12 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 124 



Anabas, and Pristolepis (fig. 26) hold in common certain peculiarities of 

 the caudal skeleton. In all three, there is the full percoid complement 

 of five hypurals (using Nybelin's [1963] system of counting) ; these are 

 all subequal in width and splayed out like the spokes of a fan. There is 

 only one epural, and the last hemal arch is not in contact with the 

 urostyle. (Judging from X-ray photographs [e.g., Liem, 1967, fig. 9], 

 Luciocephalus seems to have a specialized version of the same basic 

 type of caudal structure.) Finally, there is the fact that the Nandidae 

 and Pristolepidae, like the Anabantoidei, are freshwater fishes with a 

 distribution center in southeast Asia. 



The Percoidei and Derivative Suborders 



The suborder Percoidei comprises the central mass of the perciform 

 fishes; its members dominate the richer marine fish faunas today, 

 notably those of coral reefs. 



An ecological peculiarity that is at least worth noting is that many 

 of the percoid families that, on morphological grounds, seem to 

 stand at the base of the suborder contain or comprise euryhaline 

 and/or freshwater forms; e.g., the Centropomidae, Percichthy- 

 idae, Kuhliidae, Centrarchidae, Percidae, Nandidae. The same is 

 true of the "prepercoid" families Mugilidae, Atherinidae, Phallos- 

 tethidae, Ophicephalidae, Anabantidae, and Luciocephalidae. 



As compared with the presumably ancestral Beryciformes, the 

 percoids seem to differ in no one important character (Gosline, 1966b) ; 

 rather, judging by living forms, they appear to have integrated a 

 number of minor features in what amounts to an advance over the 

 Beryciformes in general adaptiveness. Again judging from the observa- 

 tion of living forms, the most satisfactory answer to the question of 

 wherein this advance lies seems to be in an increase in swimming 

 abilities in the percoids. 



On the other hand, if the suborders and orders derived from the 

 percoids are compared with the Percoidei, it becomes clear that each of 

 these derived taxa has adopted some specialized mode of life; thus, of 

 derivative percoid suborders, the xiphioids, scombroids, and schindl- 

 erioids have taken up an existence in the open sea, the gobioids and 

 blennioids have adopted a life in direct contact with the bottom, the 

 acanthuroids and stromateoids have developed specialized food habits, 

 etc. But, again, most of these specializations have involved further 

 changes in methods of swimming and maneuvering. Indeed, this 

 aspect of existence runs so continuously through the evolution of the 

 percoids and their derivatives that it seems well to take it up by way 

 of an introduction to these groups. 



The adult percoids are mostly maneuverers living close enough to 

 the bottom to use it for protection but not maintaining direct physical 



