Proceedings of 

 the United States 

 National Museum 



SMITHSONIAN INSTITUTION • WASHINGTON, D.C. 



Volume 118 1967 Number 3537 



REVISION OF SHARKS OF GENUS ISURUS 



WITH DESCRIPTION OF A NEW SPECIES 



(GALEOIDEA, LAMNIDAE) ^ 



By J. A. F. Garrick 



The genus Isurus comprises the mako or mackerel sharks, world- 

 wide in distribution throughout tropical and temperate seas. Opinion 

 from recent accounts as to the number of extant species in the genus 

 ranges from two or three (Bigelow and Schroeder, 1948) to four (Smith, 

 1957, 1958) . In the study reported below, considerably more material 

 has been examined than was available to other workers, and it is 

 concluded that the 12 nominal species of Isurus represent only 1 

 world\\ide species. However, in addition, there is another very dis- 

 tinctive species which does not appear to have been described.^ 

 Presentation of the evidence for these findings and description of the 

 new species are the purposes of this paper. 



This study is based on 35 specimens from which fairly complete 

 measurements of external dimensions have been taken. For another 

 8 specimens only incomplete data are available. In addition some 



1 This study has been supported by grants from the University of New Zealand, 

 by Atomic Energy Commission contract AT(30-1)2409, and by National Science 

 Foundation Grant GB-245. 



2 Department of Zoology, Victoria University of Wellington, New Zealand. 



3 At the time this paper was in galley, Guitart Manday (July 1966) described, 

 under the name Isurus paucus, a mako shark that is clearly the same as the 

 species which I describe as new in this account. For further details, see Addendum. 



219-935—67 663 



