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Re: Bird reduce their "heating bills" in cold climates
--- On Mon, 7/5/10, David Marjanovic <email@example.com> wrote:
> From: David Marjanovic <firstname.lastname@example.org>
> Subject: Re: Bird reduce their "heating bills" in cold climates
> To: "DML" <email@example.com>
> 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
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
> > 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.
Assuming that it wasn't a preservational artifact, then that is already about
the same degree of flexibility seen in green iguana tails.