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Re: When did the comsognathid lineage end? (fwd)



HP Nick Gardner wrote:

> As I understand it, the unnamed Santana form and Aristosuchus are also
> considered to be compsognathids.  I believe that the former was described
in
> the Canadian Journal of Earth Sciences but I do not know the citation.  O.
> Rauhut believed Koparion to also be a compsognathid but most other
> researchers recognize it as a very basal troodontid.
>
And I suspect that Nquebasaurus is also soms sort of compsognathid based on
the overall similarities between it and Sinosauropteryx + Compsognathus,
like a relatively short arm when compared to the hindlimb. Furthermore, the
pubis is very similair to that of Sinosauropteryx and it appears to have the
characteristic "fan-shaped" dorsal neural arches for this genus. Other
similarities include a well developed deltopectoral crest and a poorly
developed proximal tibial crest (sorry, I have forgotten the correct name).
And the unnamed Solnhofen genus, which, according to some sources, might be
a new species of Compsognathid. It only comprimises of a complete skull and
a few cervical vertebrae, more might be present though, given the excellent
preservation we have all come to love from this formation and all I had to
go on was a partial photograph. Scipionyx is another small theropod, and
based on the pubic similarities to Compsognathus, might also be a
compsognathid, but it is based on a juvenile specimen so many other
distinctive characters are not present to code for a detailed analysis.

So based on these genera, it appears that the compsognathid lineage extended
to the lower Creteceous and than they died out for some reason, perhaps it
was due to their relatively primitive morphology when compared to theropods
like Deinonychus or Sinovenator.