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

Re: Theropod "migrations"



I wrote:

<<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.>>

and Larry Febo wrote:
 
<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??>

  Hmm? No. Kimmeridgian and Tithonian are Late
Jurassic, and the Morrison is in the lastest late
Jurassic. At such an early, late J--early K period as
when *Iliosuchus* and *Stokesosaurus* stalked
Euamerica, there was an occasion (or occasions) of a
bridge between NAmerica and Europe, especially the
Britain--Spain--France complex, which would have
facilitated an interchange between the continents.
tyrannosaurs could have developed in Europe, migrated
into Asia via America, spawning *Siamotyrannus*, then
reentering America, along with, it may seem,
ornithomimosaurs (*Pelecanimimus* in Spain)
troodontids (possibly *Ornithodesmus,* the
little-butted one, in England) and *Iguanodon* and
*Camptosaurus*, not to mention *Pleurocoelous.*
Europoe may therefore be the breadbasket of all our
favorite dinos.

<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.>

  Asia and NAmerica have had a long, historic
association geologically, back all the way through the
Mesozoic, occasionally farther than not, occasionally
closer. Never a dull moment with these two. Bering
bridges were apparently quite common in the late K,
given the percieved faunal interchanges seen in
tyrannosaurs, oviraptorosaurs, ornithomimosaurs,
dromaeosaurs, "protoceratopians," and
pachycephalosaurs.

<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???>

  That's the monkey-wrench.

  The final contact Australia had with the rest of
Gondwana was about Turonian time, when the only oher
peice of land it was connected to was Antarctica, and
that was an isolated landmass since apparently the
Hauterivian (EK). So if there _were_ oviraptorosaurs
in Australia, they had to have gotten there (via
SAmerica was the only presently known way) by the
earliest EK (eEK!), or the LJ, even though those
fossils are [possibly] Albian in age. African dromies
and ovis are easier to deal with, if they were there,
since there were several clear bridges between the
north and south at that time. SAmerican ovis for the
same reason. They would have just emigrated from
America via Europe then Africa, and this fossil, also
[possibly] Albian in age, along with most of the
Santana fossils.

  The problem with the Aussie bones is that one (the
?surangular) may or may not be what it appears to be.
The other, a dorsal vertebra, has a single side
pleurocoel (forgive the redundancy), but so do several
other groups of theropods, including ornithomimosaurs.
And we all know about *Timimus*, right?

  Fare thee well,

===
- 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