550 



ONTOGENY AND SYSTEMATICS OF FISHES-AHLSTROM SYMPOSIUM 



Fig. 297. Larvae of (upper) Luvarus imperiatis, 6.8 mm TL, modified after Fahay ( 1 983); and (lower) Zanclus canescem. 16 mm SL. modified 

 after Strasburg (1962). 



but only the third dorsal spine is elongate (the unknown smaller 

 larvae may have elongate spines in other fins). 



Relationships 



Acanthuroids share the following, probably derived charac- 

 ters (we assume acanthuroids have a percoid ancestry): long 

 pelagic period; early-forming, elongate dorsal and pelvic spines; 

 serrate fin spines; moderately to very deep, compressed body; 



serrate ridges on the head; silvery gut; 22-23 vertebrae; and 16- 

 1 7 principal caudal rays. This is strong evidence for the 

 monophyly of the group. 



Tyler (1970) notes that acanthuroids have been considered 

 as chaetodontid derivatives. We find no support for this view 

 among ELH characters. Chaetodontids and pomacanthids do 

 have large, specialized pelagic stages, but these differ greatly 

 from acanthuroids (Leis and Rennis, 1983) and resemble ca- 



