Aliwalia and friends

[Adam Yates <yatesa@geosciences.wits.ac.za>]

Hi everyone,

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!

Cheers

Adam