Following the publication of five species of Symphurus from the shallow waters of the western Pacific Ocean in 2021, the Fisheries Research Institute discovered a new species of deep-sea Symphurus. The new species, named the Sharpnose Tonguefish (Symphurus oxyrhynchus) due to its squarish sharp snout, was published in September 2022 in the international taxonomic journal Zootaxa.
According to the Fisheries Research Institute, Symphurus is a group of small to medium-sized flounders that do not have lateral lines, and taxonomically belongs to the Cynoglossidae family, which are commonly known as the sole fish of the ox-tongue and dragon tongue fishes. Symphurus is widespread in tropical to temperate waters worldwide, and inhabits depths ranging from shallow water to 1,500 m deep. Including Symphurus oxyrhynchus, there are currently 87 species of Symphurus globally, 10 of which were named by Dr. Mao-Ying Lee, who is currently working at the Fisheries Research Institute.
Symphurus oxyrhynchus has a distinctive 1-2-2-1-2 dorsal fin insertion (ID pattern) and a 3+6 body vertebrae pattern, which is unique to S. macrophthalmus from the Indian Ocean and S. shultzi from the Philippines; however, Symphurus oxyrhynchus differs from these two species in the number of dorsal and anal fin rays, the total number of vertebrae, the size of the eyes, the length of the head, and the snout pattern, among other characteristics.
According to the Fisheries Research Institute, Symphurus oxyrhynchus is a rare species and only two specimens have been recorded. Dr. Mao-Ying Lee visited various museums in Taiwan and Japan to examine the specimens and noted the morphological differences between them and other Symphurus, thus, confirming that the two specimens are new species of Symphurus. The two specimens were collected from Tosa Bay, Japan, and Liuqiu Island, Taiwan, at depths ranging from 718 m to 852 m, respectively, and were caught by a trawler of the research vessels. Compared with the sampling depth of the research vessel, the deep-sea bottom trawlers can only operate at depths as shallow as 600 m, and the catch of deep-sea fishes is limited to the species distributed at depths ranging from 200 m to 600 m. Thus, it is necessary to rely on research vessels to conduct more comprehensive surveys in the deep sea around Taiwan to further understand the population size, ecology and distribution, and other related data of Symphurus oxyrhynchus in the future.
Figure. specimen photographs of Sharpnose Tonguefish (Symphurus oxyrhynchus) the holotype specimen from Tosa Bay, Japan (A) and the paratype specimen from the southern waters of Little Liuqiu, Taiwan (B)