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Re: New Sauropod
Dann Pigdon wrote:
Certainly by the EK, Australian dinosaur diversity appears more like
that of Asia than India or South America.
I read this and thought, "Hmmm.... Does Dann know something I don't know?"
:-)
Dann probably knows more about me than I do on this topic, but to me Aussie
dino diversity in the early-middle Cretaceous doesn't seem to show any more
affinity to Asia than to any other part of the world. To begin with, the
sauropods are all titanosauriforms and resemble the contemporary (or
near-contemporary) titanosauriforms found anywhere else in the world. So
far, five titanosauriorm taxa are known, comprising basal titanosaurs
(including _Austrosaurus_) and one possible brachiosaurid. (That's based
on the assessment of Molnar [2005]).
The Aussie theropods from this time comprise putative abelisaurs (_Kakuru_,
like the earlier _Ozraptor_), carnosaurs (indet.; this is the
_Fukuiraptor_-like astragalus), oviraptorosaurs (indet.), alvarezsaurs
(_Rapator_), dromaeosaurs (indet.), birds (_Nanantius_ and some indet.
stuff), and critters that are hard to classify (e.g., _Timimus_).
Aussie ornithischians include a bevy of small cursorial euornithopods
(_Fulgurotherium_, _Atlascopcosaurus_, _Leallynasaura_, _Qantassaurus_), the
big euornithopod _Muttaburrasaurus_, the ankylosaur _Minmi_, and a
_Leptoceratops_-like ulna (_Serendipaceratops_). Some of the Aussie
ornithopods may represent an endemic lineage and/or be related to the
rhabdodontids of Europe. Every ankylosaur phylogeny has _Minmi_ coming up
in a different part of the tree; but in any case, little _Minmi_ shows no
especially close kinship to any other known ankylosaur.
Of course, the word
'diversity' should probably never be used in the same sentence as
'dinosaur' and 'Australia", as far as fossil finds go. :)
If only these Aussie dinosaurs took more care to leave more of their bodies
behind! Most are known from tantalizing bits and pieces (as do the
non-dinosaurs, like that peculiar dicynodont). For example, I'd love to see
what the rest of _Rapator_ looked like; or what those oviraptorosaur
elements came from. Quite a lot of phylogenetic diversity seems to be
represented in early-mid Cretaceous Australia - but for a continent of its
size, the total yield of dino remains is less than spectacular. Not for
lack of trying on the part of paleontologists...
K and T Dykes <ktdykes@arcor.de> wrote:
"Adherent matrix, a yellow-brownish mudstone, betrays their most likely
source as the Allaru Formation, a thick (ca. 250 m) succession of mudstones
and siltstones which outcrop exstensively in the region of Alderley..."
This is the horizon that yielded the type specimen of _Austrosaurus_.
The best explanation presently available is
that these fragments come from a Lower Cretaceous dicynodont. While that
sounds outrageously unlikely, they couldn't come up with a more plausible
conclsion. And the authors certainly appear to have tried all options.
Some years ago, Fox &co reported a non-mammal cynodont from the Paleocene of
Canada - _Chronoperates_ I think it was called. But I've been told that
there is some controversy over its position (i.e., whether or not it really
lies outside the Mammalia).
Cheers
Tim