Re: Tyrannosaurs with leathery skin, etc.

["Mickey Mortimer" <mickey_mortimer@email.msn.com>]

Nick Longrich wrote-

>With respect to Sinosauropteryx-
> The manus is tridactyl from everything I've heard/seen, but
>Sinraptor's fourth metacarpal wasn't associated with the manus.
> On the one hand, it seems strange an allosaur should have MC IV,
>on the other, I don't really know what else that bone would be. It could be
>that there is some homoplasy there- on yet the other hand, perhaps three
>digits is an Allosaurus-Sinosauropteryx synapomorphy.

Are you suggesting that Sinosauropteryx is an allosaurid, or that Allosaurus
is closer to coelurosaurs than Sinraptor?  Of course, what also messes the
"MC IV absent" synapomorphy up is it's presence in Coelurus, which is really
close to compsognathids in my analyses.

> Regarding tooth serrations, the new AMNH troodont has needlelike
>teeth completely devoid of serrations.

Can't blame me for not knowing unpublished data. ;)

>I really don't know that
>Sinosauropteryx' arms can be compared to Compsognathus. First of all, the
>radius in the type is missing and its imprint may not even give an accurate
>picture of its size; second the digits are long and slender, not at all
>like the stumpy and powerful thing you see on the thumb of Sinosauropteryx.

Strange, the photo I have of Compsognathus' type has the proximal portion of
the right radius preserved and most of the left (although it's overlapped by
the right ulna).  It seems to match the distal imprint fairly well.

>With respect to the tail, maybe I'm wrong on this one- it looks to me like
>there are ridgelike transverse processes out on the distal caudals;
>certainly there are still large neural spines and this isn't a point about
>it's affinity or lack thereof to Compsognathus, merely that I doubt it is
>particularly close to birds.

I guess the transverse processes could go out that far, I can't tell in the
photos I have.  Even so, I agree with you- I'm not advocating that the
reduced number of transverse processes in compsognathids (four+? in Sino and
0 in Compy) indicates a close relationship to birds.  Compsognathids have
less transverse processes than ornithomimids, Alxasaurus, most
oviraptorosaurs and velociraptorines (which are all higher up in my
phylogeny) , so even in my hypothesis developed this in parallel to
avialians.

> Also, if the comments on the ilium and ischium refer to GMV 2124,
>which is the larger of the two theropods on display in the National
>Geographic exhibit and splashed over two pages of their feathered dinosaur
>issue, there are questions about whether this is, in fact, a
>Sinosauropteryx, so it can't really be brought into the debate. The second
>animal published by Chen et al. in Nature does appear to be
>Sinosauropteryx, judging by its first digit.


D'oh!  My mistake.  I automatically assumed that the large Sino at the RTMP
was the large Sino in Chen et al.. Yes, the pelvic observations were
referring to GMV 2124.  It's a lot easier to interpret than the small
specimen.  Still, the ilium in NIGP 127586 also slopes caudoventrally in
Chen et al.'s figure.  I have the same question as Tim.  Why wouldn't this
be Sinosauropteryx?

Mickey Mortimer