Table i». — Frequency distribution of total gill rak-er.i in Albul 

 iiemoptera and A. vulpes 



Tabi.k 10. Fr«iucnr!i (hslrihidion of branchioaleijal rui/x in 

 Albula Iiemoptera and A. vulpes 



Species 



,1. nemoplera (.Atlantic). 

 --1. fumoplera (Pacific).-. 

 A.ridpes (Atlantic) 



Mean 

 13.1) 

 14. U 

 11.0 



Tmile 11. Frt'iiiicncn dislrihiitiori of vertebrae in .Mlmla 

 Iiemoptera ami A. vulpes 



Species 



Vertebrae 



-1. nemoplera (Atlantic) 

 .1. nemoplera (Pacific).. 

 A. futpes (Atlantic) 



2o;.. 



20 .. 

 20 10 



Mean 

 78.4 

 78.5 

 (19. 5 



a comparison of their detailed structures. From 

 the characters studied there is more indica- 

 tion of similarity than divergence. The most 

 important differences between the two species 

 are the larger mouth and the longer last dorsal 

 and anal rays in A. ncmoptera. Other differ- 

 ences were in dentition, certain proportions, 

 meristic characters, and color markings. 



Even their ancestry, as reconstructed from 

 fossil material, indicates that A. vulpes and 

 A. nemo])fcra should not be considered as rep- 

 resenting sepai-ate monotypic genera. Frizzell 

 (1965), after studying otoliths, suggested a 

 phylogeny of albulid genera dating back to the 

 Cretaceous. Although he retained Albula and 

 Dixonina as separate genera, his illustrations, 

 descriptions, and comments indicate that these 

 two genera are more closely related to each 

 other than either is to any of their predeces- 

 sors. Both Albula and Dixonina are tentatively 

 shown by Frizzell to be descended from the 

 Eocene-Oligocene genus Metalbula Frizzell. 



Radiographs of 20 juvenile to adult A. vulp(s 

 and 40 juvenile to adult A. nemoptrra indicate 



that the otolith (sagitta) of A. vulpes is more 

 inclined, with respect to the axis of the verte- 

 bral column, than that of A. nemopteia. This 

 has been confirmed by Don L. Frizzell (per- 

 sonal correspondence). 



ALBULA NEMOPLERA (FOWLER) 



Dixonina nemoplera Fowler, 1911; 652 (orig- 

 inal description) ; Santo Domingo, West In- 

 dies. Myers, 1936: 83-85 (new record; com- 

 pared with Albula; Acapulco, Mexico). 

 Walford, 1939: 119 (identification of draw- 

 ing from Kumada and Hiyama, 1937; 

 Gulf of California). Beebe, 1942: 45 (com- 

 pared with D. pacifica). Rivas, 1952: 3 

 (popular account of new record; Port An- 

 tonia, Jamaica). Hildebrand, 1963: 143-145 

 (description; relationship; range; synonymy; 

 Acapulco, Mexico). Caldwell and Caldwell, 

 1964: 4 (dorsal fin rays; Jamaica). Berry, 

 1964: 722 (synonymy with D. pacifica ques- 

 tioned) . Frizzell, 1965: 85 (otolith-based tax- 

 onomy, classification, lineage, paleoecology). 

 Albula nemoptera Metzelaar, 1919: 9 (descrip- 

 tion; comments; generic separation not justi- 

 fied; Puerto Cabello, Venezuela). 

 Albula vulpes (not of Linnaeus) Kumada and 

 Hiyama, 1937: (colored plate; Gulf of Cali- 

 fornia). Caldwell and Caldwell, 1964: 4-5 

 (dorsal fin rays; tentative identification; 

 Caledonia Bay, Panama). 

 Dixonina pacifica Beebe, 1942: 43 (original de- 

 scription; compared with D. nemoptera; 

 Potrero Grande, Culebra Bay, and Piedra 

 Blanca, Costa Rica). Hildebrand, 1963: 

 144-145 (synonymized with D. nemoptera; 

 Acapulco, Mexico). Berry, 1964: 722 (syno- 

 nymy with D. nemoptera questioned). 

 A comparison of specimens from the At- 

 lantic and the Pacific Oceans (tables 2 to 11) 

 indicates that jjacifica should not be considered 

 as specifically distinct from nemopteia. No 

 significant differences were found in 18 of the 

 23 proportional characters studied (table 2). 

 In the five characters that show differences 

 (dorsal and anal fin height, last dorsal ray 

 length, upper and lower caudal lobe length) the 

 overlap is quite broad. Tables 3 to 11 show 

 that meristic characters are about the same in 

 the Atlantic and Pacific populations with the 



254 



U.S. FISH AND WILDLIKE SERVICE 



