Hemitriakis falcata n.sp. and H. abdita n.sp., two new houndsharks (Carcharhiniformes: Triakidae) from Australia

Abstract

Two new species of the genus Hemitriakis Herre, 1923 (Carcharhiniformes: Triakidae) are described from tropical Australia. Hemitriakis falcata is described from ten specimens from the outer continental shelf of Western Australia at depths of 146 to 197 m. Hemitriakis abdita is described from five specimens from the Coral Sea Plateau off north-eastern Queensland at 225 to 401 m. Hemitriakis falcata and H. abdita are separable from their two named congeners H. leucoperiptera, from the Philippine Islands, and H. japanica, from Japan, Taiwan, China and Korea, by a combination of vertebral counts, first dorsal position, fin and eye shape, and juvenile colouration. Hemitriakis falcata additionally differs from H. japanica in chondrocranial morphology. Hemitriakis falcata and H. abdita are sibling species separated by wide, non-overlapping differences in vertebral counts as well as by slight differences in morphometrics, tooth counts, colouration, and cranial morphology. These species represent the first record of Hemitriakis from Australia. A nominal record of H. japanica from Ambon is uncertain while another record of H. japanica from New Caledonia may be based on H. abdita. A key to species of Hemitriakis is presented.