COHEN and RUSSO VARIATION IN FOURBEARD ROCKLING 



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Fl( ;L'RE 5, — Enchelyopus cimhrius. USNM 217900, standard length 135 mm; photograph of an alizarm preparation m glycerin showing 

 the three different kinds of dorsal fin rays and their skeletal supports. 



number and distribution of supratemporal pores 

 (our Table 9). Unfortunately, he was unable to 

 study all of the species. We have examined six of 

 the nominal Gaidropsarus species that he recog- 

 nized, both species oiCiliata, and, of course, En- 

 vhelyopus (study material of all genera is listed in 

 the Appendix). 



Number of barbels is the only character that 

 unequivocally divides our material according to 

 Svetovidov's classification. 



Proper evaluation of the skull-width character 

 will require the examination of osteological prep- 

 arations, which we have not done. We note, how- 

 ever, that although Ciliata inustela has a notably 

 broad skull, that ofC septentrionalis appears to be 

 narrower. Also, although most species oiGaidrop- 

 Hcinis appear to have narrow skulls, that of G. 

 guttatus appears broad. 



Regarding the size and shape of the vomerine 

 tooth patch, it is highly variable, and although it 

 may serve to distinguish some species it is of 

 doubtful value at the genus level. 



Table 9. — Summary of diagnostic characters for three rockling 

 genera given by Svetovidov (1948). 



Number of supratemporal pores also is a vari- 

 able character. Five of the Gaidropsarus species 

 that we have studied show the pattern given for 

 the genus by Svetovidov (1948), one median and 

 one pair of pores ( = 3). However, G. argentatus has 

 two pairs and no median pores ( = 4). In Ciliata, C. 

 mustela has one pair ( = 2), while C . septentrionalis 

 has three pairs ( = 6). 



As noted above, Wheeler ( 1969) recognized five 

 genera, the three recognized by Svetovidov (1948): 

 Enchelyopus. CUiata. and Gaidropsarus: and also 

 Onogadus de Buen 19.34; and a genus introduced 

 for the first time, Antonogadus. 



Onogadus was originally proposed for Gaidrop- 

 sarus ensis, one of the threebeard rocklings, be- 

 cause of its elongate first dorsal ray. Wheeler (in 

 Svetovidov 1973) has subsequently assigned to 

 Onogadus, G. argentatus, a species with a far 

 shorter first dorsal fin ray. We have found the 

 length of the first dorsal fin to be highly variable in 

 Enchelyopus. As presently used, this character 

 does not separate genera. (Wheeler^ has informed 

 us that Onogadus may be differentiated on the 

 basis of vertebral counts. Due to insufficient data 

 we have no comment on this character.) As we 

 have mentioned above, G. argentatus differs from 

 G. ensis and resembles Ciliata in lacking a median 

 supratemporal pore. 



'A. Wheeler. Department of Zoology. British Museum 

 (Natural History), Cromwell Road, London S.W. 7. England. 

 Pers. Commun. March 1978. 



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