Abstract
The skeleton and musculature of Trigonognathus kabeyai are described in detail. The particular jaw dentition suggests that Trigonognathus has a clutching-type feeding action. Several characters that might serve this function are discussed from the point of the functional morphology . The phylogenetic relationships of Trigonognathus are not fully resolved, but it possesses three of the four synapomorphies of the Etmopterinae, i.e., two separate labial cartilages, no supraotic shelf, and prespinal radials. Furthermore, three equally probable hypotheses of Trigonognathus relationships, a sister relationship with all etmopterine genera, Etmopterus+Miroscyllium, and Aculeola+Centroscyllium, are discussed.
