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Aliwalia and friends
My hectic schedule is calming down a little bit so Iâm dropping in on the
list again for a little while. In response to a number of posts about
sauropodomorphs and Aliwalia I first want to say the correct spelling is indeed
Eucnemesaurus: the misspelling in the abstract is my fault entirely. It seems I
have very bad spelling recognition skills. It actually took a few minutes of
staring at the posts pointing out this error before I finally noticed I had put
an âoâ in place of the âeâ. Well at least it got caught before
submission of any paper!
Second. The identity of the maxilla. As people have noted it is very, very
unlikely to come from Eucnemesaurus. So what is it? Short answer is we donât
know. The big carnivorous archosaur (or archosaurs) are one of the most
frustrating aspects of the lower Elliot Fauna and I keep hoping that the next
field season will be the one to yield diagnostic remains. So far all we get are
shed teeth and scraps of jaw. Huene erected the tooth taxon Basutodon for one
of these isolated teeth and many have suggested that it is a rauisuchian. It
could well be but a large early theropod is not out of the question. There may
well be a mix of both in the assemblage. We do however know a little bit more
about a large predator from the upper Elliot so watch this space!
Third. The embryos described by Kitching in Pal. afr. Jay asked if these were
also sauropodomorph embryos like the ones in the Reisz et al. Science paper.
They certainly are because they are the same specimens! The BPI technicians
were unable to prepare the embryos out very successfully (they exposed the big
frontals and a few long bones) so Kitching wisely halted preparation before too
much damage was incurred. As a result of that far-sighted action the embryos
were in good shape when a preparator with exceptional skill and the right
equipment (in this case Diane Scott) became available. It did mean that when
Kitching first described the embryos he had too few features to work from and
was uncertain what sort of reptile they were.
Finally. Sauropodomorph phylogeny. Yes, the content of Prosauropoda seen in
Yates and Kitching 2003 and Yates 2004 is gone and the phylogeny more closely
resembles that in my earlier T. caducus paper. This is actually a robust result
and there is a slew of new data in this new analysis, including cranial data
for Melanorosaurus and a host of new characters. There are still areas of great
uncertainty, where the taxa can shift around with slight changes to the matrix
but the basic topology of Saturnalia + (Thecodontosaurus + (Plateosauridae +
(Massospondylidae + (Anchisaurus, Melanorosaurus, âtypical sauropodsâ))))
is solid. This does have big implications for phylogenetic taxonomy. I agree
that in this topology using Prosauropoda is unnecessary (especially given the
low diversity of Plateosauridae in this topology) and I prefer to use
Plateosauridae in its favour. Obviously a Massospondylidae that is a synonym of
Sauropoda is aesthetically unpleasant and I would like to modify its
current definition by simply adding another exclusive anchor taxon, namely
Saltasaurus. I think the total group usage of the name Sauropodomorpha (ie. the
sister group of Theropoda) has a lot of inertia behind it and we should stick
with it even if it doesnât have priority. The node based name Plateosauria
then becomes available for the Plateosauridae + almost everything else clade. I
also find Galton and Upchurchâs definition of Anchisauria very usefull, for
labelling the advanced sauropodomorphs. Where do we apply the name Sauropoda?
This is a thorny issue. Using the current definition with this topology it
would be the clade containing Massospondylidae, Anchisaurus, Melanorosaurus
etc. Thus the content of the clade has become bloated way beyond the original
intent of the name and I think in this case we can suppress the stem-based
definition of Sauropoda in favour of a new node based name within the
Anchisauria (say Vulcanodon + Saltasaurus, or Antetonitrus + Saltasaurus). A
new name would then be required for the lar!
ge clade that is the sister group of Plateosauridae.
Oh, David also queried my use of âMelanorosauridaeâ. I was applying the
definition in Galton and Upchurch but modifying slightly so that it doesnât
include sauropods as well, ie. Melanorosauridae includes all taxa more closely
related to Melanorosaurus than to Anchisaurus, or Saltasaurus. Camelotia may,
or may not, be a melanorosaurid, its position is quite flaky.
Finally finally: Someone else asked what was included in Massospondylidae in my
analysis. I find that only three taxa are massospondylids, namely
Massospondylus, Lufengosaurus and Coloradisaurus. However this is one of weak
areas of the tree and there are other taxa that may, or may not, eventually
turn out to be Massospondylids including Jingshanosaurus (NOT a synonym of
Yunnanosaurus I might add) and Gryponyx (yes this old taxon has been
resurrected as well, see: Vasconcelos, C. C. and Yates, A. M. 2004.
Sauropodomorph biodiversity of the upper Elliot Formation (Lower Jurassic) of
Southern Africa. Geoscience Africa 2004, Abstract volume, University of the
Witwatersrand, Johannesburg, South Africa, pp. 670.)
Finally Iâd like to add that every cloud has a silver lining and the money I
didnât spend in Brazil will pay for SVP â I hope to see many of you there!