Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum . PMX. RELATIONSHIPS OF THE SOUTH AFRICAN FOSSTL FROG 57 Sphenethmoid The sphenethmoid is well developed (Fig. 2B); in all examples it is a singleossification that extends posteriorly almost to the posterior borders of the palatalvacuities (SAM-9941, K4600d, K4635). Just anterior to this point, large opticforamina are visible (SAM-9941, K4609b, K4635). Crushing has usuallyobscured the contours of the sphenethmoid, but in SAM-9941 and 9940 particu-larly it is clear that its apparent wideness (observable on many specimens
Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum . PMX. RELATIONSHIPS OF THE SOUTH AFRICAN FOSSTL FROG 57 Sphenethmoid The sphenethmoid is well developed (Fig. 2B); in all examples it is a singleossification that extends posteriorly almost to the posterior borders of the palatalvacuities (SAM-9941, K4600d, K4635). Just anterior to this point, large opticforamina are visible (SAM-9941, K4609b, K4635). Crushing has usuallyobscured the contours of the sphenethmoid, but in SAM-9941 and 9940 particu-larly it is clear that its apparent wideness (observable on many specimens) is notthe result of crushing. In these two specimens the lateral sides are seen to con-verge ventrally from their contact with the frontoparietals, and form a broadwedge-shaped bone whose laterally-keeled, flattened ventral surface is capped bythe long, narrow parasphenoid. Anteriorly, as the sphenethmoid expands laterallyinto the planum antorbitale, there is a constricted region (SAM-9941, K4597c,K4609b). Anterolaterally, the arms of the planum antorbitale extend to themaxi
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Keywords: ., bookcentury1800, bookdecade1890, booki, booksubjectnaturalhistory
