Marine biologists have discovered a new species of the shark genus Squalus in the tropical waters off southern Japan.
The Shirai’s spurdog (Squalus shiraii): lateral (A-C) and ventral (D, E) views. Scale bars – 50 mm. Image credit: Viana & Carvalho, doi: 10.3897/zse.96.51962.
Squalus is a genus of dogfish sharks in the family Squalidae, which is part of the order Squaliformes.
Commonly known as spurdogs, these sharks are commercially important species within the world fish trade, in which individuals are caught through direct or indirect fisheries and traded for consumption of meat, fins and liver oil as primary products.
Over 30 species are currently recognized in the genus, of which at least six inhabit Japanese waters.
“Despite their high occurrence, the accurate identification data of species is scarce, population threats and trends remain unknown,” said Dr. Sarah Viana from the South African Institute for Aquatic Biodiversity and Dr. Marcelo de Carvalho of the Universidade de São Paulo.
In a new study, the researchers revised the nominal Squalus species occurring in the region.
“The new species was long misidentified with the shortspine spurdog (Squalus mitsukurii), due to the same shape of body, fins and snout length,” they explained.
“However, morphological, meristic and morphometric evidence support it to be a separate and undescribed species.”
Named the Shirai’s spurdog (Squalus shiraii), the new shark has an elongated body between 59 and 77 cm (1.9-2.5 feet) long.
The species is apparently a Japanese endemic, occurring in the shallow waters of the upper continental slope off Southern Japan in the North-western Pacific Ocean at 310-390 m (1,017-1,280 feet) depth.
“The Shirai’s spurdog differs from the shortspine spurdog by having body brown in color dorsally, caudal fin with ventral and dorsal tips markedly tapered and broadly white, dermal denticles uniscuspidate and lanceolate and larger number of precaudal and total vertebrae,” the scientists said.
The discovery is reported in a paper in the journal Zoosystematics and Evolution.
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S.T.F.L. Viana & M.R. Carvalho. 2020. Squalus shiraii sp. nov. (Squaliformes, Squalidae), a new species of dogfish shark from Japan with regional nominal species revisited. Zoosystematics and Evolution 96 (2): 275-311; doi: 10.3897/zse.96.51962