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Figure 2 | Re-evaluating the evolution and biogeography of haramiyidans.
a, Huttenlocker et al.
analysed relationships between the early branches of
the family tree for mammals and their more primitive relatives. The resulting
evolutionary tree indicates that haramiyidans are not mammals, contrary to
some previous evidence
. The analysis also places the Cretaceous genus
Vintana in Haramiyida for the first time. b, Cretaceous haramiyidans (indicated
by green circles) have previously been found in northern Africa and possibly
India. The authors’ analysis expands the Cretaceous range of haramiyidans to
Madagascar (Vintana) and North America (Cifelliodon). Combined with the
fact that other fossils of haramiyidans from the Triassic (purple) have been
found in Europe and Greenland, and that haramiyidans from the Jurassic (blue)
have been found in Europe, China and Tanzania, this work implies a much
broader temporal and geographical distribution of haramiyidans than had
previously been hypothesized.
Triassic Jurassic Cretaceous
200250 100 50
Million years ago
that, although the Chinese haramiyidans are
represented by complete skeletons, the speci-
mens are essentially 2D. Most of the skulls are
little more than flattened outlines, which lim-
its their usefulness for informing mammalian
Cifelliodon is one of the first skulls
preserved in three dimensions from the hara-
miyidan lineage. As such, it is a crucial piece
of the evolutionary puzzle. Huttenlocker and
colleagues’ phylogeny puts Haramiyida (and
so Cifelliodon) outside Mammalia (Fig. 2a).
Thus, their work favours a model in which
early mammals diversified rapidly during the
Finally, Huttenlocker et al. provide evidence
that Cifelliodon is closely related to Cretaceous
species from northern Africa (Hahnodon
taqueti) and Madagascar (Vintana sertichi),
the latter of which had not previously been
assigned to Haramiyida. This implies a much
broader temporal and geographical distribu-
tion for Haramiyida than has been assumed
(Fig. 2b), indicating the need to reassess the
biogeographical history of the group. The
authors conclude that haramiyidans had
a global distribution during the Jurassic–
Cretaceous transition, and that land bridges
aiding vertebrate dispersal existed long after
the fragmentation of the super continent
Pangaea — much later than previously rec-
ognized. An alternative hypothesis that is
perhaps more consistent with current palaeo-
is that haramiyidans,
like many vertebrate groups, had a Pangaean
distribution in the Jurassic period and evolved
in isolation thereafter, as landmasses sepa-
rated during the Cretaceous period. The best
way to test these competing hypotheses is with
the discovery of more well-preserved fossils,
like this exquisite skull of Cifelliodon.
Simone Hoffmann is in the Department of
Anatomy, New York Institute of Technology,
College of Osteopathic Medicine, Old
Westbury, New York 11568, USA. David
W. K r a u s e is in the Department of Earth
Sciences, Denver Museum of Nature &
Science, Denver, Colorado 80205, USA.
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Schultz, J. A. & Luo, Z.-X. Nature 558, 108–112
2. Kielan-Jaworowska, Z., Cifelli, R. L. & Luo, Z.-X.
Mammals from the Age of Dinosaurs: Origins, Evolution,
and Structure (Columbia Univ. Press, 2004).
A fresh approach to
An avalanche of data is about to revolutionize astronomy, but the options for
validating those data have been limited. High-precision measurements from the
Hubble Space Telescope enable a much-needed alternative option.
ry this experiment: extend your thumb
at arm’s length and close one eye at a
time. Your thumb will seem to ‘jump’
between two positions as you switch the eye
that is closed. That jump is known as parallax.
If you measure the jump as well as the distance
between your eyes, you can use trigonom-
etry to calculate the distance to your thumb.
Astronomers use parallax, on a much greater
scale, to measure distances to astronomical
objects. Writing in The Astrophysical Journal
Letters, Brown et al.
report that they have
achieved this for the nearby star cluster
NGC 6397, using the Hubble Space Telescope.
Their method will provide a crucial means of
validating the wealth of parallax data released
this year from the European Space Agency’s
It is a challenge to find a topic in astronomy
that does not rely on the astronomical distance
7 JUNE 2018 | VOL 558 | NATURE | 33
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