256 



ANOMODONTS. 



Anomodonts are met with in the Triassic rocks, and are represented by at 

 least four well-marked subordinal types. In the first group, known as Mammal - 



SKULL AND TEETH OP GALESAUB 



UPPER SURFACE OF THE SKULL OF A PAVEMENT- 

 TOOTHED anomodont (J nat. size). 



toothed (Theriodont) Reptiles, the teeth, 

 as exemplified in the figure of the skull 

 of the African galesaur, are differentiated 

 into incisors, tusks, and cheek-teeth ; the 

 latter frequently having three cusps 

 ranged in a longitudinal series. Whether, 

 however, this marked mammalian type 

 of dentition is indicative of genetic affinity 

 with Mammals, may be open to doubt, as it is quite as likely to be due to parallelism 

 in development. Another modification is presented by the Dicynodonts of England, 

 Africa, and India, in which the jaws formed a horny beak, either destitute of 

 teeth, as in the tortoises, or provided with a huge pair of tusks in the upper 



jaw; some of these reptiles being of 

 gigantic size. A third group, known as 

 Pavement-toothed, or Placodont Reptiles, 

 which should probably be included in the 

 order, are characterised by the presence 

 of broad, flattened teeth on the palate and 

 jaws, as shown in the figure on p. 5 ; the 

 skull being very short and more or less 

 triangular, with the double nostrils situated 

 near the extremity of the muzzle, some 

 distance in advance of the sockets of the 

 eyes, which occupy a nearly central posi- 

 tion. In all these forms, the skull has 

 large temporal fossae in the hinder part of 

 the upper surface ; but in the Wall-toothed or Pariasaurian Anomodonts, as shown 

 in the cut, the hinder part of the skull was roofed over by bone, in the manner 

 characterising the Labyrinthodont Amphibians, to which these reptiles were allied ; 

 a peculiar sculpturing of the surface of the skull being another point of resem- 

 blance. In the species, of which the skull is figured, a number of spines surmounted 

 the head ; but these were wanting in the African pariasaur, which was a gigantic 

 creature, with a somewhat frog-like head, an apology for a tail, and powerful 

 short limbs, in which the toes were armed with long claws. 



UPPER SURFACE OF THE SKULL OF A WALL-TOOTHED 



anomodont (\ nat. size). 



