Specialization of the gobioid palatopterygoquadrate complex and its relevance to gobioid systematics

Abstract

The gobioid suspensorium provides a suite of characters which seem valuable in hypothesizing gobioid phylogenies. Characters presently discussed refer to the architecture of the palatopterygoquadrate complex; i.e., the structure of the palatine, ectopterygoid and quadrate, and the spatial relationships existing between these bones. Several genera exhibit specialization, to different levels, of the palatopterygoquadrate complex. The following are regarded as specialized characters: a long palatine extending towards, or meeting the quadrate; or a very short, stubby palatine; a shallow ectopterygoid meeting the anteroventral corner of the quadrate, near the articulation with the lower jaw; a quadrate which is deeply forked, bearing an anteroposteriorly short dorsal lamina with a long anteroventrally sloping edge. Examination of the distribution of these palatopterygoquadrate complex characters, and reference to other, previously documented, features of gobioid skeletons and modified lateral-line systems, permits discussion of the phylogeny of several gobioid genera. The Gobionellinae, the Sicydiinae, and Awaous exhibit specialized characters of the palatopterygoquadrate complex, and are hypothesized to form a monophyletic group. Affinities between these lineages and the Microdesminae are also proposed, on the basis of similarities in palatopterygoquadrate complex, and other morphological characters.