THE SPECIES PROBLEM WITH 

 FOSSIL ANIMALS 



JOHN IMBRIE: COLUMBIA UNIVERSITY, NEW YORK, n.y. 



In spite of the extended attention this problem has received, 

 the nature of fossil species remains one of the most controversial 

 topics in paleontology. That this should be so in a decade that 

 has witnessed the publication of numerous synoptic studies on 

 the origin of species may surprise some students unfamiliar with 

 the materials and problems of paleontology. But two key ques- 

 tions are still being asked: What is a fossil species? How can 

 fossil species be recognized? 



In defining fossil species it would be possible to ignore living 

 organisms completely and to frame definitions strictly in terms 

 of fossils. In fact, such an unbiological approach to paleontolog- 

 ical taxonomy is almost, but not quite, forced upon us in dealing 

 with some groups such as the conodonts whose biological func- 

 tions are obscure. But most attempts at a definition of fossil spe- 

 cies begin with a review of species concepts held by students 

 of living, sexual organisms, and from this foundation construct 

 a theoretical model of fossil species. The concept of fossil species 

 held by most paleontologists is largely an inference, an inference 

 based both on the observed structure of living species and on 

 a theoretical model of the evolutionary mechanism. 



Paleontologists by no means agree on what a fossil species is. 

 Burma (1954), for example, has given thoughtful expression to 

 the thesis that species do not have an objective reality, a view 

 that is rejected by Simpson (1951) and others. In a symposium 

 on paleontological species, Eagar (1956) holds that for certain 

 groups of fossil clams a workable species concept must be 

 typological. Other students, including Newell (1956) and Syl- 

 vester-Bradley (1956), maintain that the concept of interbreed- 



125 



