Ventrifossa rhipidodorsalis 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 535 m. It is found in 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...

, 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...

, the Philippines

Philippines

The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...

, and in the South China Sea

South China Sea

The South China Sea is a marginal sea that is part of the Pacific Ocean, encompassing an area from the Singapore and Malacca Straits to the Strait of Taiwan of around...

.

This species reaches a length of up to 21 cm. It can be distinguished from its congeners by the patterning of the fins: 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 mostly black with white at the base and tip, while the elongated anal fin has a black margin towards the front. There is a large bioluminescent organ located between the bases of the pelvic fins.