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RE: Bird reduce their "heating bills" in cold climates
It should be noted that *Tianyulong confuciusi* is positioned as a
heterodontosaurid in Zheng et al., rather than in a hypothetical
"Hypsilophodontidae." Heterodontosauridae has an uncertain position in regards
to Ornithischia at large, being anywhere from at the base of Ornithischian
(non-genasaurian), outside Cerapoda (Marginocephalia + Ornithopoda), or even as
the sister-taxon to Marginocephalia. In at least two of these, the distance
between Heterodontosauridae and psittacosaurs is fairly close, making the
possibility of the integument being cerapodan or marginocephalian in origin.
Finding more basal squamation/extra-integumentation of this form in other, more
secure taxa would assist in determining the origin.
I should note, however, that the technical publications do not favor even a
plant-matter origin for the caudal structures in *Psittacosaurus* sp, and the
morphology in *Tianyulong confuciusi* for these has NOT been performed or at
least published upon in order to compare it. *Psittacosaurus* sp. (according to
either Mayr et al. or Lingham-Soliar) has both squamation and long caudal
"quills," and despite this, *Tianyulong confuciusi* appears to have integument
identical in preservation to various coleurosaurians (as a note: "maniraptora
and a few others" chould be "Coelurosauria," as *Sinosauropteryx* is positioned
at or near the base in some analyses, although it has been a while since it has
been recovered in such a spot).
One final note: There are more than two ways to stiffen a tail [that's what
she said]. *Tianyulong confuciusi,* however, does bear elongated, stiffening
rods bundled dorsally and ventrally to the vertebral column for most of its
tail, unlike *Psittacosaurus* sp. Yet despite this, the caudal flexure of tails
with stiffening rods has been generally considered a preservational artefact,
rather than a natural motility indicator.
Jaime A. Headden
The Bite Stuff (site v2)
"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion
> Date: Mon, 5 Jul 2010 12:11:50 -0700
> From: email@example.com
> To: firstname.lastname@example.org
> Subject: Re: Bird reduce their "heating bills" in cold climates
> --- On Mon, 7/5/10, David Marjanovic wrote:
>> From: David Marjanovic
>> Subject: Re: Bird reduce their "heating bills" in cold climates
>> To: "DML"
>> 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
>>> 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.
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