x. 4 COELACANTIIS 271 



end of the palate, bordered by the premaxillae, maxillae, palatines, and 

 prevomers. These fishes may have breathed air; they certainly also 

 possessed gills, covered with an operculum. 



Animals of this sort seem to have been abundant in Devonian 

 waters and by the end of that period had diverged into several different 

 lines. It is interesting that the tendencies shown by these lines arc- 

 similar to those that we discovered in the evolution of the Actino- 

 pterygii. Some of the later osteolepids became shorter in body, the 

 tails tended to become symmetrical (diphycercal) and the scales to 



Fig. 162. Coelacanth, Latimeria chalumnae, female. Length 142 cm. Caught 1954 

 near Anjouan. (After Grasse.) 



become thinner and overlapping. *Dip!opterax and *Eiistheiiopteron 

 represent separate lines from the late Devonian, both showing these 

 characters. Probably the development of these features depends on 

 the use of the air-bladder as a hydrostatic organ and the associated 

 changes in the method of swimming. 



4. Coelacanths 



The osteolepids became rare in the Carboniferous and disappeared 

 after the early Permian, but a line descended directly from them 

 remained common through the Mesozoic and still survives today. 

 These coelacanths (Fig. 162) show certain very characteristic features, 

 which enabled the strange fish brought to the museum at East 

 London, South Africa, to be recognized immediately as belonging to 

 the group. They are rather deep-bodied animals, with a characteristic 

 three-lobed diphycercal tail. The type first appeared in the late 

 Devonian and was obviously derived from osteolepid ancestry having 

 two dorsal fins, diphycercal tail, lobed fins, and a rhipidistian pattern 

 of skull bones, including in most forms a fronto-parietal joint. There 

 was a calcified air-bladder. *CoelacantJius and other Carboniferous 



