Additional evidence as to the dentition and structure of the skull in the South African fossil reptile genus Diademodon / by H.G. Seeley.

  • Harry Govier Seeley
Date:
1908
Catalogue details

Licence: In copyright

Credit: Additional evidence as to the dentition and structure of the skull in the South African fossil reptile genus Diademodon / by H.G. Seeley. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    61:3 orbit where the margin is compressed posteriorly and rounded in front. The bone is in front of tbe post-frontal, external to the frontal, makes an oblique suture with the nasal, and a narrow junction with the lachrymal bone, as its sutural junctions diverge outward and forward. It is | inch long from the post-frontal to the lachrymal and inch wide at the fronto-nasal suture, where it is widest in about its middle length. The inner short border next the frontal is parallel to the longer external border above the orbit and lachrymal. The pre-frontal bone forms a large part of the internal anterior wall of the orbit. The nasal bones, somewhat lanceolate in form, are imperfect anteriorly. They extend from the frontal bones forward as preserved to between the pair of pits on the front of the snout, which are not seen in Dicidemodon browni, with a length of 1-j4^ inch, and in this length they are not in contact with the pre- maxillary bones. They are separated from each other by a fine straight suture, and widen from tbe frontal suture anteriorly, with the lateral divergence of the sutures dividing them from the pre- frontal and lachrymal bones, to 1] inch at the front of tbe lachrymal bones ; and anteriorly the sutures between them and the maxillary bones converge forward, to a transverse width over the nasal bones of half an inch, at the anterior fracture through the lateral-nasal pits. The bones are smooth, convex from side to side, and slightly raised posteriorly, with a partial prolongation forward of the median frontal sutural ridge. The lachrymal bone is best exposed on the left side, where I have partially removed the matrix from the orbit. It is at the front of the orbit between the maxillary bone below and the nasal and pre-frontal bones above. Externally it is of irregular sub- quadrate form, half an inch in each measurement. It has a considerable extension in the front of the orbit internally, below the pre-frontal bone. On the lower part of the inner front border the bone is pierced by two circular canals placed one below the other. The maxillary bones form the sides of the face from the hinder fracture at the back of the alveolar tract below the orbit, where the bone is inch deep, forward to the anterior fracture, where the depth is 1-A inch. The ascending orbital border below the orbit is compressed, rounded, and slightly reflected outward. Below the lachrymal canal the depth to the alveolar border is inch. A slight wide shallow concavity extends longitudinally forward, from the orbital junction between the lachrymal and maxillary bones; but on the right side the bone appears to be accidentally impressed in this region. The lowTer part of the maxillary bone is moderately concave in length, and markedly convex downward owing to the compression of the bone imme- diately above tbe molar teeth. On the convex ridge above ape two ovate foramina above the teeth, such as occur in many fossil reptiles. The palate has shared in the side to side compression and Laj