2 5 6 



DIPNOI 



structure of the skull, with large median elements, they approach 

 Dipterus. 



Uronemus, Ag. ; Carboniferous, Scotland. Probably also Conchopoma, 

 Kner ; Permian, Germany. 



Family DIPTERIDAE. A heterocercal tail, and two dorsal and one 

 anal fin (Fig. 226). The superficial cranial bones and the scales are 

 thick, and covered with an outer layer of cosmine (Figs. 202, 210, 225). 

 The head-plates are numerous, the median series large, and the parietals 

 and frontal s small. The ossification of the endoskeleton seems to be more 

 complete than in modern Dipnoi ; the auditory capsule, the quadrate, and 



af. 



FIG. 227. 



Restorations from Traquair of A, Uronemus lobatus, Ag., Lower Carboniferous; B, 

 pleuroji Andcrsoni, Huxley, Upper Devonian ; C, Scauinenacia curta, Whiteaves, Upper Devonian. 

 a.d.f, anterior dorsal tin ; a./, anal tin ; d.f, dorsal fin ; ef, epichordal lobe, and h.f, hypochordal 

 lobe, of caudal fin ; p.d.f, posterior dorsal fin ; p.f, pelvic fin ; pt.f, pectoral fin ; v.f, ventral fin. 



the articular are bony. Paired ventral gular plates are present. The 

 teeth have tuberculated ridges [299, 312, 447, 505]. 



According to Dollo, Dipterus represent the most primitive Dipnoan 

 type (see p. 233). The presence of typical cosmine is a striking 

 point of resemblance with the Osteolepidoti. The more pronounced 

 ossification may perhaps also be primitive. But the arrangement of the 

 cranial covering bones points rather to the Dipterids being a highly 

 specialised offshoot from the base of the Dipnoan stem. 



Dipterus, Sedg. and Murch. Conchodus, M'Coy ; Devonian, Europe. 

 Palaedaphus, v. Ben. and de Kon. Ganorhynchus, Traq. ; Devonian f 

 Europe, and N. America. 



