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Re: [dinosaur] New Anchiornis specimens from Late Jurassic of China (free pdf)
Another genus bites the dust. April has been a bad month
(_Ugrunaaluk_ sunk into _Edmontosaurus_, and _Dawndraco_ sunk into
_Pteranodon_ - neither a huge surprise). Now _Aurornis_ is formally
regarded as a "likely" junior synonym of _Anchiornis_. The other
Jianchang County paravians, _Xiaotingia_ and _Eosinopteryx_, get a
stay of execution; both are provisionally maintained as valid taxa...
for the time being.
Pei et al. regard the differences between _Aurornis_ and _Anchiornis_
as being subsumed by intraspecific variation. For example,
_Anchiornis_ specimens show variation in the proportions of their
pedal phalanges - even within the same specimen! As a consequence,
I'd suggest that caution should be exercised when drawing ecological
inferences from the proportions of the pedal phalanges (including the
relative length of the penultimate phalanges) in basal paravians.
Although this can be useful for pedal proportions at the extreme ends
of the spectrum, especially in extant birds (ostriches have very
different pedal proportions to ospreys, for example), the feet of
basal paravians tend not to be highly specialized for grasping. This
applies to microraptorines and basal birds. (To belabor a point, I
think it's inadvisable to regard _Zhongjianosaurus_ as "arboreal"
simply because the penultimate phalanx of the third toe is slightly
longer than the phalanx before it.)
Similarly, Pei et al. also dispute the "elongated" metatarsal I
originally described for _Aurornis_, attributing this to
preservational artifact. Thus, metatarsal I of
_Anchiornis_/_Aurornis_ is not as distally located as it is in
_Epidendrosaurus_, _Archaeopteryx_, and _Jeholornis_, but is similar
to the condition in deinonychosaurs (including _Microraptor_).
Although some incipient perching ability is possible (if the paravian
was 'perched' on a very thick branch), this severely undermines the
hypothesis that basal paravians had arboreal habits (contra Falk et
al., 2016 doi:10.1371/journal.pone.0167284; Hattori et al. 2016 DOI:
10.1080/02724634.2016.1116995 - I don't mean to pick on these two
studies, they're just recent ones that come to mind).
On Sat, Apr 15, 2017 at 2:31 AM, Ben Creisler <firstname.lastname@example.org> wrote:
> Ben Creisler
> A new monograph in open access:
> Rui Pei, Quanguo Li, Qingjin Meng, Mark A. Norell, and Ke-Qin Gao (2017)
> New specimens of Anchiornis huxleyi (Theropoda, Paraves) from the late
> Jurassic of northeastern China.
> Bulletin of the American Museum of Natural History 411: 66 pp.
> ISSN 0003-0090
> Four new specimens of Anchiornis huxleyi (PKUP V1068, BMNHC PH804, BMNHC
> PH822, and BMNHC PH823) were recently recovered from the late Jurassic
> fossil beds of the Tiaojishan Formation in northeastern China. These new
> specimens are almost completely preserved with cranial and postcranial
> skeletons. Morphological features of Anchiornis huxleyi have implications
> for paravian character evolution and provide insights into the relationships
> of major paravian lineages. Anchiornis huxleyi shares derived features with
> avialans, such as a straight nasal process of the premaxilla and the absence
> of an external mandibular fenestra in lateral view. However, Anchiornis
> huxleyi lacks several derived deinonychosaurian features, including a
> laterally exposed splenial and a specialized raptorial pedal digit II.
> Morphological comparisons strongly suggest Anchiornis is more closely
> related to avialans than to deinonychosaurians or troodontids. Anchiornis
> huxleyi exhibits many conservative paravian features, and closely resembles
> Archaeopteryx and other Jurassic paravians from Jianchang County, such as
> Xiaotingia and Eosinopteryx. The other Jianchang paravian, Aurornis xui, is
> likely a junior synonym of Anchiornis huxleyi.