lacrimal canal 

 (dashed tines) 



palatine 

 parasphenoid 



pterygoid 



columella |j 



supratemporal ■^ 



septomaxilla 



inter- 

 temporal 



supratemporal _ 

 tabular C 



Figure 4-23 Fossil amphibians, branchiosaurs, and Eugynnus. A, B, dorsal and ventral views 

 of Amphibamus, o branchiosaur; C, dorsal view of Bronchiosourus, D, E, dorsal and ventral v.ews o 

 Eugynnus; F, lateral view of skull ond mand.ble or Eugynnus; G, medial v,ew of mandible of 

 Eugyrinus. (After Gregory, 1950, and Wotson, 1940) 



pair of palatines. The vomer and palatine each had a large 

 tooth or tusk affixed to them. The posterior part of the 

 palatine was probably separated as the ectopterygoid. The 

 pterygoids were triradiate (three-pronged) and there were 

 large interpterygoid fontanelles. A small epipterygoid ex- 

 tended up from the palatoquadrate, near its attachment to 

 the basipterygoid process, and passed between the Vi and 

 V2 branches of the trigeminal nerve. 



The endocranium had slight exoccipital and basiocci- 

 pital perichondral ossifications. These bones contributed to 

 the single occipital condyle. The exoccipital was perforated 

 by a hypoglossal foramen and formed the posterior margin 

 of the vagus foramen. There was no supraoccipital; the 

 postparietal and tabular had slight flanges extending down 

 over the occipital surface. The otic capsule was ossified, 

 probably from prootic and opisthotic centers. 



The mandible was quite primitive in its cover of dermal 

 bones. It was like that of the branchiosaur but had two 



small splenials along the ventral inner margin. The artic- 

 ular region appears to have been ossified from the supra- 

 angular. There was a foramen for the internal mandibular 

 branch of the facial nerve (chordi tympani) just below the 

 articular area. The branchial skeleton is not known. 



Along with the Seymouriamorpha, Eugynnus is classed as 

 an anthracosaur. The anthracosaurs, or coal lizards, are 

 presumed to be on the direct line of evolution to the reptile. 

 The anthracosaur usually described is Palaeogyrmus (Figure 

 4-24). Only the skull of this Pennsylvanian form is known, 

 but in some detail. The roof was like that of Eugynnus m 

 composition but not in shape. Palaeogvnnus was also consid- 

 erably larger in size; its skull was about six inches long as 

 compared with three-quarters of an inch for that of Eugynnm. 

 The dermal bones showed a canal pattern somewhat more 

 elaborate than that of Eugynnus-, a distinct groove arched 

 over the quadratojugal and up toward the preopercular 

 canal groove. The palate diff'ered in having a small inter- 



86 . HEAD SKELETON OF OTHER TETRAPODS AND CHOANATES 



