On Oudenodon (Aulacocephalus) pithecops from Cape Colony / by H.G. Seeley.

  • Seeley, H. G. (Harry Govier), 1839-1909.
Date:
1898
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Licence: Public Domain Mark

Credit: On Oudenodon (Aulacocephalus) pithecops from Cape Colony / 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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    f Extracted from the Geological Magazine, Decade IV, Vol. V, No. 405, p. 107, March, 1898.] On Oudexodox (Aulacochphalus) pithecops from the Dicynodon Beds of East London, Cape Colony. By H. G. Seeley, F.R.S., Professor of Geology, King’s College, London. fTHB genus Ondenodon of A. G. Bain, 1856, was adopted by Sir 1 Richard Owen, and defined as comprising Anomodont reptiles of the type of Dicynodon, hut absolutely toothless. Still, they were referred to a family Cryptodontia, under the belief that the j teeth were immature, and had their development arrested, so that they never descended to the adveolar margin. A transition might l easily be made from the caniniform production upward of the alveolar border seen in Oudenodon to the small teeth in Dicynodon duhius and D. recurvidens, which are in contrast to the great lateral ridges formed by the roots of the teeth in most species of the genus. The species striyiceps was referred first to Dicynodon and then to Oudenodon. Owen described eight species, which differ from each other in the elongation of the head, in the form of the preorbital region !and its prolongation in front of the nares, in the forms of the orbits of the eyes, aud the anterior nares, and in the median postorbital region ; being either a sharp ridge or a more or less flattened concave >. channel. These characters might have been used to define genera. The species fall, more or less easily, into two groups, and this is also true for Dicynodon. The same characters differentiate the short-nosed from the long-nosed species of both types, suggesting - that the genera based on presence or absence of teeth in this case are artificial. Thus, the short-nosed Oudenodons are almost in- distinguishable except as species from the short-nosed Dicynodons; and the long-nosed Oudenodons similarly approximate in skull-shape to the long-nosed forms of Dicynodon. I therefore propose to divide Oudenodon into two subgenera. The short-nosed types, with a wide flattened concave region between the temporal vacuities, the parietal foramen in its middle length, and orbits more or less circular and directed forward and upward, are represented by the species 0. JDaiui, 0 raniceps, and 0. megalops. They may be indicated by the name Aulacocephalos. The prognathous species have the orbits more lateral, the parietal foramen just behind the orbits, and a sharp median ridge between the temporal vacuities which may extend along their length or be limited to a part of it. This group is represented by the species 0. magnus, 0. prognalhus, 0. brevirostris, and 0. Greyi, and may be indicated by the name Ehachiooephalus. In the same way 1 would divide Dicynodon into two subgenera. The short-nosed species have a broad concave parietal interspace between the outwardly inclined faces of the postfrontal bones, which make the inner borders of the temporal vacuities. The parietal foramen is in the middle of this area. The nares are scarcely seen when the skull is viewed from above, and owing to the shortening of the snout the orbits are directed forward. The species include D. Baini, D. tigriceps, and presumably D. lestudiceps, aud may be defined by the name Aulaoephalodon.