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.
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    Palaeoenvironmental models in the Eastern Karoo Basin
    (Bernard Price Institute for Palaeontological Research, 1978) Hobday, D. K.
    Palaeoenvironmental models are based on a three-dimensional conception of sedimentary rock units and their internal geometry. These models are process-oriented and are interpreted by comparison of their attributes with those of modern sedimentary environments. Six models are proposed as a result of observations in the eastern Karoo Basin, three in the Ecca and three in the Beaufort, although some are common to both. Both regressive delta and beach models are upward-coarsening, but they are readily distinguished on the basis of sandstone composition, texture and sedimentary structures. Beaches probably developed along a non-tidal or micro-tidal coast, but in most areas the relatively rapid sediment influx favoured the formation of deltas which prograded across the shallow shelf. Incised into the delta front sandstones are channels of distributary and alluvial origin. Large fluvial channels were generally meandering, and their deposits record a vertical reduction in flow energy from thalweg through point bar to levee, with the capping coal seams representing an hiatus in detrital sedimentation. Delta front sandstones within the Beaufort Group resemble superficially those of the Ecca, but display differences in vertical sequence which are tentatively ascribed to changes in density of the basin waters. Whereas the northern and eastern basin margins were characterized by persistent, moderate energy fluvio-deltaic sedimentation, with small prograding lobes separated by shallow embayments subject to crevasse splays, the southern part of the basin was the locus of major fluvial deposition as a consequence of orogenic uplift to the south. High energy braided stream conglomerates and sandstones were deposited contemporaneously with finer-grained meanderbelt and floodplain sediments, which accumulated farther basinward in an area of reduced gradient and more constant discharge. The value of these models is that most outcrops in the study area can be explained in terms of their relationship to one or more of the models. Future palaeoenvironmental synthesis should incorporate the great variety of biological information available from the Karoo Basin.
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    Allometric growth in the Diademodontinae (Reptilia; Therapsida); a preliminary report
    (Bernard Price Institute for Palaeontological Research, 1978) Grine, F. E.; Hahn, B. D.
    The hypothesis that many, if not all, of the South African and Zambian specimens, which have been regarded as different diademodontine genera and species, actually consitute a taxonomically homogeneous, ontogenetic growth series is tested. The principles of allometric growth were applied to this sample of fossils, which varied considerably in size and shape. The approach which was followed was exclusively morphometric. The results indicate that these specimens do represent various ontogenetic stages of a growth series of only a single species of Diademodon Seeley.
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    Notes on a specimen of Diademodon previously referred to Cyclogomphodon
    (Bernard Price Institute for Palaeontological Research, 1978) Grine, F. E.
    The anterior portion of the cranium of a medium-sized cynodont is described. The specimen was previously described briefly by Brink and Kitching (1953 ), who assigned it to the genus Cyclogomphodon Broom, and it was upon this specimen that they based their rediagnosis of that genus. The detailed study of this specimen has revealed that the supposed features which they considered to be generically distinctive for Cyclogomphodon either do not exist or that their validity falls away when this specimen is considered, in an ontogenetic context, as a not yet fully grown individual. It is concluded that this fossil represents a medium-sized, "juvenile", individual of Diademodon
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    The advent of herbivory in certain reptilian lineages during the Triassic
    (Bernard Price Institute for Palaeontological Research, 1978) Gow, C. E.
    The dentitions of several presumed herbivorous Triassic reptiles are described and discussed. Some changes in dentitions with growth suggest that juveniles were insectivorous. The appearance of these forms may have been facilitated by floral changes which took place in the early Triassic.
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    Aspects of palynology in Rhodesia
    (Bernard Price Institute for Palaeontological Research, 1978) Falcon, Rosemary M. S.
    This paper is based on a Doctoral Thesis presented to the University of the Witwatersrand, which in whole or part will be published elsewhere at greater length. The essence of the research is presented in three text figures which show the proposed correlations of Karoo strata on opposite sides of the Rhodesian palaeowatershed, correlations with Karoo-equivalent strata in other parts of Gondwanaland, and palaeofloristic trends in Rhodesia during the Permo-Triassic.
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    Feeding adaptations in Triassic Dicynodonts
    (Bernard Price Institute for Palaeontological Research, 1978) Cruickshank, A. R. I.
    The Dicynodontia declined markedly at the close of the Permian, entered the Triassic with very few species and had a final burst of evolutionary success in the Middle Triassic, before being overcome by archosaurian competitors in the Upper Triassic. The structure of their skull is analysed in terms of life habit and it is concluded that in all probability the most likely close analogues to the Triassic Dicynodontia were the ground sloths of the American Neogene. Browsing and grazing modes of life are recognised. It is also postulated that tusks in the Triassic Dicynodontia were used for display purposes, and that tuskless forms were either nocturnal, or lived in thick undergrowth.
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    Three capitosaurs from the Triassic of South Africa: Parotosuchus africanus (Broom 1909); Kestrosaurus dreyeri Haughton 1925, and Parotosuchus dirus sp. Nov.
    (Bernard Price Institute for Palaeontological Research, 1978) Chernin, Sharon
    Two members of the family Capitosauridae are redescribed after further preparation, namely Paratosuchus africanus (Broom 1909) and Kestrasaurus dreyeri Haughton, 1925. New material consisting of a fragmental, lower jaw or a very large parotosaur from the Cynognathus zone of Aliwal North is described, upon which a new species, Parotosuchus dirus, is erected. Paratosuchus africanus (Broom 1909) from the Cynognathus zone of Vaalbank, Albert, Cape Province, is redescribed and figured for the first time. It consists of most of the postorbital regions of the skull associated with part or the left lower jaw which are fairly well preserved and capable of being directly compared with the same parts of other taxa. Thus it is reconfirmed a valid member of the family Capitosauridae. Kestrosaurul dreyeri is re-examined and found to consist of large areas of plaster of Paris in which the original bone has been embedded. The entire skull could be about 5 cm shorter than the original reconstruction. The position and shape of the orbits are not preserved and the reconstructed lateral position found in the specimen is arbitrary. The parietal foramen is also not preserved. The nature of the preserved palate and occipital area indicates that the material probably represents a primitive member of the family Capitosauridae, not only stratrigraphically ( Lystrosaurus zone), but also morphologically. The taxonomic designation established by Welles and Cosgriff (1965) is retained. Kestrosaurus remains an enigma because it also displays certain trematosaurid characters. A partial capitosaurid jaw from the Cynognathus zone of Aliwal North, Cape Province, is also described which when reconstructed represents one of the largest amphibians found in Southern Africa. Comparisons are made with Parotosuchus pronus (Howie 1970) and Parotosuchus megarhinus (Chernin and Cosgriff 1975), which share a few similar characteristics. It is suggested that the amphibian represented by this jaw may be ancestral to both P. pronus and P. megarhinus. Based on substantial morphological differences in the symphysial and articular regions between this jaw and those of the above-mentioned parotosaurs, it is hereby proposed to erect a new species, Paratosuchus dirus (dirus = Latin: fearful), for this material.
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    Permo-triassic "lizards" from the Karoo System. Part II: A gliding reptile from the upper Permian of Madagascar
    (Bernard Price Institute for Palaeontological Research, 1977) Carroll, Robert L.
    Daedalosaurus madagascariensis, gen. et sp. nov. from the Upper Permian of Madagascar is a small reptile in which the trunk ribs are greatly elongated to support a gliding "membrane" similar to those in the Upper Triassic lizards Kuehneosaurus and lcarosaurus, and the living agamid Draco. The membrane is supported by 21 pairs of ribs compared with five to seven in Draco, ten in lcarosaurus and 11 in Kuehneosaurus. The total body mass is estimated as 250 grams, the area of the membrane nearly 200 cm2, with a wing loading of approximately 1,25 g/cm2. A second species in the fauna, belonging to the same family, Coelurosauravus elivensis Piveteau, has a very similar appendicular skeleton, but ribs of normal proportions. The maxillary dentition of Coelurosauravus is acrodont, that of Daedalosaurus pleurodont. In neither genus is the temporal region of the skull adequately known, although the configuration of the jugal in Daedalosaurus suggests that the lower temporal bar may be reduced. The primitive nature of the appendicular skeleton, with little evidence or the specializations seen in contemporary lizards, suggests that these genera should not be classified among the Squamata, but among the Eosuchia.
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    The biostratigraphy of the Permian and the Triassic. Part 5: A review of the classification and distribution of Permo-Triassic tetrapods
    (Bernard Price Institute for Palaeontological Research, 1977)
    A tabulated synthesis of the classification, with geographic and stratigraphic ranges, of the Permo-Triassic tetrapod genera (amphibians, reptiles and mammals) is presented. 657 named genera placed in 161 families are in current use. The degree of stability of these genera and the extent to which they represent a reasonable sample of the preserved remains is considered. A correlation chart of the 148 known faunas has been prepared, on the basis of which a composite zonation scheme is proposed (17 Permian and 20 Triassic zones). The concept of tetrapod "Empires" is introduced. Six successive lowland "Empires" and five concurrent aquatic "Empires" (or provinces) are recognised, recorded and briefly discussed.
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    The Umfolozia arthropod trackways in the Permian Dwyka and Ecca Groups of South Africa
    (Bernard Price Institute for Palaeontological Research, 1977) Anderson, Ann M.
    Umfolozia trackways are widespread in the glacial Dwyka and in the overlying non-glacial Ecca deposits. Populations from ten localities have been numerically analysed. A consistent, significant difference is found between the inclination of the footprints in the trackways from glacial and non,glacial localities. On the strength of this, two species are distinguished. The trackmakers living in the non-glacial environments also tended to be relatively longer than those living in the glacial environments, but there was apparently no corresponding increase in functional leg length. This resulted in a change in the proportions of the trackways. The evolution of this change suggests that the glacial deposits in Natal are younger than those in southern South West Africa and in the Cape.
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    Podozamites and associated cones and scales from the upper Triassic Molteno Formation, Karoo Basin, South Africa
    (Bernard Price Institute for Palaeontological Research, 1977) Anderson, Heidi M.
    The leaves Podozamites elongatus (Morris) Feistmantel from 24 localities, the cones Telemachus elongatus gen. et sp. nov. from nine localities and the scales Dordrechtites elongatus gen. et sp. nov. from seven localities are described from the Molteno Formation, Upper Triassic (Carnian), Karoo Basin, South Africa. On the basis of the close association of the leaves, cones and scales from certain localities it is probable that all three are derived from the same parent species belonging to the Coniferales.