256 



DIPNOI 



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

 Diptcrus. 



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

 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, 22 5). 

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

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

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



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

 pleureni Andersoni, Huxley, Upper Devonian ; C, Seav tnenacia eurta, Whiteaves, Upper Devonian. 

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

 lobe, of caudal tin ; p.d.f, posterior dorsal tin ; p.f, pelvic tin ; pt.f, pectoral fin ; r.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. Conchodu.% M'Coy ; Devonian, Europe. 

 Palaeda/phus, v. Ben. and de Kon. Ganorhynchus, Traq. ; Devonian r 

 Europe, and N. America. 



