Volume 43 April 2008

Permanent URI for this collection

https://wiredspace.wits.ac.za/handle/10539/13289

Browse

Browsing Volume 43 April 2008 by Keyword "biostratigraphy"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    A new cynodont record from the Tropidostoma Assemblage Zone of the Beaufort Group: implications for the early evolution of cynodonts in South Africa
    (Bernard Price Institute for Palaeontological Research, University of the Witwatersrand, 2008-04) Botha-Brink, J.; Abdala, F.
    A new specimen of cynodont has been recovered from the lower Upper Permian levels of the Tropidostoma Assemblage Zone of the South African Karoo Basin. A series of characters, including the presence of an interpterygoid opening, triconodont postcanine teeth, which are circular in crown view, a probable lingual cingulum, and most significantly, the presence of a masseteric fossa high on the coronoid process, allows this specimen to be assigned to the Procynosuchidae. However, unlike most procynosuchids, precanine teeth are absent and the incisors are represented by four left and five right upper and probably, three lower teeth. Considering the small size of the new specimen from the Tropidostoma Assemblage Zone we identify it as a juvenile Procynosuchus delaharpeae, the only species currently recognized in the genus. The low number of incisors and absence of precanines in this specimen are interpreted as ontogenetic variation (i.e. juvenile characters). This discovery extends the biostratigraphic range of Procynosuchus, as it is now recorded in three assemblage zones, indicating that this taxon is the longest-lived cynodont in the Karoo Basin. The new specimen of Procynosuchus and the recently described Charassognathus gracilis, are the oldest global records of cynodonts, and indicate an earlier initial radiation of this lineage than was previously thought.
  • Thumbnail Image
    Item
    A second specimen of Blikanasaurus (Dinosauria: Sauropoda) and the biostratigraphy of the lower Elliot Formation
    (Bernard Price Institute for Palaeontological Research, university of the Witwatersrand, 2008-04) Yates, Adam M.
    A second specimen of the rare basal sauropod Blikanasaurus cromptoni, is recorded from a site in the Ladybrand district of the Eastern Free State, South Africa. The specimen consists of a right metatarsal 1 that originated from the upper 20mof the lower Elliot Formation. It can be referred to B. cromptoni on the basis of its small size and highly robust proportions, which distinguish this taxon from all other sauropodomorphs. This record extends the geographic distribution of B. cromptoni north into the region of the main Karoo Basin where the Elliot Formation is dramatically thinner. It also extends the known stratigraphic range of B. cromptoni up from the base of the Elliot Formation into a position near the top of the lower member. This new record, combined with other new discoveries, supports the hypothesis that the thin northern part of the lower Elliot Formation is a condensed section that is largely, if not entirely, coeval with the thicker southern sections.