[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Theropod "migrations"



Tom the Holtz wrote:

<<And, again, I agree with Sereno on this: many of the
similarities among mid-Cretaceous faunas worldwide are
more likely due to mutual survival of populations
whose ancestral range included all these continents.
(In fact, if Rauhut is correct in allying some of the
Tendaguru teeth to the carcharodontosaurs, then this
group was present back at a time of much faunal
cosmopolitanism).>>

Larry febo wrote:

<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
Velociraptor???>

  Tarbosaurus Schmarbotaurus. 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.

  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.

===
- Greek proverb: "Knowledge is Inherent;
  Stupidity is Learned." -

Jaime A. Headden

Qilong, the we---is temporarily out of service.
Please check back when the phone lines are not busy.
_________________________________________________________
Do You Yahoo!?
Get your free @yahoo.com address at http://mail.yahoo.com