Infraorbital bones and their bearing on the phylogeny and geography of osteoglossomorph fishes. American Museum novitates ; no. 2394

Abstract

"The primitive condition of the teleostean infraorbital series probably included seven separate bones from the antiorbital to the dermosphenotic. The anterior four bones probably enclosed more than one neuromast each, but the posterior three bones probably enclosed only one neuromast each. Reduction both of bone and neuromast numbers seems to have occurred during the evolution of most teleostean groups. The primitive condition of seven infraorbital bones occurs in at least some members of all major teleostean groups except the Osteoglossomorpha. It is suggested that the osteoglossomorph condition, typically of six or fewer bones, has resulted from secondary fusion between two of the middle bones of the series. Infraorbital and other evidence, primarily the structure of the caudal fin, indicate that the Recent Osteoglossomorpha constitute a monophyletic group, and suggest certain interrelationships among the members of that group. Nevertheless, some interrelationships remain problematical. For this reason a satisfactory phyletic classification of the Osteoglossomorpha and a comprehensive theory of their geographic history are not yet attainable"--P. 31-32.