Licence: Public Domain Mark
Credit: On the Gomphodontia / 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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![PHILOSOPHICAL TRANSACTIONS. 1. Researches oil the Structure, Organization, and Classification of Reptilia.—.Part IX., Section 4. On the Gomphodontia. By H. G. Seeley, F.R.S. Received and Read June 21, 1894.—Revised November, 1894. [Plates 1, 2.] Introduction. The Gomphodontia comprises animals with a Theriodont type of dentition, in which the molar teeth are expanded transversely, and have more or less tuberculate crowns, of the type shown in Diademodon. The superior and inferior teeth are opposed to each other, and the crowns become worn with use, as in Ungulate and other Mammals, and as in Iguanodont Reptiles. The canine teeth of the upper jaw appear to be worn at their extremities. The skull is known from the genera Gomphognathus, Trirachodon, and Micro- gomphodon. It appears to show mammalian proportions and aspect, in the definition of the large temporal vacuities by a zygomatic arch, which is formed by the malar and squamosal bones, and in the separation of those vacuities from each other by a long narrow parietal crest. The orbit of the eye, however, is separated from the zygomatic vacuity by a post-frontal bone, so that the structure is distinct from that which obtains in Ungulates, Lemurs, and all Mammals in which the orbit is similarly complete. There are two well-defined occipital condyles at the back of the base of the skull, united to each other inferiorly in a way that is closely paralleled in some Mammals. Each condyle is transversely wide, and convex, and together they form a curve, which differs from most Mammals in the smallness of the median vertical notch between them, which is scarcely so much developed as in certain Cetacea. The occipital plate of the skull has a triangular form, and is more or less concave, as in many Mammals, without any conspicuous perforation, except the foramen magnum.- It appears to be formed substantially on the plan of the occipital plate in Dicynodon. The absence of a large lateral foramen distinguishes it from the occipital MDCCCXOV.—B. B 28.3.95](https://iiif.wellcomecollection.org/image/b2241731x_0003.jp2/full/800%2C/0/default.jpg)
