Ischyodus bifurcatus, a new speciesof chimaeroid fish from the upper cretaceous of New Jersey

Abstract

Toothplates of the ratfish Ischyodus are rather common fossils, distributed throughout the Campanian-Maestrichtian of New Jersey and Delaware although heretofore unrecognized or described. A new species of Ischyodus differs from the European species, I. thurmanni Pictet & Campiche and I. dolloi Leriche, by the fusion of the median and internal posterior tritors of the mandibular apparatus. Except in rare individuals the palatine elements of I. bifurcatus do not show any fusion of their tritoral aspects. The vomerine elements show no distinctive features that could separate them from of any of the known Ischyodus species, and the dorsal fin spine is not significantly different from those of other known chimaeroid fishes, including Edaphodon, Elasmodus, Elasmodectes and Leptomylus. Ischyodus bifurcatus is erected as a new species based upon the bifurcated appearance of the fused mandibular tritors. A temporal range from late Santonian to medial Maestrichtian is indicated by occurrences in Belgium, California, Montana, Arkansas, and Delaware as well as New Jersey.