THE SKULL OF REPTILES 2 J 



may not extend in front of the basisphenoid. It has been homolo- 

 gized by Broom with the median vomer of mammals, whence the 

 name prevomers for the paired bones in front, the so-called vomers. 

 Ethmoid {eth) or Sphencthmoid. In the temnospondyl amphibians 

 (Fig. II e-g), between the orbits and in front of the optic foramina, 

 there is a pair of thin bones lying closely below the frontals and 

 united with the parasphenoid below, enclosing an undivided cavity 

 for the olfactory lobes, opening into the nasal and paranasal cavities 

 in front of the orbits. Similar bones have been observed in various 

 cotylosaurs (Fig. 13) and theromorphs, and are probably constant 

 among early reptiles. They have been called sphenethmoids, though 

 they have no immediate relation to the sphenoid. Probably the 

 median ethmoidal plate arose from the fusion of these bones. There 

 was no median ossified interorbital septum in these reptiles, and not 

 probably any median septum. A cartilaginous interorbital septum 

 is present in most modern reptiles but is ossified in none. 



Skull Elements — Synonyms 



Ectopterygoid = Transpalatine, Transverse. 



Interparietal = Dermosupraoccipital, Dermooccipital, Postparietal. 



Postoptic = Laterosphenoid, Otosphenoid, "Alisphenoid." 



Paroccipital = Opisthotic. 



Prootic = Petrosal. 



Prearticular = Goniale. 



Postsplenial = Preangular. 



Splenial = Opercular. 



Supratemporal = Supramastoid, Suprasquamosal. 



Squamosal = Prosquamosal. 



Tabular = "Epiotic," Postparietal [sic] ^ 



The Mandible 



The mandible of reptiles was composed primitively of eight, 

 possibly nine, separate bones, differing from that of their temnospon- 

 dyl antecedents (Figs. 14, 15) only in the loss of one or two slender 

 bones along the inner margin of the teeth, the precoronoid and inter- 

 coronoid. All of these, except the postsplenial, known in a single 

 cotylosaur (Fig. 18), have persisted to modern times, though never 

 all in the same reptile, none having more than six, and some but five. 



The relations of these bones will be seen in the accompanying 



^ [Possibly "paroccipital plate" was intended. — Ed.] 



