. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. 224 ANNALS OF THE SOUTH AFRICAN MUSEUM. (b) Fig. 55. Comparison of the hypophyseal region oiLystrosaurus and a Permian dicynodont. (a) Dicynodont sp., No. 5600; (b) Lyslrosaurus sp., No. 11180. Anterodorsal views. is continued ventrally as an unossified zone, is a constant feature in Lyslrosaurus, and its shape strongly suggests that it housed a soft body of some kind. If the pit did indeed house a portion of the hypophysis, the basioccipital would have formed a dorsum sellae. Boonstra
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. 224 ANNALS OF THE SOUTH AFRICAN MUSEUM. (b) Fig. 55. Comparison of the hypophyseal region oiLystrosaurus and a Permian dicynodont. (a) Dicynodont sp., No. 5600; (b) Lyslrosaurus sp., No. 11180. Anterodorsal views. is continued ventrally as an unossified zone, is a constant feature in Lyslrosaurus, and its shape strongly suggests that it housed a soft body of some kind. If the pit did indeed house a portion of the hypophysis, the basioccipital would have formed a dorsum sellae. Boonstra (1968), however, suggested that in his sectioned Dicynodon the sella turcica (and therefore the hypophysis) was small. If this were so in Lyslro- saurus, and the hypophysis did not reach back to the basicranial pit, then the basisphenoid would have formed a floor for the body behind the internal carotid opening. In this case no distinct sella turcica was present in Lyslrosaurus. In ventral view the shortening of the skull has caused the changes in the pterygoid region illustrated in Figure 56. When the skulls of Emydops and Lyslrosaurus are brought to the same basal length, it can be seen that the choana, including the interpterygoidal fossa or vacuity of Lyslrosaurus is slightly shorter than in Emydops [Lyslrosaurus 32-6°'o of basal length, Emydops 36-7% of basal length). The chief difference between the two types in this region is, however, the structure of the interpterygoidal vacuity and the position of the parasphenoid and vomer. In the endothiodontid genera Emydops and Palemydops the posterior portion of the relatively broad median plate of the vomer is recessed into the choana and lies far above the level of the ventral pterygoidal and palatine border of the choana. The interpterygoidal vacuity is wide and extends far. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of
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