Volume 52 2017–2018

Permanent URI for this collectionhttps://wiredspace.wits.ac.za/handle/10539/23007

Browse

Subject: search.filters.subject.Therapsida

Search Results

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    The first skeletal evidence of a dicynodont from the lower Elliot Formation of South Africa
    (Evolutionary Studies Institute, 2018) Kammerer, Christian F.
    Historical fossil specimens from the lower Elliot Formation are identified as representing a large-bodied dicynodont, the first known from skeletal material in the Late Triassic of South Africa. Although fragmentary, these fossils differ from all other known Triassic dicynodonts and are here described as a new taxon, Pentasaurus goggai gen. et sp. nov. Pentasaurus can be distinguished from other Triassic dicynodonts by a number of mandibular characters, most importantly the well-developed, unusually anteriorly-positioned lateral dentary shelf. Phylogenetic analysis indicates that Pentasaurus is a placeriine stahleckeriid. Placeriines include the latestsurviving dicynodonts but their remains are primarily known from the Northern Hemisphere, with their only previously-known Southern Hemisphere representative being the Middle Triassic Zambian taxon Zambiasaurus. The discovery of a placeriine in the Late Triassic of SouthAfrica supports recent proposals that local climatic conditions, not broad-scale biogeographic patterns, best explain the observed distribution of Triassic tetrapods. The tetrapod fauna of the lower Elliot Formation is highly unusual among Triassic assemblages in combining ‘relictual’ taxa like dicynodonts and gomphodont cynodonts with abundant, diverse sauropodomorph dinosaurs.
  • Thumbnail Image
    Item
    Rediscovery of the holotype of Clelandina major Broom, 1948 (Gorgonopsia: Rubidgeinae) with implications for the identity of this species
    (Evolutionary Studies Institute, 2017-12) Kammerer, Christian F.
    No specimen number was given for the holotype of the rubidgeine gorgonopsian species Clelandina major Broom, 1948 in its original description. Historically, a specimen in the Rubidge Collection (RC 94) was considered to represent Broom’s type specimen for C. major. However, recent study has revealed that the holotype of C. major is in fact a different specimen in the McGregor Museum in Kimberley (MMK 5031). The morphology of this specimen is consistent with the genus Clelandina, contra work based on RC 94 that considered C. major referable toAelurognathus. Clelandina major is here considered synonymous with the type species Clelandina rubidgei.MMK5031 represents only the fifth known specimen of this rare and unusual gorgonopsian.
  • Thumbnail Image
    Item
    The bony labyrinth of late Permian Biarmosuchia: palaeobiology and diversity in non-mammalian Therapsida
    (2017-07) Benoit, Julien; Manger, Paul R; Fernandez, Vincent; Rubidge, Bruce S
    Biarmosuchia, as the basalmost group of Therapsida (the stem group of mammals), are important for understanding mammalian origins and evolution. Unlike other therapsid groups, the bony labyrinth of biarmosuchians has not yet been studied, despite insightful clues that bony labyrinth morphology can provide to address palaeobiology and phylogeny of extinct animals. Here, using CT scanning, surface reconstruction and a 3D geometric-morphometric protocol of 60 semi-landmarks on the bony labyrinth of 30 therapsids (including three Mammaliaformes), it is demonstrated that bony labyrinth morphology of biarmosuchians is very distinctive compared to that of other therapsids. Despite the primitive nature of their cranial morphology, biarmosuchians display highly derived traits in the structure of the bony labyrinth. The most noticeable are the presence of a long and slender canal linking the vestibule to the fenestra vestibuli, an enlarged and dorsally expanded anterior canal, and the absence of a secondary common crus (except for one specimen), which sets them apart from other non-mammalian therapsids. These characters provide additional support for the monophyly of Biarmosuchia, the most recently recognized major therapsid subclade. Although implications of the derived morphology of the biarmosuchian bony labyrinth are discussed, definitive interpretations are dependent on the discovery of well-preserved postcranial material. It nevertheless sheds light on a previously overlooked diversity of bony labyrinth morphology in non-mammalian therapsids.