No. 446.] RECLASSIFICATION OF THE REPTILIA. 1 03 



which are single in Therocephalia. These cynodonts have lost 

 several of the other more primitive characters of the theroceph- 

 alians, such as teeth in the pal- 

 ate; and their specialization is in 

 the direction of the mammalia. 

 The phalangeal formula is 2. 3. 

 3. 3. 3. They include three 

 families, typified respectively by 

 the genera Lycosaurus, Cynog- 

 nathus, and Gomphognathus. 



2. Order Dicynodontia Owen. 



This term was originally used 

 as a family " term, under Ano- 

 modontia, by Owen in 1859; 

 Huxley raised it to the rank of 

 an order from the types Dicyno- 

 don, Oudenodon. The latter, 

 Owen (1859) had placed in the 

 "family" Cryptodontia, in ref- 

 erence to the absence of teeth. 

 Despite the high specialization 

 of the dentition, these animals 

 retain the more primitive fea- 

 tures of the single condyle, of the cleithrum or epiclavicle, of 

 the large quadrates. On the other hand, like the cynodonts, 

 they show a rudimentary secondary palate. They approach the 

 mammals also in the loss of the prevomers and development of 

 the vomer (parasphenoid). 



In the most primitive family of Endothiodontidae one or more 

 series of molar teeth are present on the maxillaries and dentaries ; 

 the interclavicle is a rounded plate as in the Stegocephalia^ In 

 the more specialized Dicynodontida., maxillary teeth are absent, 

 or present as a pair of tusks, and there are no teeth in the lower 

 jaw; the interclavicle is elongated, and a cleithrum is present. 

 The third family, Lystrosaurid^, exhibits a small interclavicle, 

 and no cleithrum. A fourth family, Cistecephalid^ is doubtfully 

 ranked here by Broom. 



