Proceedings of 

 the United States 

 National Museu 



m 



SMITHSONIAN INSTITUTION . WASHINGTON, D.C. 



A REVISION OF THE HAMMERHEAD SHARKS 

 (FAMILY SPHYRNIDAE) 



By Carter R. Gilbert 



Introduction 



The hammerhead sharks, so named because of the unusual lateral 

 expansion of the head, comprise a moderately large family of sharks 

 occurring in tropical and temperate waters throughout the world. 

 They are a rather old group; fossil remains have been found in Eocene 

 deposits from Vu-ginia (Shelton P. Applegate, pers. comm.). The 

 family belongs to the relatively speciose and poorly known suborder 

 Galeoidea, in which are found most of the large and all of the dangerous 

 kinds of sharks. Since the hammerheads are well defined, and, with 

 one exception, adequate study material exists for all the species, they 

 form an ideal taxon for systematic study. 



The most recent works of a revisionary nature that have appeared 

 on the hammerheads (Tortonese, 1950, pp. 1-39; Fraser-Brunner, 

 1950, pp. 213-219) list eleven and ten species, respectively; however, 

 the above authors were unable to examme examples of all the species 

 treated or all the extant types. Consequently, a number of con- 

 clusions were reached that now appear to be erroneous. The following 



' Florida State Museum, University of Florida, Gainesville. 



