the phylogenetic analysis reveals that Erpetosuchidade also has affinities with the clade Gracilisuchidae plus Paracrocodylomorpha. This closer relationship is based on the presence of a ventromedial process on the articular, and the scapula bearing a teardrop-shaped tuber on the posterior edge for the attachment of the m. triceps. However, among Erpetosuchidae taxa, both characteristics are only preserved and scored in E. granti. In this sense, these morphologies present in P. candelariensis cannot be representative of the Erpetosuchidae clade, indicating a case of morphological convergence with paracrocodylomorphs or an autapomorphic condition for this taxon. To clarify this, more information on E. granti and P. gracilis is needed, which will require new specimens. Additionally, P. candelariensis is the first member of the Erpetosuchidae described from southwestern Pangea. The chronologically older and more derived P. gracilis indicates a complex diversification history of these forms that presents many interesting questions for future work in Triassic archosauriform evolution. Furthermore, there are other factors that must be analysed, such as the role that the major biotas played in the evolution of these linages, given that P. candelariensis belonged to a highly competitive trophic web (the Dinodontosaurus Assemblage Zone) and co-habitated with some similar forms that probably shared similar habits, such as medium-sized carnivores like D. quartacolonia and the much larger P. chiniquensis. CONCLUSION The present work describes the new taxon P. candelariensis from the Middle–Late Triassic (Ladinian/Carnian) of Brazil, representing the earliest diverging branch of Erpetosuchidae. Our phylogenetic analysis reveals a modified interpretation of pseudosuchian evolution, with two possibilities for Erpetosuchidae relationships: an early branch of pseudosuchians, being a sister group of Ornithosuchidae; or a closer relationship with the clade composed by Gracilisuchidae and Paracrodylomorpha. Unfortunately, the specimen lacks most of its postcranial skeleton, preventing a more accurate comparison among pseudosuchians. On the time distribution, the new taxa from the Ladinian/Carnian age fills the temporal gap in the Erpetosuchidae clade, between P. gracilis from the Anisian and E. granti from the late Carnian–Norian. SUPPORTING INFORMATION Additional Supporting Information may be found in the online version of this article at the publisher’s website: Appendix S1. Rare earth element analysis. Appendix S2. Phylogenetic analysis. ACKNOWLEDGMENTS We would like to thank Agustin Martinelli, Bianca Mastrantonio, Bélen von Baczko, Julia Desojo, Max Langer, Martin Ezcurra and Voltaire Paes Neto for the useful discussions on Triassic archosaur evolution and diversity. We thank Felipe Pinheiro, Tomaz Melo and Marcos Sales for the discussions that helped in choosing the name of the taxon. The photographs were skillfully taken by Luiz Flávio Lopes (UFRGS). 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Oldenbourg, Munich, 900 pp. APPENDIX Measurements of the skull (left side) and postcranial elements in MMACR-PV-036-T (in centimetres) Skull length  34.2  Skull maximal height  11.5  Premaxilla body length  5.2  Premaxilla body height  3.5  Maxilla maximal length  13.6  Maxilla maximal height  5.3  Antorbital fenestra length  4.5  Antorbital fenestra height  1.3  Nasal length  14.3  Lacrimal length  6.4  Lacrimal height (exposed in lateral view)  4.2  Frontal width  5.7  Prefrontal length  6.7  Prefrontal width  3.3  Orbit length  4.4  Orbit height  4.8  Frontal length  7.8  Supratemporal fenestra length  4.7  Supratemporal fenestra width  4.9  Quadratojugal length  10.2  Parietal maximal width  12.6  Parietal minimal width  1.2  Supraoccipital height  4.2  Supraoccipital width  11.7  Left mandible length  38  Vertebral centrum length  4.7  Vertebral centrum width  3.8  Skull length  34.2  Skull maximal height  11.5  Premaxilla body length  5.2  Premaxilla body height  3.5  Maxilla maximal length  13.6  Maxilla maximal height  5.3  Antorbital fenestra length  4.5  Antorbital fenestra height  1.3  Nasal length  14.3  Lacrimal length  6.4  Lacrimal height (exposed in lateral view)  4.2  Frontal width  5.7  Prefrontal length  6.7  Prefrontal width  3.3  Orbit length  4.4  Orbit height  4.8  Frontal length  7.8  Supratemporal fenestra length  4.7  Supratemporal fenestra width  4.9  Quadratojugal length  10.2  Parietal maximal width  12.6  Parietal minimal width  1.2  Supraoccipital height  4.2  Supraoccipital width  11.7  Left mandible length  38  Vertebral centrum length  4.7  Vertebral centrum width  3.8  View Large Skull length  34.2  Skull maximal height  11.5  Premaxilla body length  5.2  Premaxilla body height  3.5  Maxilla maximal length  13.6  Maxilla maximal height  5.3  Antorbital fenestra length  4.5  Antorbital fenestra height  1.3  Nasal length  14.3  Lacrimal length  6.4  Lacrimal height (exposed in lateral view)  4.2  Frontal width  5.7  Prefrontal length  6.7  Prefrontal width  3.3  Orbit length  4.4  Orbit height  4.8  Frontal length  7.8  Supratemporal fenestra length  4.7  Supratemporal fenestra width  4.9  Quadratojugal length  10.2  Parietal maximal width  12.6  Parietal minimal width  1.2  Supraoccipital height  4.2  Supraoccipital width  11.7  Left mandible length  38  Vertebral centrum length  4.7  Vertebral centrum width  3.8  Skull length  34.2  Skull maximal height  11.5  Premaxilla body length  5.2  Premaxilla body height  3.5  Maxilla maximal length  13.6  Maxilla maximal height  5.3  Antorbital fenestra length  4.5  Antorbital fenestra height  1.3  Nasal length  14.3  Lacrimal length  6.4  Lacrimal height (exposed in lateral view)  4.2  Frontal width  5.7  Prefrontal length  6.7  Prefrontal width  3.3  Orbit length  4.4  Orbit height  4.8  Frontal length  7.8  Supratemporal fenestra length  4.7  Supratemporal fenestra width  4.9  Quadratojugal length  10.2  Parietal maximal width  12.6  Parietal minimal width  1.2  Supraoccipital height  4.2  Supraoccipital width  11.7  Left mandible length  38  Vertebral centrum length  4.7  Vertebral centrum width  3.8  View Large © 2018 The Linnean Society of London, Zoological Journal of the Linnean Society This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

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