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Re: Aussie dinosaurs, and my questions.



>And now;
>
>In reply to me, Tom Holtz <tholtz@geochange.er.usgs.gov> said:
>
>> First off, I would suspect a route down SE Asia is more likely (appealing
>> to the facts that a) paleogeography of southeast Asia is currently
>> problematic,
>
>How problematic? I would have thought that 100 mya northern Australia
>was still a long way away from SE Asia, and all the islands (eg Bali, New
>Guinea) and island chains between SE Asia and N Aust hadn't been thrown
>up by Aust's collision with SE Asia...We can't be that uncertain about
>paleogeography can we?

Oh, my, yes we can!  There is no certainty even to the number of major
tectonic units that form SE Asia.  The whole Indian Ocean region is still
problematic with regards to paleolongitude - gives the plate jockies
something to work on.

>> b) the Thailand species of Psittacosaurus is the closest
>> ceratopsian to Australia and
>
>Hey, that's interesting, I wasn't aware that there was a Thailand species
>of Psittacosaurus..

There is also Siamosaurus (a possible spinosaurid), an iguanodontian, and a
couple of species of (non-titanosaurid) sauropods.

>> c) with the very questionable exception of
>> Notoceratops, no ceratopsian has been found in South America, Africa,
>> Antarctica, or India.
>
>Yeah, freaky isn't it? That's why I thought the whole idea of an Aussie
>ceratopsian might be a media beat-up.
>
>Where does Notoceratops come from? Sorry, I used to be able to rattle
>this stuff off the top of my head for hours when I was a kid, but since I
>got into studying physics seriously I have fallen behind on the latest
>developments in paleontology (of course, I'll be able to catch up when I
>finally build my time-machine!)..

Notoceratops bonarelli is actually quite an old discovery - a dentary from
Chubut, Argentina, named by Tapia in 1918.  The specimen is currently
missing.  Many think that this might have been from a hadrosaur.

>> similar but larger problem explaining that the sister group of
>> Archaeopteryx occur 60 million years after it. The spotty fossil record of
>> terrestrial vertebrates will always have holes like this in it.
>
>Archeopteryx's sister group are actually flightless birds, who lost the
>ability to fly before they lost their tails! Yes? No? Oh, well, it's just
>a guess :)

Actually, at least one definite dromaeosaurid (the outgroup to Archie +
Ornithurae) is known from ~130 Ma (i.e., Utahraptor) and fragments from the
Morrison Fm. which might be dromaeosaurid (or might be Archaeopteryx!) from
the same age as Archie.

Also, the sister-group to Archaeopteryx is all other birds (with
representatives from about 10-15 million years younger than Archie), while
dromaeosaurids are the sister group to Archaeopteryx + all later birds.

                                
                 Thomas R. Holtz, Jr.                  Phone: 703-648-5280      
                 Vertebrate Paleontologist         Fax:    703-648-5420
tholtz@geochange.er.usgs.gov ------------>       th81@umail.umd.edu
U.S. Geological Survey          ------------->       University of Maryland
Branch of Paleontology & Stratigraphy ---->       Department of Geology
MS 970 National Center
Reston, VA  22092               ------------->        College Park, MD  20742
                                                          U.S.A.