FISHERY BULLETIN: VOL. 72, NO. 4 



mouth that has given rise to the enormous variety 

 of specialized feeding mechanisms for which tele- 

 osts are so v^ell known. Presumably, the evolution 

 of the acanthopterygian jaw mechanism promoted 

 the successful exploitation of food sources that 

 previously were largely unavailable to actinop- 

 terygian fishes." They referred to the protrusible 

 premaxillary of acanthopterygians, which per- 

 mits them to project their upper jaw at food. Fishes 

 with this mouth construction can accommodate 

 the shape and size of the mouth opening more 

 appropriately to the shape of the food item than 

 can fishes without a protusible premaxillary 

 (Alexander, 1967; GosHne, 1971). 



During the Cretaceous, in which the be- 

 ryciforms flourished, the ecological role of the 

 scleractinian corals was challenged by a group of 

 bivalved mollusks, the rudists, which underwent 

 an extraordinary radiation and became the center 

 of a highly successful and widespread reef com- 

 munity. But at the end of the Cretaceous, about 70 

 million years ago, these and other reef com- 

 munities collapsed in sweeping extinctions as- 

 sociated with the worldwide biological revolution 

 that marked the close of the Mesozoic (Newell, 

 1971). 



Tertiary seas over most of the world were with- 

 out known coral-reef communities until litho- 

 thamnion-scleractinian reefs underwent a second 

 major radiation during the Eocene, about 50 mil- 

 lion years ago (Newell, 1971). The communities 

 that developed in association with these reefs are 

 essentially those of our time. And in what would 

 seem a related phenomenon, the explosive radia- 

 tion of acanthopterygians into the types that in- 

 habit modern reefs also occurred during the 

 Eocene (Patterson, 1964). Of the families living on 

 reefs today, only a relatively few can be traced 

 back in time earlier than the Eocene (Berg, 1940), 

 and yet by the end of that period, which spanned 

 about 15 million years, representatives of almost 

 every major type of modern fish had appeared 

 (Romer, 1966). 



This most recent proliferation of acanthop- 

 terygians probably radiated from a line of 

 generalized percoidlike carnivores that had arisen 

 from among the Beryciformes during the late Cre- 

 taceous (Gosline, 1966). Above, I note that 98.5% 

 of the fishes seen on Kona transect lines are acan- 

 thopterygians; more specifically, 90.4% are acan- 

 thopterygians that have reached, or passed, the 

 percoid level of structural development, and 

 75.5% belong to the order Perciformes (see foot- 



note 7). Only the holocentrids represent the ances- 

 tral Beryciformes. In fact, worldwide the Holocen- 

 tridae, and a few species of Anamalopidae, are the 

 only representatives of this once prolific order that 

 have survived on nearshore reefs. 



Obviously the percoid level of development has 

 been highly successful. Gosline ( 1971 ) pointed out: 

 ' In no single way does it seem to differ from that of 

 the now unimportant, perhaps relic Beryciformes 

 from which it was presumably derived. Possibly 

 the percoids have developed some distinct and as 

 yet unknown biological advantage over the Be- 

 ryciformes, but for the moment one can only as- 

 sume that the percoids represent a successful 

 integration of minor advances." The minor ad- 

 vances which Gosline cited include increased 

 maneuverability and adaptability of the protrusi- 

 ble jaw mechanisms, which are refinements on 

 those same features adaptive to reef living that 

 probably gave the Beryciformes an advantage 

 over their progenitors. 



Generalized Carnivores: 

 Main Line of Teleostean Evolution 



From early Mesozoic times the main line of ac- 

 tinopterygian evolution has progressed through a 

 series of generalized carnivores; with each step 

 forward, the basic feeding mechanism has im- 

 proved, and the potential for adaptive radiation 

 has increased (Schaeffer and Rosen, 1961). Al- 

 though this progression has been marked by 

 periodic bursts of specialized offshoots, the pri- 

 mary stem, the generalized carnivore, has re- 

 mained relatively conservative (Gosline, 1959). 



The generalized predator, in simplified form, 

 has a large mouth and is adapted to directly ap- 

 proach, and seize,' prey that are fully exposed to 

 the attack. Its prey are small enough to be ma- 

 nipulated, yet large enough to be grasped; 

 moreover, the prey are not sealed in heavy ar- 

 mour, nor do they carry strong spines, spicules, or 

 other noxious components for which the un- 

 specialized digestive tract of the generalized pred- 

 ator is maladapted. Although even the most 

 primitive of today's predators have acquired at 

 least some feeding specializations, the closer one 

 approximates this simplified form, the closer its 

 feeding habits fit this description. 



With the generalized predaceous feeding 

 mechanism being a relatively conservative mor- 

 phological link between periods of adaptive radia- 

 tion in actinopterygian fishes, one would expect 



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