Re: [dinosaur] Pelecanimimus postcranial anatomy

[Tim Williams <tijawi@gmail.com>]

It's great to see a thorough description of the _Pelecanimimus_
postcranium.  A great deal of emphasis is placed on the long forelimbs
and long hands.  In general, the variation in the shapes and
proportions of the manual elements (metacarpals, phalanges, unguals)
among ornithomimosaurs has been linked to functional diversity (e.g.,
also in Chinzorig et al., 2017).  But I'm not convinced this is the
case.  Beyond a function in hooking and clamping, I don't think
ornithomimosaur hands had any specialized function(s).  So I'm
skeptical that the disparity in manual morphologies among
ornithomimosaur taxa reflects adaptations to different ecological
niches.  Instead, it might be the result of drift.

In other words... ornithomimosaur hands didn't do very much. So,
functionally speaking, all the changes in individual bones probably
weren't very important.

Also, I'm not sure the new definition of Ornithomimosauria proposed by
Cuesta et al. is a good idea.  They suggest a node-based definition
for Ornithomimosauria: _Nqwebasaurus_ and _Ornithomimus_ and all the
descendants of their most recent common ancestor.  However, this
definition assumes that the current phylogenetic position of
_Nqwebasaurus_ is set in stone.  I thought the previous (stem-based)
definition of Ornithomimosauria by Lee et al. (2014) is far more
sensible:  _Ornithomimus_  and all taxa sharing a more recent common
ancestor with it than with _Allosaurus_ , _Tyrannosaurus_,
_Compsognathus_, _Alvarezsaurus_, _Therizinosaurus_,  _Deinonychus_,
_Troodon_, and _Passer_. Yes, the stem-based definition is quite a
mouthful - but all those external specifiers cater to many possible
topologies, making the content of clade Ornithomimosauria potentially
more stable and 'future-proof' (especially if _Nqwebasaurus_ shifts
position in theropod phylogeny, which is a non-zero possibility).


On Sat, May 8, 2021 at 12:48 AM Ben Creisler <bcreisler@gmail.com> wrote:
>
>
> Ben Creisler
> bcreisler@gmail.com
>
> A new paper:
>
> Elena Cuesta, Daniel Vidal, Francisco Ortega, Masateru Shibata & Josà L Sanz 
> (2021)
> Pelecanimimus (Theropoda: Ornithomimosauria) postcranial anatomy and the 
> evolution of the specialized manus in Ornithomimosaurs and sternum in 
> maniraptoriforms.
> Zoological Journal of the Linnean Society, zlab013
> doi: 
> https://urldefense.com/v3/__https://doi.org/10.1093/zoolinnean/zlab013__;!!LIr3w8kk_Xxm!6IofHGpw7xQx_-ypNPWRAPqTqElCD9mL85aSt0TmDu0WY1YG20QDfcdHM6OF2gxe$
>  
> https://urldefense.com/v3/__https://academic.oup.com/zoolinnean/advance-article-abstract/doi/10.1093/zoolinnean/zlab013/6271061__;!!LIr3w8kk_Xxm!6IofHGpw7xQx_-ypNPWRAPqTqElCD9mL85aSt0TmDu0WY1YG20QDfcdHM8MxqVEQ$
>  
>
>
> Pelecanimimus polyodon was discovered in 1993 in the Spanish Barremian fossil 
> site of Las Hoyas, being the first ornithomimosaur described from Europe. So 
> far, there has been no detailed description of the holotype of Pelecanimimus, 
> which is composed of the anterior-half of an articulated skeleton. Here we 
> report a new, detailed, revised and more accurate osteological description of 
> its postcranial skeleton, comparing this new data to information about 
> Ornithomimosauria from the last three decades. This osteological and 
> phylogenetic analysis of Pelecanimimus shows several ornithomimosaur 
> synapomorphies and a unique combination of characters that emend its original 
> diagnosis. Pelecanimimus diverged early in Ornithomimosauria and reveals an 
> enlargement trend of the manus, shared with derived ornithomimosaurians, due 
> to a long metacarpal I and elongated distal phalanges. This evolutionary 
> novelty, and other synapomorphies, has led to the definition of a new clade, 
> Macrocheiriformes, including Pelecanimimus and more derived ornithomimosaurs. 
> Pelecanimimus has the only ossified sternal plates among ornithomimosaurs and 
> the first evidence of uncinate processes in a non-maniraptoran theropod, 
> indicating a convergent appearance of these structures in Coelurosauria. The 
> character combination in an early-diverging ornithomimosaur like 
> Pelecanimimus found in this analysis provides a key step in the evolution of 
> the manus and pectoral girdle in Ornithomimosauria.
>
> ===
>
> Virus-free. 
> https://urldefense.com/v3/__http://www.avg.com__;!!LIr3w8kk_Xxm!6IofHGpw7xQx_-ypNPWRAPqTqElCD9mL85aSt0TmDu0WY1YG20QDfcdHM4XTabjg$
>