A LIVING FOSSIL — SMITH 325 



bers over a wide area, they diminished, until finally all traces ceased 

 before the end of the Mesozoic era — 50 million years ago. Those 

 important fishes had all vanished. Important because they were a 

 link between the early intriguing creatures about whose structure we 

 know so little, and the later vertebrates which have given rise finally 

 to man. 



The Crossopterygian stock developed principally through a group 

 known as the Rhipidistians. These flourished from 300 million 

 years ago for about 100 million years. Some of those fishes were 

 the ancestral forms which gave rise, almost simultaneously, to three 

 branches of the evolutionary tree: (a) The lungfishes, a thin feeble 

 line that has survived by living an almost isolated life under condi- 

 tions that scarcely any other creatures can stand; (h) Actinistian 

 fishes, the Coelacanthidae, a vigorous branch that flourished for a 

 long period and then just petered out long ago (or was thought to 

 have done so) ; and (<?) the amphibia, the origin of all land verte- 

 brates. The two latter groups must have budded off from the parent 

 stock very close together. It is not even unlikely that some of the early 

 Coelacanthids made expeditions ashore along with those unknown 

 amphibian ancestors. If that is so, then for some reason they re- 

 turned to the water, and extinction, while the amphibian stock 

 multiplied and throve. 



Because of their close connection with the origin of land ver- 

 tebrates, Crossopterygian fishes have been the subject of most in- 

 tensive researches. In only a few cases have scientists been able to 

 find anything like complete remains. Mostly there are fragments. In 

 almost all cases the bones of the front part of the snout are missing. 

 There have been found very few clues as to structure other than of the 

 hard parts. All very tantalizing, especially as that "missing link" be- 

 tween fishes and amphibians is still missing. 



Now, suddenly, there has appeared this great 5-foot fish, bearing the 

 full panoply of his early Mesozoic forbears, but larger than any of 

 them. He is neither puny nor degenerate like the lungfishes, but 

 a great robust animal prepared and fitted to face all the risks in the 

 sea (except a trawl net!). It is as if a fish of 150 million years 

 ago had suddenly come to life. In that incomprehensibly long 

 stretch of time this species has remained virtually unchanged, evi- 

 dently completely satisfied with itself. In every way this is a true 

 Coelacanthid from that remote past. For at least 150 million years 

 this representative of that ancient but vigorous line has lived in such 

 obscurity as never to have left any known traces of its existence. 



The discovery of this Coelacanth is a confirmatory link in the 

 chain of evidence upon which the theory of evolution is based. It 

 stands as a high tribute to the reconstructional ability of scientists 



