Scolecenchelys fuscogularis (Anguilliformes: Ophichthidae, Myrophinae), a new worm eel from Japan

A new species of worm eel (Ophichthidae, subfamily Myrophinae), Scolecenchelys fuscogularis, is described from two specimens collected at 90-147 m depth off the coast of Japan. The new species is characterized by its dorsal-fin origin, which is located posterior to a vertical through the anus, its high total number of vertebrae (146-149), and its uniserial dentition on jaws and vomer. The new species is similar to Scolecenchelys australis and Scolecenchelys tasmaniensis in having 148-152 total and 60-61 preanal vertebrae and its uniserial teeth, but can be distinguished from the latter two species as it has a larger head [8.5-8.8 % of total length (TL) vs. 7.8-8.3 %], a longer trunk (39 % TL vs. 34-35 %), and a shorter tail (52-53 % TL vs. 56-58 %). Although S. fuscogularis most resembles Scolecenchelys chilensis in having 146-159 total and 59-64 preanal vertebrae and uniserial teeth, as well as in the proportions of the head, trunk and tail, the new species differs from the latter in having a smaller head (8.5-8.8 % TL vs. 8.9-9.7 %), a more slender body (body depth 1.5-1.6 % TL vs. 2.3-2.9 %), a more posterior dorsal-fin origin (horizontal distance between the origin and a vertical through the anus 83 % of head length vs. 36-54 %), no groove on the ventral side of its snout, and a dark lower jaw with a patch of melanophores on the ventral side of its branchial basket.