Wits Evolutionary Studies Institute (ESI)
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Item 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.Item Taxonomy of the Triassic anomodont genus Kannemeyeria(Bernard Price Institute for Palaeontological Research, 1970) Cruickshank, A. R. I.The types of the species hitherto assigned to the genus Kannemeyeria Seeley 1908 have been re-examined and D. simocephalus Weithofer, D. latifrons Broom, K. proboscoides Seeley, Sagecephalus pachychynchus Jaekel and K. erithrea Haughton are synonymised as K. simocephalus (Weit). K. wilsoni Broom is retained as a monotypic species, but could be considered a female of K. simocephalus. The genus Kannemeyeria is redefined using the type of K. erithrea as a basis, as this specimen is complete, almost undistorted and comes from a reliably recorded locality, unlike the majority of other types. Kannemeyeria vanhoepeni Camp, while closely related to Kannemeyeria Simocephalus, has only one character in common with that species and is placed therefore in a new genus Proplacerias. This name is chosen because the specimen seem to have the characters which might be expected in a very early representative of the line leading to Placerias. K. argentinensis Bonaparte and K. latirostris Crozier are retained for valid reasons as separate species, occurring as they do in South America and Zambia respectively.Item THE MODE OF LIFE OF GORGONOPSIANS(BERNARD PRICE INSTITUTE FOR PALAEONTOLOGICAL RESEARCH, 1973) Cruickshank, A. R. I.The gorgonopsians as typically developed were undoubtedly the dominant land carnivores of the Upper Permian and have been compared with the sabre-tooth cats of the Tertiary (Parrington, 1955, p. 7 and Kemp, 1969b, p. 321). However, the similarities between the two groups are almost entirely confined to their dentitions and the general proportions of their lower jaws, both possessing greatly enlarged canine teeth and relatively weak coronoid processes on the lower jaw. In addition, both groups show adaptations to allow the lower jaw to make a wide gape, thus allowing the upper and lower canines to clear each other when the jaw is opened and, at the same time, keeping the jaw articulations from dislocating during this movement.Item TAXONOMY OF THE TRIASSIC ANOMODONT GENUS KANNEMEYERIA(BERNARD PRICE INSTITUTE FOR PALAEONTOLOGICAL RESEARCH, 1970) Cruickshank, A. R. I.The types of the species hitherto assigned to the genus Kannemeyeria Seeley 1908 have been re-examined and D. simocephalus Weithofer, D. latifrons Broom, K. proboscoides Seeley, Sagecephalus pachychynchus Jaekel and K. erithrea Haughton are synonymised as K. simocephalus (Weit). K. wilsoni Broom is retained as a monotyplc species, but could be considered a female of K. simocephalus. The genus Kannemeyeria is redefined using the type of K. erithrea as a basis, as this specimen is complete, almost undistorted and comes from a reliably recorded locality, unlike the majority of other types. Kannemeyeria vanhoepeni Camp, while closely related to Kannemeyerza Simocephalus, has only one character in common with that species and is placed therefore in a new genus Proplacerias. This name is chosen because the specimen seems to have the characters which might be expected in a very early representative of the line leading to Placerias. K. argentinensis Bonaparte and K. latirostris Crozier are retained for valid reasons as separate species, occurring as they do in South America and Zambia respectively.Item TOOTH STRUCTURE IN Rhizodus hibberti AG., A RHIPIDISTIAN FISH(BERNARD PRICE INSTITUTE FOR PALAEONTOLOGICAL RESEARCH, 1968) Cruickshank, A. R. I.The structure of the large laniary teeth of the Lower Carboniferous rhipidistian fish Rhizodu hibberti Ag. is interpreted in terms of a new theory of tooth development. The structure of these teeth is found to correspond almost exactly to that of the synchronomorial scale as defined by Orvig (1951) and Stensio (1961; 1962). These labyrinthodont teeth are thus shown to be composed of many tooth primordia, and are not a single unit of dentine. Some isolated Rhizodus teeth are described in which the entire labyrinthodont structure is missing, leaving an empty space inside the tooth. From this, a non-mechanical tooth removal mechanism is postulated.Item A COMPARISON OF THE PALATES OF PERMIAN AND TRIASSIC DICYNODONTS(BERNARD PRICE INSTITUTE FOR PALAEONTOLOGICAL RESEARCH, 1968) Cruickshank, A. R. I.Whilst comparing the skulls of some Triassic dicynodonts with Permian members of the family, it was noted that the interpterygoid space in the former is consistently smaller than in the latter (Cruickshank 1965: 1967). In analysing this difference further, the palates of a series of Permian and Triassic dicynodonts were examined, either directly or from published diagrams. From graphs drawn using the various measurements taken from the palates, the geological age of the specimens can be deduced as can their estimated lengths, if fragmentary.