Subject:
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Re: Evidence of Warm Blooded Dinosaurs
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Newsgroups:
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lugnet.off-topic.fun
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Date:
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Wed, 26 Apr 2000 00:26:25 GMT
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Viewed:
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387 times
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Jeff Stembel wrote:
> In lugnet.off-topic.fun, Lindsay Frederick Braun writes:
> > 1. Dromaeosaurs and Cretaceous coelurosaurs (an outdated term, as it
> > conflates several distinct lineages) in fact are *back-evolved* from the first
> > birds, based upon structural information, metabolic clues, and evidence of
> > later (post K-T) bird back-evolution into large ground predators; and
>
> I find this hard to swallow. What happened to their skulls and the wishbone?
> It is true that some birds later evolved into Dinosaur-like creatures(1), but I
> wouldn't use that to say some Dinosaurs evolved from birds.
That's just it--the distinction is unclear. The thought is that some late
dromaeosaurs have archaeoptergyian skeletal features that really shouldn't have
evolved independently unless the former were secondarily flightless. For example,
what use would developing hollow bones be to a dromaeosaur, unless it was
originally a flight adaptation? Why do the arms fold in that magnificently avian
way? It could be independent development, but mathematically it's unlikely.
Take a look at it--it's a good read even if you don't buy Paul's reconfiguration of
Cretaceous coelurosaurs. He has a lot of good encyclopaedic material, and a guide
to the "revised" phylogeny in the back replete with copious sketches of specimens
*and* lots of conjectural life-drawings.
> > 2. Amateur and professional fossil-hunters both are guilty of mucking up the
> > Archosaurian family tree by vainly trying to name "their own" dinosaur, and
> > thus giving specimens we can today quite readily tell are male, female, or
> > juvenile, three different genera names. Paul clears a lot of this up, and
> > apparently he made some people not-too-happy by suggesting that "their"
> > dinosaur be collapsed into another category.
>
> I'm not sure why this is so terrible, other than making it seem like there are
> more Dinosaurs than there actually are...
Well, it confuses phylogenies, and causes later speciments to be misinterpreted.
It doesn't change the number of dinosaurs, but it does change the number of
dinosaur types we think existed. Further, dividing out male/female/juvenile as
specific species, we gain no understanding of their likely behaviour. (Remember
the recent case when oviraptors were discovered among nests presumed to be those of
other dinosaurs, and it turned out that the nests were *Oviraptor* eggs? Rookery
behaviour! The embryos had hitherto been assigned to a different species, IIRC.)
> > There's a corollary to this, and that's that birds should not be in a separate
> > taxonomic class (Aves). Rather, they should be a subclass under Archosauria
> > (which should be a class, not a subclass of Reptilia as it's accepted
> > now--Archosauromorpha). To call birds non-archosaurs is like calling bats
> > non-mammals, just because they can fly.
>
> I don't think many people could stomach putting two such different creatures as
> Crocodiles and Hummingbirds in the same class. :) Also, there is more than
> just flight to differentiate Birds and reptiles. The Wishbone, for example.
> :) I'm sure I could come up with more if I knew more about birds. :)
I'm not sure a wishbone is even a defining feature. Don't some late stenonchysaurs
have rudimentary wishbones too? I'll have to check.
> > I'm in basic agreement--although the relation of dinosaurian groups is kind of
> > weird right now, because I've been seeing a lot of material lately that
> > suggests the "traditional view" separating dinosaurs by hip type is just plain
> > silly, and that separating them by size is also just plain silly.
>
> Can you present some of this material? I seem to've missed it. :) I do think
> the hip classification can be misleading, considering birds evolved from the
> "lizard hipped" Saurichians. ;)
Ack, I'll need to do the reference thing myself before I can start citing studies.
:) This may have to wait until after 10 May!
> 1 - Axebeak/Terror Bird being the prime example. Are these two the same, or
> separate species? What other examples are there?
Sort of--there were two main lineages in the Eocene, and more, newer lineages in
the Pliocene/Pleistocene South American fauna. Paul juxtaposes the two
evolutionary instances with the rise of the sickle-claws and their ilk, and it's
surprisingly similar (except that the later cases have more clearly avian
features).
best
LFB
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Message is in Reply To:
 | | Re: Evidence of Warm Blooded Dinosaurs
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| (...) I've never heard of it, so I'll have to check this book out. :) (...) I find this hard to swallow. What happened to their skulls and the wishbone? It is true that some birds later evolved into Dinosaur-like creatures(1), but I wouldn't use (...) (25 years ago, 25-Apr-00, to lugnet.off-topic.fun)
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