--- On Mon, 7/5/10, David Marjanovic <david.marjanovic@gmx.at> wrote:
From: David Marjanovic <david.marjanovic@gmx.at>
Subject: Re: Bird reduce their "heating bills" in cold climates
To: "DML" <dinosaur@usc.edu>
Date: Monday, July 5, 2010, 2:07 PM
> Fuzzy integument is still
contentious for ornithischians (and
> unlikely IMO).
Doesn't *Tianyulong* show that it can happen?
++++++++++++++++++++++++++++++++++++++++++++
IF, what is preserved with _Tianyulong_ is actually related to the
specimen at all, and not some unrelated object (e.g. plant material,
bacterial film, parasite). That is something only further testing of the
fossil will show.
______________________________________
> Even if it turns out to be true for a few
species, it seems more
> likely that it was an independent development
rather than an inherent
> character (i.e. not feathers).
Given pterosaurs, saurischians, and *Psittacosaurus*, it
might well be a symplesiomorphy. (*Psittacosaurus* shows
that "quills" don't need to cover the entire body, so I'm
not saying the first ornithodiran was fuzzy all over!)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
You are oversimplifying here. "Saurischians" is really "maniraptors and a
couple of non-maniraptoran coelurosaurs. The majority of known saurischian
integument is scaly.
The "quills" in _Psittacosaurus_ may just be modified scales (their
presence adjacent to real scales would favour this position), or they
might be unrelated to fossil as well (they, too, have been questioned as
being possible plant material).
Assuming that all these fossils are preserving real integument, it is
still more parsimonious to assume that filamentous integument evolved on
four separate occasions (coelurosaurs close to Maniraptora,
Hypsilophodontids, _Psittacosaurus_, Pterosaurs), rather than the 7+
re-evolutions of a scaly covering that would be required if it was a
symplesiomorphy.
_____________________________________________________
> As for
sue.
[...]
OK.
> Another possibility is that Leaellynasaura might
have been arboreal,
> and the tail may have been used in a
semi-prehensile fashion as seen
> in modern day green iguanas.
The anatomy of the tail and the rest of the body make that
very unlikely, AFAIK.
++++++++++++++++++++++++++++++++++++++++++++++++++
Hardly anything about the skeleton of green iguanas, screams arboreal
either.
As for the tail, it seems to lack the ossified tendons of other
iguanodontians, though even if it did, the degree of "stiffness" conferred
by the ossified tendons, is not as much as was once thought (see Organ
2006).
Then there is the apparently flexed tail of a dromaeosaur that was on Tet
Zoo.
http://scienceblogs.com/tetrapodzoology/2008/08/dromaeosaur_tails.php
Assuming that it wasn't a preservational artifact, then that is already
about the same degree of flexibility seen in green iguana tails.
Jason