Ventrifossa saikaiensis is a species of rattail

Rattail

Grenadiers or rattails are generally large, brown to black gadiform marine fish of the family Macrouridae...

. This is a deep-water fish found at depths of up to 740 m. It is found in the waters off southern Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

 and northern Taiwan

Taiwan

Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...

.

This species reaches a length of up to 25 cm. It has a pointed snout, a large, inferior mouth with a dark margin on the upper lip and a long chin barbel

Barbel (anatomy)

A barbel on a fish is a slender, whiskerlike tactile organ near the mouth. Fish that have barbels include the catfish, the carp, the goatfish, sturgeon, the zebrafish and some species of shark...

. The first dorsal fin

Dorsal fin

A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...

 is entirely dark, lacking the contrasting patches seen in some members of the genus. There is a large bioluminescent organ located between the bases of the pelvic fins.