. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. EPIPTERYGOID—ALISPHENOID TRANSITION IN THERAPSIDA 417 Ictidosauria In Diarthrognathus broomi the dorsal portion of the epipterygoid is extremely broad and overlaps the prootic above the prootic incisure. Here the posterior edge of the epipterygoid is slightly indented for the maxillary and mandibular branches of the trigeminal nerve (fig. 17). Crompton (1958) states that although it is difficult to ascertain, it would appear that the quadrate ramus of the epipterygoid meets the antero-medial edge of
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. EPIPTERYGOID—ALISPHENOID TRANSITION IN THERAPSIDA 417 Ictidosauria In Diarthrognathus broomi the dorsal portion of the epipterygoid is extremely broad and overlaps the prootic above the prootic incisure. Here the posterior edge of the epipterygoid is slightly indented for the maxillary and mandibular branches of the trigeminal nerve (fig. 17). Crompton (1958) states that although it is difficult to ascertain, it would appear that the quadrate ramus of the epipterygoid meets the antero-medial edge of the quadrate. The quadrate is much reduced, S-shaped in occipital view, and the articular surface is markedly concave. This latter feature, according to Crompton, is of great significance as in all known therapsids, including Bienotherium and Oligokyphus, the articular face of the quadrate is either flat or convex, but never concave. It is also significant that the mammalian malleus (articular) possesses a convex articular surface which meets a convex articular face in the incus (quadrate). In Bienotherium (Hopson, 1964) the epipterygoid and the anterior part of the prootic together form the side wall of the brain case (fig. 18). The quadrate ramus of the epipterygoid is more vertically orientated and deeper than in EPIPTERYGOID PARIETAL PROOTIC. Fig. 18. Bienotherium yunnenense. Lateral view of braincase reconstructed from serial sections. (After Hopson, 1964.). 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 : The Museum
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectnaturalhistory, booky
