. Annals of the South African Museum. Annale van die Suid-Afrikaanse Museum. EPIPTERYGOID — ALISPHENOID TRANSITION IN THERAPSIDA 413 for Pristerodon. However, the general tendency within the group is for the bar, linking the epipterygoid to the quadrate portion, to become reduced; an evolutionary trend, as will be shown later, that was present also in the line that culminated in modern reptiles. Gorgonopsia In all known Gorgonopsia the epipterygoid is high and relatively narrow, with a well-developed footplate. In 'Lycaenodorf (fig. 12), Scymnognathus, Lepto- trachelus, Cynariops (Boonstra, 19
. Annals of the South African Museum. Annale van die Suid-Afrikaanse Museum. EPIPTERYGOID — ALISPHENOID TRANSITION IN THERAPSIDA 413 for Pristerodon. However, the general tendency within the group is for the bar, linking the epipterygoid to the quadrate portion, to become reduced; an evolutionary trend, as will be shown later, that was present also in the line that culminated in modern reptiles. Gorgonopsia In all known Gorgonopsia the epipterygoid is high and relatively narrow, with a well-developed footplate. In 'Lycaenodorf (fig. 12), Scymnognathus, Lepto- trachelus, Cynariops (Boonstra, 1934a) and Aelurognathus (Haughton, 1924), the footplate has a long tapering anterior extension, with a short posterior extension ending some distance away from the quadrate. Boonstra found no evidence in this group of a widening of the vertical portion of the epipterygoid. EPIPTERYGOID. Fig. 12. ''Lycaenodon\ Lateral view of skull with dermal bones cut away. (After Boonstra, 1934a.) Therocephalia In the early Tapinocephalus Zone forms such as the pristerognathids Scylacosaurus and Scymnosaurus (Boonstra, 1934b, 1954), and most of the primitive therocephalians, the vertical portion of the epipterygoid is still relatively narrow, but in Glanosuchus macrops (Boonstra, 1954) the epipterygoid has become dumb-bell-shaped, although still not much widened. The base has no noteworthy posterior process. However, in the lycosuchid Trochosaurus major (Boonstra, 1934b) occurring in the same zone, the epipterygoid has. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original South African Museum. Cape Town [etc. ] The Museu
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