The caudal fin of T. alalunga has a narrow, white 

 traihng margin that distinguishes it from all other 

 Thunnns, in wiiich the white margin is lacking. 



Specific Characters. The uniformly white- 

 margined dusky finlets of T. atlanticus, the white 

 caudal margin of T. alalunga, the horizontally elon- 



gated ventrolateral spots of T. tonggol, and the yel- 

 low caudal keels of T. maccoyii are the only color 

 characters we regard as generally useful in distin- 

 guishing species, and confusing examples of other 

 species with these same characters have been ob- 

 served. 



PART 2. SYSTEMATICS 



Workers have differed in their interpretations of 

 the suprageneric relationship of tunas and the 

 mackerel-like fishes. Regan (1909) and Starks (1910) 

 placed all of these fishes in the single family Scom- 

 bridae. Kishinouye (1915, 1917, 1923) recognized 

 four families: Scombridae, Cybiidae, Katsuwonidae, 

 and Thunnidae, the last two of which he (1917, 1923) 

 recognized as an order Plecostei, separate from the 

 Teleostei, in which he included all other higher bony 

 fishes. Takahashi (1924, 1926) disagreed with the 

 recognition of a distinct order but did not alter the 

 four families. More recently, Fraser-Brimner (1950) 

 placed the tuna-like and mackerel-like fishes back in 

 the Scombridae. Berg (1940, 1955) is one of the 

 few recent taxonomists who followed Kishinouye in 

 placing the tunas in a separate order Thunniformes. 

 For reasons outlined elsewhere (Collette and Gibbs, 

 1963), we follow Regan, Starks, and Fraser-Brunner 

 in placing all of the tunas and other mackerel-like 

 fishes in the family Scombridae. 



It is possible to divide the Scombridae into smaller 

 units. Gasterochisma is so different from the other 

 scombrids that it deserves at least subfamily status. 

 Fraser-Brunner (1950) recognized only the subfamilies 

 Gasterochismatinae and Scombrinae. Nakamura 

 (1965) considered Thunnus and Eulhijnnus (includ- 

 ing Katsuwomis) as a third subfamily, Thunninae. 

 In the comparative diagnosis of the genus Thunnus 

 which follows, we give suggestions of other possible 

 subdivisions. Until a thorough anatomical study is 

 completed, however, we do not wish to present 

 formally a revised family classification. 



THUNNUS SOUTH, 1845 



Thynnus Cuvier, 1817: 313 (type-species: Scomber 

 thynnus Linnaeus, 1758, by absolute tautonymy; 

 preoccupied by Thynnus Fabricius, 1775, a genus 

 of Hymenoptera). 



Orcynus Cuvier, 1817: 314 (type-species: Scomber 

 germo Lacepede, 1800 [= Scomber alalunga Bon- 

 naterre, 1788], by subsequent designation of Jordan, 



1888: 180; preoccupied by Orcynus Rafinesque, 

 1815, a substitute for Scomberoides Lacepede). 



Thinnus S. D. W., 1837 (emendation of Thynnus 

 Cuvier, 1817, therefore taking the same type- 

 species: Scomber thynnus Linnaeus, 1758; suppres- 

 sion in favor of Thinnus South, 1845 requested by 

 Collette and Gibbs, 1964). 



Thunnus South, 1845 (emendation of r^nnws Cuvier, 

 1817, therefore taking the same type-species: 

 Scomber thynmis Linnaeus, 1758). 



Orycnus Cooper, 1863: 77 (substitute name for 

 Thynnus Cuvier, 1817, and therefore taking the 

 same type-species: Scomber thynnus Linnaeus, 

 1758; not Orycnus of Gill, 1861, a misprint for 

 Orcynus Cuvier, 1817). 



Albacora Jordan, 1888: 180 (substitute name for 

 Thynnus Cuvier, 1817, therefore taking the same 

 type-species: Scomber thynnus Linnaeus, 1758). 



Germo Jordan, 1888: 180 (substitute name for 

 Orcynus Cuvier, 1817, therefore taking the same 

 type-species: Scomber germo Lacepede, 1800 [ = 

 Scomber alalunga Bonnaterre, 1788]). 



Parathunnus Kishinouye, 1923: 442 (type-species: 

 Thunnus mebachi Kishinouye, 1923 [= Thynnus 

 obesus Lowe, 1839], by monotypy). 



Neothunnus Kishinouye, 1923: 445 (type-species: 

 Thynnus macropterus Temminck and Schlegel, 

 1844 [= Scomber albacares Bonnaterre, 1788] by 

 subsequent designation of Jordan and Hubbs, 

 1925:218). 



Kishinoella Jordan and Hubbs, 1925: 219 (type- 

 species: Thunnus rarus Kishinouye, 1923 [= Thyn- 

 nus tonggol Bleeker, 1851] by original designation). 



Semathunnus Yow'hr, 1933: 163 (type-species: Sema- 

 thunnus guildi Fowler, 1933 [= Scomber albacares 

 Bonnaterre, 1788] by original designation). 



Comparative Diagnosis 



The tunas, genus Thunnus, comprise a group 

 of seven closely related species representing the 

 most advanced members of the family Scombridae 



ANATOMY AND SYSTKMATICS OF TUNAS 



97 



