II. Researches on the structure, organization, and classification of the fossil reptilia.—Part IX., section 5. On the skeleton new cynodontia from the karroo rocks

Abstract

This name was originally used, by Sir It. Owen, for the division of the Anomodontia, of which Galesaurus is the type. Subsequently, Theriodontia was defined, so as to be co-extensive with the older Cynodontia, both groups being based upon a type of dentition, which approximates to that of Carnivorous Mammalia. The name Theriodontia, hence, has some appearance of being a synonym of Cynodontia. The group Theriodontia, is obviously a larger group than the original Cynodontia, since its type, Lycosaurus , has simple pointed molar teeth, and it also includes Nythosaurus and Scaloposaurus , in which the molar teeth are laterally cuspidate. The Theriodontia include the Cynodontia, because the Cynodont genera were grouped in this way by Sir It. Owen, and, because there is no evidence of ordinal differences in the skull. The Cynodontia is conveniently distinguished from the Lycosauria by dental, and other minor characters of the skull; and I propose to use the name Cynodontia for animals which resemble Galesaurus in skull structure, and resemble Nythosaurus in the type of molar teeth. The crowns of the cheek teeth not being preserved in Galesaurus , I take Cynogathus , the genus now to be described, as the type of the group, which will be thus defined and limited. This genus makes known, for the first time, the more important parts of the Theriodont skeleton in association with the skull. The small bones of the limbs were not found in Cynognathus . Some account of bones of the extremities in other types of Theriodonts is given in other sections (2, 4, 6) of this paper, but in no case is there similar actual association of those bones and the skull. This sub-order of Therosuchian Anomodontia is defined as having incisor, canine, and laterally cuspidate molar teeth, of carnivorous type. The mandible fits within the upper jaw so as to give the teeth a dividing action, as in shears. The coronoid process of the lower jaw is formed by the dentary bone, and is strongly developed. There is no descending pedicle to the squamosal bone which, with the malar bone, forms a zygoma, placed as in Lemurs and Carnivora; and as in the extinct Mammal Elotherium .