Hi Tim,
I see there is some discussion on this taxon in the DML. Could you forward
this message to the list?
Hi all,
As Scott will no doubt report I didn't make it to the IICLPV conference.
The stuff-up occured when my travel agent told me that I did not need a
visa for Brazil, when actually I do. So I had the very unpleasant
experience of being turned away from the flight at the airport. Reading
Scott's report about how good the food and the coffee is over there is just
increasing the disapointment. Anyway given the discussion about the curious
beast 'Aliwalia' I present here the abstract of the talk I should have
presented yesterday.
SOLVING A DINOSAURIAN PUZZLE: THE IDENTITY OF ALIWALIA REX REVEALED
Adam M. Yates
Bernard Price Institute for Palaeontological Research, University of the
Witwatersrand, Private Bag 3, WITS 2050, Johannesburg, South Africa
Aliwalia rex Galton, 1985 was based on a single fragmentary femur of a
large dinosaur from the lower Elliot Formation (Norian, Late Triassic) of
South Africa. Originally it was described as a large herrerasaurian but
later workers failed to find any derived characters that could conclusively
place it closer to Herrerasauridae than to any other dinosaurs. Usually it
is simply regarded as Dinosauria incertae sedis, although the hypothesis
that it was a relatively basal taxon that was primitively carnivorous has
persisted. This hypothesis has been bolstered by the referral of an
isolated maxilla from the type locality to A. rex.
In 2003 a second Aliwalia rex femur was found in the lower Elliot
Formation by a team from Bernard Price Institute, University of
Witwatersrand. In this case the femur was associated with other postcranial
bones that show clear sauropodomorph synapomorphies. Examination of
collections at the Transvaal Museum and the Council for Geoscience in
Pretoria has shown this is not the first association of Aliwalia-type
femurs with sauropodomorph bones. Indeed one of these associations has been
named: Eucnemosaurus fortis Van Hoepen, 1920. It is clear that these
associations real and are not fortuitous taphonomic accidents. Indeed the
femurs themselves display the derived sauropodomorph synapomorphy of a
proximo-distally elongated, ridge-like lesser trochanter. Several
prosauropod grade sauropodomorphs such as Massospondylus carinatus,
Lufengosaurus huenei and Riojasaurus incertus also display the distinctive
semi-pendant fourth trochanter that has been used to diagnose Aliwalia rex.
These specimens represent a distinctive taxon of prosauropod-grade
sauropodomorph and the forgotten Eucnemosaurus fortis is its valid name.
Aliwalia rex is a junior synonym of Eucnemosaurus fortis. Amongst
sauropodomorphs E. fortis shares a large posterior tubercle on the proximal
femur with Riojasaurus incertus (a reversal to a non-dinosaurian character
state). Cladistic analysis of basal sauropodomorph relationships finds that
Riojasaurus and Eucnemosaurus are sister taxa within a large clade that
also contains Massospondylidae, Yunnanosaurus, Anchisauridae,
Melanorosauridae, Antetonitrus and traditional sauropods (Vulcanodontidae
and Eusauropoda) to the exclusion of Plateosauridae and more basal
sauropodomorphs.
cheers
Adam