COMPSOGNATHIDS or "COMPSOGNATHIDS"

[darren.naish@port.ac.uk]

Thanks indeed to Nick L for his thoughtful comments on some of the 
goings on at SVP. I'd like to briefly respond to some of his comments 
on the hypothesis of a monophyletic Compsognathidae, partly because 
I agree with him but also because I think there probably _is_ a 
coelurosaur clade that should be called Compsognathidae. 

A major part of my thesis was on _Aristosuchus_, a small coelurosaur 
from the Wessex Formation that's been much confused in the literature 
with _Calamospondylus oweni_, a name based on a different 
specimen. Interestingly, _Aristosuchus_ is just about identical to the 
Nice _Compsognathus_ specimen and lacks autapomorphies - in fact 
one could make a case for referring it to _Compsognathus_.  It can be 
regarded as a metataxon that might prove distinct - this is suggested by 
stratigraphy (I said suggested) and the size disparity between the 
specimens. Obviously it would be nice to test these ideas with better 
material and I can't ignore the possibility that the similarities represent, 
say, plesiomorphies among basal coelurosaurs. I'm writing up my work 
on this taxon (thus far it's only been presented as abstracts) and hope to 
see it published within the new two years. Another specimen, the 
recently described Brazilian coelurosaur SMNK 2349 PAL, is also 
identical (so far as we can tell) with _Compsognathus_, differing from 
it only in the asymmetrical features of the pelvis. This specimen was 
deemed unworthy of designation as a holotype as it also exhibits no 
autapomorphies (believe me, we've tried to find them...) and can be 
regarded as a metataxon. It certainly has the same fan-shaped neural 
spines and _Compsognathus_-like pubis as does _Compsognathus_. 
There are a lot of ifs here, but the implication  is that there is a 
coelurosaur clade that includes _Compsognathus_, _Aristosuchus_ 
and SMNK 2349 PAL.

Whether Compsognathidae includes _Sinosauropteryx_ is a different 
problem and, as Nick has discussed several times, in parsimony 
analysis this genus does not necessarily form a clade with 
_Compsognathus_. Phil Currie is supposed to be doing a big 
monograph on _Sinosauropteryx_ isn't he? More work and more 
coding of specimens is needed: in my analysis (I am probably sticking 
with NONA) there is no assumed monophyly of Compsognathidae and 
the separate specimens are being coded as OTUs. It is not my intention 
here to attempt to produce a definitive viewpoint, just to provide 
another perspective on the debate. If only all skeletons were preserved 
with all of their respective elements, and if all were accurately 
illustrated when published....

"There are three kinds of people: those that can count and those that 
can't"

DARREN NAISH 
PALAEOBIOLOGY RESEARCH GROUP
School of Earth, Environmental & Physical Sciences
UNIVERSITY OF PORTSMOUTH
Burnaby Building
Burnaby Road                           email: darren.naish@port.ac.uk
Portsmouth UK                          tel: 01703 446718
P01 3QL