Wits Evolutionary Studies Institute (ESI)

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Author: search.filters.author.Welman, Johann

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    A new find of Trematosuchus (Amphibia, Temnospondyli) from the Cynognathus Zone of South Africa
    (Bernard Price Institute for Palaeontological Research, 1994) Shishkin, Michael A; Welman, Johann
    Some aspects of the cranial morphology of Trematosuchus sobeyi, a temnospondylous Trematosaurid amphibian from the South African Cynognathus Zone, are described in detail for the first time from a new fossil find referred to this form. The new specimen is similar in size to that of the holotype of Trematosuchus sobeyi but differs in the more moderate elongation of the snout. Apart from the presence of the septomaxilla, the validity of the genus Trematosuchus is reconfirmed inter alia by its much larger size and the position of the supraorbital sensory groove alongside the lachrymal margin rather than crossing this bone. This last characteristic differentiates Trematosuchus from all other trematosauroids. T. Sobeyi is of particular importance since it represents the only purely freshwater Gondwanan form closely comparable to the European Trematosaurus. The presence of T. Sobeyi in the lowermost strata of the Cynognathus Zone in South Africa, in association with some other forms related to the Upper Olenekian (Middle Buntsandstein) tetrapod assemblage of Europe, indicates that these strata belong to the Scythian in contrast to the higher strata of the Cynognathus Zone which are Anisian.
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    Statistical analysis of skulls of Triassic proterosuchids (Reptilia, Archosauromorpha) from South Africa
    (Bernard Price Institute for Palaeontological Research, 1993) Welman, Johann; Fleming, Alex
    Size-related differences have previously been considered to be important in distinguishing the four proterosuchian archosauromorph species described from South Africa. Previous authors hypothesized that these differences were due to allometric growth. In this study, a statistical analysis of 85 parameters measured in 12 skulls, including all the type specimens, has been carried out. The results show that all the specimens can be fitted into a growth series, supporting a hypothesis expressed by Cruickshank (1972). Variation in the growth rate of parts of the proterosuchid skull and the possible functional significance of such allometric growth patterns are investigated. On the basis of specimens measured in this study and assuming that they all belong to a single species, it would appear that the South African proterosuchids did not display a strong degree of sexual dimorphism.