1910.] The Mammal-Ukc Reptiles. 117 



Anomodontia Proper. 



The Anomodontia, as limited by Broom (1905. 1) are also Permian forms. 

 They are contemporaneous with the known Therocephalia but are believed 

 by Broom to have been derived from earlier members of that order. The 

 typical genus Dicynodon and its allies are very aberrant in skull structure. 

 The edentulous muzzle was encased in a horny beak and there are either two 

 great walrus-like tusks or none at all. The related Endothiodonts (Seeley, 

 1895.1, p. 1015; Broom, 1905.1) retain small round teeth on the maxillaries, 

 palatines and pterygoids, thus recalling the Cotylosaurs. All are distin- 

 guished by the peculiar -/ -shaped squamoso-quadrate region. The well- 

 developed secondary palate is about the only striking analogy to mammalian 

 conditions among the cranial characters. The manus and pes, which are 

 known especially in Oudenodon (Broom, 1901), are probably a development 

 of the Cotylosaurian type. They show strong resemblances in the phalangeal 

 formula and in the ungual phalanges to the Monotreme type (c/. Fig. 28, 

 p. 440). The carpals and tarsals, while very generalized, also show strong 

 evidence of affinity with the stem of the mammals (see p. 439). The 

 Endothiodonts retain small teeth in the roof of the mouth but are otherwise 

 like the typical Anomodonts (Broom, 1905.1). 



Cynodontia {Theriodontia in part). 



These are the forms that Owen, Seeley, Osborn and Broom have recog- 

 nized as standing close to the stem of the mammals. They are found in the 

 Upper Triassic of South Africa and are separated by a wide stratigraphic 

 interval from the Permian Therocephalians (Broom, 1907.4). They have 

 advanced much beyond the Therocephalians: notably, in regard to the 

 dentition, in the loss of the pineal foramen, and in all those characters which 

 tend to ally them with the mammals, — especially in the reduction of the 

 quadrate, articular, angulare and in the enlargement of the dentary (c/. Figs. 

 \B, 2B). 



II. Relations of the Mammalia to the Triassic Cynodontia. 



The structural relations of the Cynodonts to the Mammalia may be 

 considered under two general headings: first, their primitive reptilian char- 

 acters, secondly, the characters in which they foreshadow the mammals. 

 This leads to a discussion of the fate of the quadrate and the origin of the 

 mammalian auditorv ossicles. 



