Thesis

Systematics of the genus Echinorhinus Blainville, based on a study of the prickly shark Echinorhinus cookei Pietschmann

The genus Echlnorhlnus Blainville contains two species, the brambleshark E, brucus. first described by Bonnatere (1788), and the prickly shark E, cookel. first described by Pietschmann (1928), Due to the considered a variant of E. brucus (Fowler, 1941), Garrick (1960), however, redescribed E, cookei and showed that it deserved recognition as a separate species. He found that, the distinction of E. cookel from E, brucus is definite and striking, at least between sub-adult specimens, but so far can be based only on the buckler-like dermal denticles. There appear to be no significant differences in proportional dimensions, in external morphology, or in details of the teeth. However, the differences in the denticles lie not only in their relative size as mentioned above, though this alone is sufficient, but also in the shape and sculpture of the denticle bases (entire-margined or nearly so, and with rather fine radial ridging in E. brucus. but with strongly indented margins and coarse ridges in E. cookel); the presence in E. brucus of compound denticles up to 35 mm long as a result of fusion of adjacent denticle bases, while such fused denticles are not a feature of E. cookei; and there is the tendency in E. brucus to retain noticeable-sized denticles on the underside of the snout and around the mouth even on large specimens, while in the type of E. cookei and in my specimen this area is virtually smooth, only a few minute denticles being present. Garrick also noted that many past records of E. brucus could have been records of E. cookel. for example, the account of an E. "brucus" given by Hubbs and Clark (1945). This specimen was subsequently found to be E. cookei.

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