A definite prosauropod dinosaur from the Lower Elliot Formation (Norian: Upper Triassic) of South Africa Adam M. Yates Bernard Price Institute for Palaeontological Research, School of Geosciences, University of the Witwatersrand, Johannesburg, Private Bag 3, WITS, 2050 South Africa. E-mail: yatesa@geosciences.wits.ac.za Received 3 June 2003. Accepted 10 September 2003 INTRODUCTION Prosauropod dinosaurs in the broad sense, that is any basal sauropodomorph that is not a member of the de- rived, columnar-limbed sauropod clade (i.e. Vulcanodon + Eusauropoda), have long been known from the Lower Elliot Formation (Upper Triassic, Karoo Supergroup) of South Africa. Indeed, the unit contains a moderate diver- sity of such dinosaurs, with three taxa, Euskelosaurus browni, Melanorosaurus readi and Blikanasaurus cromptoni, commonly being accepted as valid (e.g. Galton 1990). Another taxon, Antetonitrus ingenipes, has recently been added to the list but this was explicitly described as a basal sauropod, rather than a prosauropod (Yates & Kitching 2003). The previous three taxa are frequently referred to the Prosauropoda but recent phylogenetic work (Yates 2003, in press; Yates & Kitching 2003) suggests that none of them can be confidently placed in the Prosauropoda sensu stricto (i.e. the clade containing all sauropodomorphs that share a more recent common ancestor with Plateosaurus than with the sauropod Saltasaurus; Sereno 1998). The phylogenetic position of each of these taxa is briefly dis- cussed below before the presence of true prosauropods in the Lower Elliot Formation is examined. Euskelosaurus browni Huxley, 1866 Euskelosaurus browni is based on some fragmentary postcranial remains (BMNH R1625) of which a proximal right femur is most informative. It has been distinguished from Melanorosaurus readi on the basis of its sinuous femoral shaft, the placement of the lesser trochanter well away from the lateral margin of the femur in anterior view and the proximally placed fourth trochanter (Galton 1985). These are plesiomorphic features within Sauro- podomorpha and there are at least two different taxa in the Lower Elliot Formation that display them. In addition, the holotype does not display any synapomorphies that would allow it to be identified as either prosauropod, basal sauropod or basal sauropodomorph. Consequently the name should be discarded as a nomen dubium. The name Plateosauravus cullingworthi (Haughton, 1924) becomes the next available species name for the diagnos- tic material (SAM 3341–3356, 3602–3603, 3607–3609) that was referred to Euskelosaurus browni by Van Heerden (1979). This species was originally described as a new species of Plateosaurus but Huene (1932) erected the new genus Plateosauravus to accommodate it. Plateosauravus cullingworthi does not display any obvious, unique autapomorphies but can be diagnosed by an unusual combination of characters not found in any other sauropodomorph. These include: moderately large size (femur length of at least 545 mm); anterior dorsal neural spines with distal, lateral swellings; tall posterior dorsal neural spines reaching a height that is more than twice the length of their base; a relatively slender humerus where the width of the distal end is less than one third of the total length of the bone; a strongly sinuous deltopectoral crest that is only 42% of the length of the humerus; the postacetabular process of the ilium is square-ended; the ischial peduncle of the ilium has a posterior ‘heel’; a femur that is sinuous in both lateral and anterior views; the fourth trochanter located entirely in the proximal half of the femur and placed centrally on the posterior surface of the femur, well away from the medial edge; the descending process of the distal tibia extends as far laterally as the anterolateral process. Unfortunately, the specimens of P.cullingworthi lack the critical anatomical re- gions that are rich in useful characters (e.g. the skull and manus). Consequently, it cannot be placed with any certainty in the Prosauropoda, Sauropoda, or in a position basal to these two. A cladistic analysis by the author (Yates 2003) has found weak support for this taxon (called ‘Euskelosaurus’ in that analysis) as a basal sauropod, based largely on its tall dorsal neural spines (greater than 1.5 times the length of the base) and the reduced deltopectoral ISSN 0078-8554 Palaeont. afr. (December 2003) 39: 63–68 63 A new sauropodomorph dinosaur specimen is described and identified as a prosauropod. It is tentatively placed as the sister taxon of Riojasaurus incertus from Argentina. The systematic position of all commonly accepted sauropodomorph dinosaurs from the Lower Elliott Formation of South Africa is reviewed and it is found that none can be positively identified as prosauropod. Euskelosaurus browni is a nomen dubium based on material that cannot be identified further than Sauropodomorpha. Blikanasaurus cromptoni and Antetonitrus ingenipes are basal sauropods. Melanorosaurus readi is probably another basal sauropod but opinion remains divided. Plateosauravus cullingworthi presents conflicting character data and at present is classified as Sauropodomorpha incertae sedis. Consequently the specimen described here represents the only prosauropod specimen currently recognized in the Lower Elliot Formation of South Africa. Keywords: Triassic, Lower Elliot Formation, South Africa, Sauropodomorpha, Prosauropoda.