. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. ANNALS OF THE SOUTH AFRICAN MUSEUM c ) V—si. Fig. 4. Schematic representation of a coronal section through the nasal bosses showing the three basic types. A. 'Type 1\ B. 'Type 2'. C. 'Type 3'. See text for explanation. Various cranial sizes, or inferred ontogenetic stages, are present for both the second and third types of nasal bosses, whilst the smallest, and presumably youngest, skulls in the present sample evince a 'Type 1' nasal boss. It is possible that the nasal bosses in Aulacephalodon could
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. ANNALS OF THE SOUTH AFRICAN MUSEUM c ) V—si. Fig. 4. Schematic representation of a coronal section through the nasal bosses showing the three basic types. A. 'Type 1\ B. 'Type 2'. C. 'Type 3'. See text for explanation. Various cranial sizes, or inferred ontogenetic stages, are present for both the second and third types of nasal bosses, whilst the smallest, and presumably youngest, skulls in the present sample evince a 'Type 1' nasal boss. It is possible that the nasal bosses in Aulacephalodon could have served as a sexually selective feature for mate recognition and/or agonistic display mechanisms, or for both. Furthermore, the several relatively large crania (specimens 19, 25-26 and 29) which show nasal bosses intermediate in form between 'Types 2 and 3' may represent the antimodal overlap of the bimodal distribution of a discontinuous feature such as sexual dimorphism. However, a number of the crania in which the nasal bosses are indeterminate are broken and poorly preserved. It is possible that those crania with the more robust, 'Type 3' nasal bosses represent the male condition. The same has been postulated obliquely by pre- vious workers (Broom 1937, 1948; Keyser 1969). In the present series, it appears that, once a certain cranial size had been reached, the nasal bosses assumed one of two rather distinct configurations (Fig. 7). It is suggested that the smaller crania, in which the nasal bosses are only slightly expressed ('Type 1'), represent relatively young, sexually immature individuals. Specimen 6 ( 300) possesses rather small nasal bosses of the 'Type 2' (female) configuration (Fig. 8). This fossil has been identified tentatively as female (Figs 6-7). It is possible that with growth the nasal bosses of both sexes were of a 'Type 2' configuration before sexual maturity (or dimorphism) had been achieved; the smallest positively identifiable male cranium
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectnaturalhistory, booky
