Browsing by Author "Firm, Lyndsey"
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- ItemA comparative study of the morphology of the braincase and associated structures of early Therocephalia (Amniota: therapsida)(Stellenbosch : Stellenbosch University, 1994) Firm, Lyndsey; Van den Heever, J. A.; Stellenbosch University. Faculty of Science. Department of Botany and Zoology.ENGLISH ABSTRACT: The early Therocephalia lies at the base of the line of mammal-like reptiles which eventually gave rise to mammals. The phylogenetic position of this taxon is therefore of great value in establishing mammalian ancestry and the description of the braincase forms a vital part of this research. However, a valid description of the early therocephalian braincase is still lacking. The aim of this study is to describe the braincase of the early Therocephalia in an effort to fill this hiatus and provide additional morphological information which may be utilized in future phylogenetical analysis. The primary study is based on serial sections of Glanosuchus macrops. This study was aided by reconstructions produced firstly, by means of two computer programs, secondly Pusey's reconstruction techniques and thirdly, building a wax model. These techniques, except for the grinding of the fossil, constitute the practical part of this study. The constituent bones of the braincase are individually described, with emphasis on the internal structure and foramina. The internal structure of the braincase is then discussed completely, especially the structure of the inner ear, and compared to other relevant therapsid groups. A postulate concerning the shape of the early therocephalian brain, based on a cranial cast derived from the serial sections is presented. Possible activity rates and metabolic tempo are deduced from the proposed structure of the brain. Keywords: Early therocephalian, braincase, inner ear, brain reconstruction.