A new species of Elassodiscus (Cottoidei: Liparidae) from the North Pacific with an emended diagnosis of the genus

A new snailfish, Elassodiscus nyctereutes, previously confused with Elassodiscus caudatus, is described on the basis of genetic evidence and morphometric and meristic analysis of 55 specimens. The new species is most similar to E. caudatus in having a greatly reduced pelvic disk, two suprabranchial pores, trilobed teeth, and long pectoral-fin rays in the lower lobe that reach to the anal-fin origin. However, the new species is clearly distinguished from the latter by having more vertebrae (67–75 vs. 56–60), dorsal- (59–69 vs. 51–54), and anal-fin rays (52–63 vs. 45–50). The two species are parapatrically distributed in the North Pacific: E. nyctereutes is widely known from the southern part of the Sea of Okhotsk, off Rausu, eastern Hokkaido, Japan; the Pacific Ocean off Kamchatka and the Kuril Islands; the Aleutian Islands; and the Bering Sea at depths of 362–1,200 m; whereas E. caudatus is only known from the eastern North Pacific, from the eastern Gulf of Alaska to California at depths of 335–925 m. We also provide an emended diagnosis of the genus Elassodiscus, as well as a key to the known species.