160 INTRODUCTION TO EVOLUTION 



of the mouth. Thus terrestrial descendants of the Crossopterygii could 

 breathe through the nose, with the mouth closed. 



The nearest living relative of these ancestral crossopterygians is the 

 coelacanth fish, Latimeria, discovered in 1938. Previously the coelacanths 

 were known only from fossils; they were thought to have become extinct 



FIG. 8.16. A Devonian shark, Cladoselache; length about 3 feet. 



at the close of the Cretaceous period. Then in the winter of 1938-1939 a 

 specimen was caught off the coast of South Africa. Intensive search for 

 other specimens was fruitless at first, but since 1952 several specimens 

 have been obtained near the Comoro Islands off Madagascar. The drama 

 of discovery connected with the first and second specimens makes a fasci- 

 nating story as told by the scientist most concerned, Dr. J. L. B. Smith 



FIG. 8.17. Crossopterygian fish, Eus/fienopferon; length about 2 feet. (Reprinted by 

 permission of the publishers from Percy Edward Raymond, Prehistoric Life, Cambridge, 

 Mass.: Harvard University Press, 1939, p. 98.) 



(1956). The modern coelacanth differs from ancestral lobe-finned fishes by 

 having only a vestige of an air bladder (Millot, 1954), and no internal 

 nostrils. Yet the creature is of great interest because of the strong possi- 

 bility that it has retained many primitive characteristics of tissues and in- 

 ternal organs, and hence may give us clues as to the nature of these features 

 in the ancestral Crossopterygii. The lobe fins are of especial interest; they 

 have complex musculature, and observation of living specimens indicates 

 that the fins are capable of a great variety of movements (Millot, 1955). 



