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Zoology Publications from Victoria University of Wellington—Nos. 54 to 57

Relationship of Cirrhigaleus barbifer to Other Squalidae

Relationship of Cirrhigaleus barbifer to Other Squalidae

Tanaka's (1912) account of Cirrhigaleus and Herre's (1935) account of Phaenopogon (= Cirrhigaleus) as new genera did not include any indication of their views on the relationship to other genera in the Squalidae. Garman (1913, p. 457) in an addendum to his revision of elasmobranch fishes reduced Cirrhigaleus to a sub-genus of Squalus; he noted that "the mouth, teeth, scales, spiracles, and fins are those of that genus", and indicated that only the nasal barbel was distinctive. Fowler (1941, p. 262) followed Garman in treating Cirrhigaleus as a sub-genus of Squalus, but did so without comment. Bigelow & Schroeder (1948, page 8p. 451; 1957, p. 37) accepted Cirrhigaleus as a full genus despite its similarity to Squalus, and in a discussion in the later of these two accounts noted that this was justified by the "presence of the nasal barbel, combined with the lack of precaudal pits and of longitudinal-lateral ridges on the caudal peduncle".

Study of our specimens leads us to accept Bigelow & Schroeders' view that Cirrhigaleus deserves full generic rank even though the third generic character they cite cannot be upheld; Cirrhigaleus does have a ventrolateral keel on each side of the caudal peduncle and hence resembles Squalus in this respect. Other resemblances to Squalus are strong. Similarity in proportional dimensions is exemplified in Table 1, where for cursory comparison we have listed those of one specimen each of three Squalus species previously reported on by one of us (Garrick, 1960). The essential differences in proportions between Squalus and Cirrhigaleus are that the latter has a shorter snout and head, shorter but higher dorsal fins, and the 2nd dorsal fin is little smaller than the 1st, whereas in Squalus it is markedly smaller. Similarities between the two genera in the shape and structure of the mouth, teeth, dermal denticles and fins were noted by Garman (1913). We confirm these strong similarities, and would highlight that of the caudal fin in particular, but we observe that the dermal denticles of Cirrhigaleus are proportionately much larger—about twice as long—as those of comparably sized Squalus illustrated in Garrick (1960, p. 525, text-fig. 3). Meristic characters—dental formulae and vertebral numbers—differ little between the two genera (for vertebral numbers of Squalus species see Springer & Garrick, 1964).

Despite the above strong similarities there remains the fact that Cirrhigaleus differs from Squalus not only in possessing the remarkable nasal barbels which suggested its generic name but also in lacking completely the precaudal pits which are characteristic of Squalus. We believe that in combination these two characters reasonably justify the retention of Cirrhigaleus as a separate genus, though we would agree that in any subdivision of the Squalidae it would be necessary to place Cirrhigaleus closer to Squalus than to any other genus. It might be argued that the nasal barbels are foreshadowed in Squalus, especially in S. blainvillei and the S. megalops-cubensis group, where the anterior nasal flap is bilobed and the medial lobelet is in a comparable position to the nasal barbel of Cirrhigaleus. Even if this is the case, and the medial lobelet is homologous with the nasal barbel, the gross differences in the degree of development of the two structures merit recognition. In Squalus the medial lobelet is a minor structure, smaller than the lateral lobelet (= anterior nasal flap), and not reaching even to the posterior margin of the medial nasal aperture, whereas in Cirrhigaleus the nasal barbel is a major feature extending not only beyond the anterior nasal flap but far posteriorly along the snout.