Akira Ota holds the fossil of what was determined to be a new fish species, after commenting, “I was excited when I thought it might be a new species,” at the Hobetsu Museum in the town of Mukawa, Hokkaido, on April 9, 2025. (Mainichi/Kimitaka Hirayama)
MUKAWA, Hokkaido — A fossilized tooth of a cartilaginous fish found in Japan’s northernmost prefecture Hokkaido in 2013 is of a newly discovered species, researchers announced here on April 9.
The fossil, found in the town of Mukawa’s Hobetsu district, is said to be the first known case in the North Pacific for a member of the genus Callorhinchus, which includes today’s elephant fish. The discovery was announced by Mukawa’s Hobetsu Museum and the Hokkaido University Museum in Sapporo.
The upper jaw tooth, about 3.2 centimeters long and 1.5 cm wide, was found by Sapporo-based researchers in a stratum dating back roughly 72 million years. It was then donated to the Hobetsu Museum, where municipal employee Akira Ota and others further researched it.
Unlike sharks whose teeth are replaced periodically, members of Callorhinchus have two pairs of platelike teeth in the upper jaw and one pair in the lower jaw. This fossil tooth exhibited a pawlike bulge unique to the genus. Further examination revealed that the shape of the bulge had a characteristic not seen in either present or previously known extinct species, leading it to be named a new species, Callorhinchus orientalis. The findings were published in Paleontological Research, the English journal of the Palaeontological Society of Japan.
The fossil of a tooth from newly-named fish species Callorhinchus orientalis is seen in Mukawa, Hokkaido, on April 9, 2025. (Mainichi/Kimitaka Hirayama)
After graduating from Hokkaido University, Ota served two years in regional revitalization in the town from 2015 and later focused his master’s thesis on fossils excavated in Hobetsu. In 2019, he was hired by the town as a general staff member and continued his research on Callorhinchus.
Joint author Yoshitsugu Kobayashi, a paleontologist and professor at the Hokkaido University Museum, said, “Mukawa is known as ‘Dinosaur World,’ but both sea creatures and dinosaurs washed out to sea (such as Kamuysaurus) were found in the same stratum. New animals may yet be found.”
The fossil is on display in a mini-exhibition at the Hobetsu Museum from April 10 to Aug. 31.
(Japanese original by Kimitaka Hirayama, Tomakomai Bureau)
AloJapan.com