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Re: AW: Tawa hallae: everything you know about basal saurischians is wrong...
Evelyn Sobielski <firstname.lastname@example.org> wrote:
> Is there any evidence for this claim?
I agree with Augusto on this one. The bipedality and high BMR inferred for
_Tawa_ and other early saurischians lends support to the presence an insulatory
body covering. Also, I know that the homology of these structures has been
questioned, but the presence of fuzz/down/hair-like integumentary structures in
representatives of Theropoda, Ornithischia and Pterosauria does at least make
you wonder how pervasive these structures were.
> (And has anybody ever checked GenBank whether the "feather"
> genes have some sort of viral signature? A "domesticated"
> papillomavirus or similar would explain the structurally
> different but physiologically somehow related - as
> integumental hyperplasies triggered by a fairly simple
> genetic mechanism, essentially - structures phylogenetically
> widespread among archosaurs. But its genetic "footprint"
> would be obvious, and thus this assumption could be
Sorry, I'm having a hard time interpreting what you mean here.
> Nonwithstanding, I find the notion of sticking feathers
> everywhere a bit dubious; eventually it's likely to result
> in major embarrassment and a lot of cheering from BANDits.
> Feathers/fuzz and large-bodied animals living in a tropical
> climate and well on their way to homothermy do not at all
> mix well. Phylogenetic bracketing is also unhelpful with
> such a limited sample of hard evidence; _Elephas_ and
> _Heterocephalus_ for example would provide a nice bracket
> that "proves" all mammals, big and small, are almost nude,
> if we did not know as many mammals as we do.
Doesn't this argue against your point? Big mammals have secondarily lost their
extensive hairy body covering. If the dino-fuzz in _Tianyulong_ is homologous
to the feathers (and proto-feathers) of theropods, then it is pretty much
guranteed that this kind of integument is primitive for dinosaurs.
> Absence of quill knobs (and possibly rectrical knobs, which
> are as of yet unknown but might conceivably have evolved as
> alternative to a pygostyle) in a large-bodied non-polar
> non-flying archosaur, I'd presume, is strongly indicative
> that the critter had no integumentary fuzz, feathers or
> bristles to significant extent.
Some modern flying birds lack quill knobs. _Velociraptor_ has quill knobs, and
it didn't fly. So again, sorry, your point escapes me.