RE: Sinosaurus (theropod from Early Jurassic of China) braincase anatomy (free pdf)

[Mickey Mortimer <mickey_mortimer111@msn.com>]

It's great to have more info about this theropod, but does anyone else find it 
backwards that we're getting this series of detailed papers on 'Sinosaurus 
triassicus' but based on Dilophosaurus sinensis specimens, before any evidence 
has even been presented that sinensis is a synonym?  Maybe Currie et al. have 
some amazing dental autapomorphies up their sleeves, in which case ignore the 
rest of what I write here.  But the holotype of Sinosaurus triassicus is REALLY 
fragmentary- a maxillary fragment four alveoli long, another three alveoli long 
that Young though probably belonged to the maxilla, a third jaw fragment with 
two alveoli that Young couldn't even identify to the element, and three teeth.  
These are the kinds of remains that are generally not considered diagnostic 
between pseudosuchians and basal theropods, let alone diagnostic for particular 
basal theropod species.  I fear the rationale will be along the lines of "the 
teeth are identical and they're from the same for
 mation", but we don't let this work for other taxa (Suchosaurus vs. Baryonyx, 
Antrodemus vs. Allosaurus, Manospondylus vs. Tyrannosaurus, etc.), and would be 
surprised if the Sinosaurus holotype could be distinguished from e.g. 
Cryolophosaurus or Dracovenator.  It's easy to then imagine someone twenty 
years down the line realizing this after Sinosaurus triassicus has been the 
established name for the Lufeng skeletons, then petitioning the ICZN to make a 
Dilophosaurus sinensis skeleton the neotype of Sinosaurus.  This would be 
deciding names by fiat (look at the Allosaurus, Stegosaurus and Plateosaurus 
examples today) instead of by which specimens are diagnostic, which is not how 
I think it should be done.

Mickey Mortimer

----------------------------------------
> Date: Tue, 16 Dec 2014 11:27:01 -0800
> From: bcreisler@gmail.com
> To: dinosaur@usc.edu
> Subject: Sinosaurus (theropod from Early Jurassic of China) braincase anatomy 
> (free pdf)
>
> Ben Creisler
> bcreisler@gmail.com
>
> A new paper (in open access at the link):
>
>
> Xing Lida, 

> Zhang Jianping, Wang Tao, Michael E. Burns & Dong Zhiming (2014)
> Braincase Anatomy of the Basal Theropod Sinosaurus from the Early
> Jurassic of China.
> Acta Geologica Sinica 88(6):1653-1664 (English Edition)
> http://www.geojournals.cn/dzxben/ch/reader/view_abstract.aspx?file_no=201406002&flag=1
>
>
>
> The neuroanatomy of the mid-sized theropod Sinosaurus triassicus from
> the Lower Jurassic Lufeng Formation, Lufeng Basin in Yunnan Province,
> China was studied using X-ray computed tomography. The braincase is
> characterized by a large supraoccipital knob that is capped by a
> posterior projection of the parietal and two external foramina for the
> caudal middle cerebral vein, which is completely enclosed by the
> supraoccipital. The basicranium has well defined, short basipterygoid
> processes that project ventral to the basal tubera. The basisphenoid
> is expanded, projects posteroventrally, and is pierced by four
> pneumatic recesses. The endocranial morphology resembles that observed
> in other basal theropods—in particular some allosauroids—and has a
> strongly marked pontine flexure and a large dorsal expansion. The
> inner ear morphology is also similar to that observed in other basal
> theropods, with slender semicircular canals. The anterior semicircular
> canal is 20% larger than the posterior semicircular canal, and the
> angle formed between them is less than 90° when seen in dorsal view.