New Fossil Fishes from Wyoming 



Museum paleontologists have discovered the oldest ancestral 

 relatives of a modern "living fossil"— the lungfish 



ROBERT H. DENISON 

 Curator, Fossil Fishes 



Nearly 400 million years ago the De- 

 vonian sea overflowed the margins of the 

 western geosyncline and spread over the 

 flatlands of what is today Wyoming, 

 Utah, and Idaho. Near the margins of 

 this advancing sea and in streams emp- 

 tying into it lived a variety of fishes that 

 would appear strange to our modern eyes. 

 The commonest of these were armored 

 fishes, including weird jawless ostraco- 

 derms, and jawed fishes, called arthro- 

 dires, that are distantly related to sharks. 

 This fish fauna, one of the earliest that 

 is known at all adequately, has been the 

 object of Museum expeditions in 1950, 



Page 6 



1953, and 1959 to western states. It has 

 been found in sediments deposited in 

 estuaries and bays of the advancing sea 

 in a few localities in Wyoming, north- 

 ern Utah, and southeastern Idaho. 



In 1953 a geology student of the Uni- 

 versity of Wyoming discovered a new 

 locality in the Bighorn Mountains of Wy- 

 oming, and while returning from our 

 1959 collecting trip we stopped off briefly 

 to see it. It appeared to be very promis- 

 ing; in fact, it was the only locality that 

 I had seen where the rock was easily 

 workable, and the fossils were sufficiently 

 abundant so that one could sit down and 



quarry them out. Not only that, but 

 certain levels contained well preserved 

 plants and eurypterids, or "sea scor- 

 pions." So I planned a return visit for 

 1960, with our invertebrate paleontolo- 

 gist, Dr. Eugene S. Richardson, to watch 

 for eurypterids, and some younger assist- 

 ants, Dave Denison, Pete Richardson, 

 and a graduate student from the Uni- 

 versity of Wyoming, John Cutler, to do 

 most of the heavy digging. 



Our quarry was opened high on the 

 side of a canyon, in limestones that were 

 deposited in an ancient channel, possi- 

 bly representing an estuary of the De- 



