. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. 180 ANNALS OF THE SOUTH AFRICAN MUSEUM. I Fig. 9. Lateral view of a large Aulacephalodon skull showing the thickening of the squamosal at the anterior end of the zygomatic arch. Specimen no. 17, 493. Scale in cm. 1977) range. There is no horizontal separation by either size or nasal boss morphology of the specimens; furthermore, two specimens (4 and 17) from the same site (Fig. 10R, Table 6) show considerable difference in both size and nasal boss configuration. One ( 1207) is a small
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. 180 ANNALS OF THE SOUTH AFRICAN MUSEUM. I Fig. 9. Lateral view of a large Aulacephalodon skull showing the thickening of the squamosal at the anterior end of the zygomatic arch. Specimen no. 17, 493. Scale in cm. 1977) range. There is no horizontal separation by either size or nasal boss morphology of the specimens; furthermore, two specimens (4 and 17) from the same site (Fig. 10R, Table 6) show considerable difference in both size and nasal boss configuration. One ( 1207) is a small individual with only minimal nasal boss development, whilst the other specimen ( 493) represents the largest skull, in the sample and it posseses well-developed 'Type 3' nasal protuberances. Specimens which show variously Type 2 and 3 nasal bosses have been recovered from at least one other locality (Fig. 101, Table 6). The facts that specimens of various sizes with different nasal boss con- figurations have been recovered from single localities, and that there is no ! geographic or stratigraphic separation of specimens evincing different sizes and . shapes, appear to support the hypothesis that the Aulacephalodon specimens studied here do, indeed, represent an ontogenetic growth series of a single species which evinced sexual dimorphism. DISCUSSION During the deposition of the Cistecephalus Zone sediments the terrain ; appears to have been characterized by broad, low gradient floodplains traversed by numerous, intermittent streams (Keyser 1970). The climate throughout this time, as inferred from the abundance of calcareous concretions and of 'desert roses', composed of pseudomorphs of calcite after gypsum (Keyser i 1966), may have been sufficiently dry to warrant the term arid. The flora of the lower Beaufort seems to lack variety, the most commonly occurring plants being the equisetaleans, Schizoneura and Phyllotheca (Keyser 1970). Both Keyser (1969, 1970) and Kitching
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectnaturalhistory, booky
