Volume 21 1978

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    Palaeontologia africana Volume 21
    (Bernard Price Institute for Palaeontological Research, 1978)
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    Trackways in the Stormberg
    (Bernard Price Institute for Palaeontological Research, 1978) van Dijk, D. E.
    Vertebrate trackways in the lower groups of the Karoo Supergroup are mainly pre- Beaufort fish trails, although some tetrapod trackways are known (Griffiths, 1963, p. 292; plate I; specimens in the South African Museum). Recently fish trails have been discovered in the Beaufort, for instance at Kilburn and Wagondrift, but the Beaufort, despite its rich amphibian, reptilian and synapsid fauna, is remarkable for the paucity of its vertebrate trackways. Of the Stormberg (of Lesotho) it was early noted "Fossils are comparatively rare, but reptile tracks are fairly abundant"
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    Atmospheric carbon dioxide/oxygen imbalance in the late Cretaceous, hatching of eggs and the extinction of biota
    (Bernard Price Institute for Palaeontological Research, 1978) Oelofsen, B. W.
    A new theory explains why dinosaurs, pterosaurs and large avian species like Hesperornis became extinct at the end of the Cretaceous while mammals, smaller Cretaceous birds, crocodiles, chelonians and saurians survived . An atmospheric carbon dioxide/oxygen imbalance at the end of the Cretaceous caused by kimberlite volcanism, basalt flows and a reduction in oxygen production by marine phytoplankton is proposed. The unfavourable area to volume ratio of large eggs for diffusion of respiratory gases compared to that of small eggs resulted in the asphyxiation of the embryos of large endothermic egg laying groups. Endothermic species, e.g. dinosaurs that covered their eggs with soil, restricted the free circulation of air and would have been first to become extinct. Smaller ectothermic species, e.g. crocodiles, chelonians and saurians with lower embryonic respiratory requirements and endothermic species like the birds that did not cover their eggs, survived.
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    The stratigraphic distribution and occurrence of South African fossil Amphibia in the Beaufort beds
    (Bernard Price Institute for Palaeontological Research, 1978) Kitching, J. W.
    A short account is given of the distribution and occurrence of fossil amphibians from the Beaufort succession, based on analyses of specimens in various South African and overseas institutions. Their occurrence is based on the re-examination of all the localities which have yielded amphibian remains to date and on field observations during the course of collecting. Attention is drawn to the paucity of fossil amphibians throughout the Beaufort palaeontological record. Possible causes of this paucity are discussed.
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    A new bauriamorph from the Omingonde Formation (Middle Triassic) of South West Africa
    (Bernard Price Institute for Palaeontological Research, 1978) Keyser, A. W.
    A new genus and species of bauriamorph therapsid from the Anisian Omingonde Formation (Middle Triassic) of South West Africa is described as Herpetogale marsupialis gen. et sp. nov. This new form is chronologically the latest known member of the therocephalian lineage. It is in many ways more advanced than Bauria, but it also displays a number of more primitive features . It is advanced in its reduced postcanine series, slightly larger secondary palate, smaller suborbital fossae, and more pronounced coronoid processes of the dentaries, displaying laterally very distinct fossae maJsetericae. A very distinct crista IacialiJ is developed in front of the orbit. Primitive features are the presence of a pineal foramen and complete postorbital bars. Conspicuous and no doubt specialised are the pronounced "cheek cavities" well demarcated above by maxillary overhangs and below by shelf-like expansions on the dentaries. This arrangement suggests "cheek pouches" for food storage reminiscent of a habit in modem primates and certain rodents. The skull is complete, very little distorted or damaged, with lower jaw in occlusion. Besides an account of the cranial morphology, attention is also given to jaw musculature and the taxonomic position of the Bauriamorpha.