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Re: pneumatic bones
> > I've never heard of pneumatic caudal vertebrae in tyrannosaurids. What
> > is the reference?
> Have yet to find it (suffering from selective memory); it must be an SVP
> meeting abstract from 1998, 1999 or (improbably) 2000.
It is not in an abstract from 1998, and the paper on the pneumaticity of
*Archaeopteryx* states that in tyrannosaurs all presacral vertebrae are
pneumatic, it does not mention caudals. So I may suffer from wrong memory,
There are, however, lots of other interesting things in these sources.
Supplement 1 has a large introduction which reviews just about everything
that has been published between 1996 and 1998 on dinosaurs. Donald F. Glut
has visited Dinofest 1998; lots of photos of mounted skeletons come from
there, as does a summary of the wings-for-brooding hypothesis:
"A fresh and original (also rather provocative) hypothesis
regarding the possible evolution of flight feathers [...] was offered in a
brief report by Hopp and Orsen (1998) (also in a "poster" by Orsen and Hopp
1998), [...]. As acknowledged by these authors, it is difficut to comprehend
how wing feathers developed through short intermediate evolutionary stages
before becoming long enough to generate the adequate lift required for
flight. Rather than pursuing (as had earlier studies) lines of research
based upon the possible uses of feathers in primitive birds like
*Archaeopteryx*, Hopp and Orsen (also Orsen and Hopp) proposed a different
mechanism -- _i. e._, brooding, or the use of wing feathers to cover
protectively eggs or hatchlings -- as a selective pressure that possibly
originated the process of lengthening the arm and tail feathers."
As HP Thomas Hopp is onlist, I have a question -- why the tail
feathers, too? (Or has Glut misunderstood something?)
"[...] the authors noted two postural traits that are common among
modern brooding birds -- squatting with medial placement of the feet, and
extension of the forelimbs -- which ancient birds and even some of the
earliest theropods were capable of assuming. [...] This capability of
adopting the brooding postures observed in *Oviraptor*, the authors added,
also existed even in the most ancient of theropods. [...] The authors
further speculated that wing feathers may have been an early development in
theropod evolution existing in nonavian forms as far back as the Late
Triassic, more than 150 million years before *Oviraptor* and 80 million
years before *Archaeopteryx*."
Were all theropods capable of sprawling their arms like
deinonychosaurs, oviraptorosaurs and birds?
There is a nice entry for *Bagaraatan*. HP Mickey Mortimer wrote some months
ago "told you it's interesting!"; indeed it is. Are there any other animals
with that extra bone, the antarticular? Any with caudal centra that are
hollow and thin-walled, but not pneumatic? Any with such a small angular and
big surangular? The unusual proximal rigidity of the tail is considered an
adaptation for speed, but do ornithomimosaurs have something comparable?
Glut puts it into "?Avetheropoda _incertae sedis_", I don't have any
better idea. Mantra time -- give me more fossils!!!