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

I'm fine with deciding names by fiat, when it's workers in the field
(paleontologists) who decide which specimens should carry the name,
albeit on a case-by-case basis.  Establishing a neotype is important
for entrenched genera such as _Iguanodon_, _Allosaurus_,
_Plateosaurus_, and _Stegosaurus_.  It may yet be necessary for
_Diplodocus_, another well-known genus.  In these cases, a neotype
helps ensure the continuity of a well-known genus, when the type
specimen is deemed to be indeterminate or of dubious diagnostic value.
I think this approach is good for the long-term stability of a name -
including in cases where the original type specimen is possibly
diagnostic, but of exceedingly poor quality.

But I don't always think this process is necessary - as in the cases
of _Coelophysis_ and _Cetiosauriscus_, which also came before the
ICZN.  For _Coelophysis_, I agree that a neotype might have been
necessary; but one could argue that the specimen chosen as neotype
(the holotype of _Rioarribasaurus_) was inapt.  For _Cetiosauriscus_,
I don't think this genus had accrued enough cachet to deserve being
salvaged as a valid genus via the designation of a neotype; the ICZN
disagreed.  But again, it was workers in the field who petitioned the

For _Sinosaurus_,  I agree that the type specimen looks very iffy -
but I'll trust to Currie &c to explain why they chose to refer
_Dilophosaurus sinensis_ to _Sinosaurus triassicus_, rather than make
the former the holotype of a new genus (which has the benefit of an
excellent type specimen).  I do agree it will take some "some amazing
dental autapomorphies " to justify the referral of _D. sinensis_ to
_Sinosaurus_.  If these shared characters are anything less than
amazing, I doubt _Sinosaurus_ will last the distance as a valid genus.
Let's check in at the end of 2034, and see how _Sinosaurus_ is faring!

Time-honored and fairly well-known genera that are based on dubiously
diagnostic material have often been discarded as nomina dubia - such
as _Titanosaurus indicus_.  Here, a case could have been made to refer
_Jainosaurus septentrionalis_ to _T. indicus_, and retain the latter
as a valid taxon.  Instead _Titanosaurus_ has been junked in favor of
_Jainosaurus_.  So there are parallels to the _Sinosaurus_/_D.
sinensis_ situation.  In general, because this approach is based on
the discretion of individual workers, there is a great deal of
inconsistency in the literature.  But I still think the decision
should be left to individual workers, and nomenclatural stability be
the major determinant.  For example, I'd hate to see _Tyrannosaurus_
sunk into _Manospondylus_, simply because the crappy type specimen of
_Manospondylus_ was deemed by someone to be diagnostic at the genus



On Wed, Dec 17, 2014 at 7:18 PM, Mickey Mortimer
<mickey_mortimer111@msn.com> wrote:
> 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 f
>  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.