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Re: Theropod "migrations"
----- Original Message -----
From: Jaime A. Headden <firstname.lastname@example.org>
Sent: Saturday, April 24, 1999 3:01 AM
Subject: Re: Theropod "migrations"
> >OK, but what about T_Rex and its Asian counterpart
> >Tarbosaurus Baatar? Does the Tyrannosaurid line extend
>> back far enough to have been present when Gondwana was
> >whole? What about oviraptor?? What about
> Tarbosaurus Schmarbotaurus.
Schmarbotaurus??? (Dosen`t sound Asian....more Middle East? 8^)
>The tyrannosaurs as
> known never set foot on Gondwana; they're exclusively
> Laurasian, with one possible member in Thailand
> (*Siamotyrannus*) and another in England
> (*Iliosuchus*). Earliest *possible* tyrannosaur,
> *Stokesaurus*, was from the Kimmeridgian?--Tithotian
> of the Morrison, _after_ the north and south split.
OK, I already admitted my error substituting Gondwana for Laurasia. But ,
you say then that tyrannosaurs were Laurasian,meaning .....what? That their
line extends back to the Early Jurassic??
> Oviraptors? Apparently, this one's a mess _only_ if
> the Australian specimens (a "surangular" and a caudal
> vertebrae) are from oviraptorosaurs, which the
> describers do voice their doubts of; and the sacrum
> from Brazil, which frankly does not compare well with
> oviraptors in that there aren't pleurocoels on all
> sacrals, and _mostly_ pleurocoelous sacrals are known
> in most maniraptoriform theropods, like
> ornithomimosaurs and dromaeosaurs. Oviraptors just
> upped the ante. Oldest _secure_ oviraptorosaur,
> *Caenagnathasia* was possibly Turonian in age, and was
> quite Asian (Uzbek). *Microvenator* was Aptian--Albian
> from the Clovery, still Asiamerican. Cross--Berring
> distribution can be explained as all other forms
> crossing the bridge, as one major event. Hence
> *Elmisaurus* on both sides, *Chirostenotes* on one,
> and quite easily explained as one having given rise to
> the other (former to the latter; in cladistic terms
> that is, not _sensu_ ansector-descendant).
> Dromaeosaurs are even more simple. Dromaeosaurines
> stayed in America, begat the velociraptorines, and
> went to Asia in the Campanian (Judithian--Nemegtian),
> *Velociraptor* possibly being one of the
> bridge-crossers if GSP is right in finding
> *Deinonychus* the same genus as Vel, but that hardly
> matters, really.
> And *Saurolophus* is the only real single genus of
> herbivore that crossed the Berring bridge.
> *Brachiosaurus,* *Barosaurus,* and possibly
> *Pleurocoelus* may have gone the Eurasian way, popped
> into Africa before that bridge broke off.
So the here you are saying there was a "Bering Land Bridge" in the late
Cretaceous. Admittedly, my knowledge of ancient geology and continental
positions are not up to par, but, that`s why I consulted the web site
located at: http://vishnu.glg.nau.edu/rcb/Late_Cret.jpg
which , admittedly, dosen`t show the portion of the globe we are interested
in, but I can`t see how the Bering land bridge could exist that early. I
mean, the N American continent had a lot of westward travelling to do
(relatively speaking) to close that gap no? I (of course) may be wrong here.
I`ll have to look into it further. But what about all the other areas that
Oviraptors and Velociraptors have gotten into? Could land bridges have
developed there as well?? How?....I can see possibly between North and South
America, due to the subducting plate causing a string of Andean volcanoes
but what about Africa at that time, ...What about Australia???