Photo/Illutration Ryohei Nakagawa, a curator at the Mie Prefectural Museum in Tsu, poses for a photo Aug. 21 with the dolphin head fossil determined to be a new species 33 years after it was discovered. (Makoto Takada)

TSU, Mie Prefecture--A fossil discovery by Yoshihiko Saka when he was a schoolboy 33 years ago was likened to “winning the jackpot” after museum officials here belatedly realized it represents a new dolphin species.

Because the fossil was encased in calcium deposits, it languished untouched in storage at the Mie Prefectural Museum, even after the facility moved to a new site in Tsu in 2014.

Two museum curators who eventually got around to gingerly cleaning the fossil and removing the calcium deposits published their findings in August in a scientific journal issued by the Natural History Museum in London.

Saka was a fifth grader at the Kameyama city-run Kameyama-Nishi Elementary School when he made the discovery in 18-million-year-old stratum from the early Miocene epoch in the city’s Ichishicho district in July 1991.

The museum hosted an event the following month to give names to fossils found in the area. Based on the protruding part of the upper jaw bones, museum officials determined the item brought in by Saka was a dolphin’s head and asked him to donate the fossil for its collection.

TOUGH CLEANING JOB

In 2017 or 2018, Ryohei Nakagawa, a curator at the Mie Prefectural Museum specializing in fossils of small mammals, approached Yoshihiro Tanaka, a curator at the Sapporo Museum Activity Center in Hokkaido who is well-versed in the evolution of whales, telling him there was a specimen worth examining.

When Tanaka visited the Mie museum, he was amazed to find a near-complete head.

As a starter, the duo started removing rock and other debris from the fossil in 2021.

After scraping off the calcium deposits, they began examining it through a microscope using pen-shaped air scribes with a vibrating needle-like tip.

They also coated the rock in plastic resin and took other steps to dissolve its surrounding parts with acid.

That process alone took nearly two years to complete.

What emerged was the head of a dolphin about 30 centimeters long, which had 4-cm-long ear bones, eye and nose sockets, teeth and other skull parts.

Because dolphins use ultrasonic waves to sense their surroundings, their ears are characterized by complicated structures.

The fossil bore no similarities to other dolphin fossils, so it was determined to be from a new genus and species.

Nakagawa dated the fossil based on the distribution of the stratum in which it was found.

The dolphin was given the scientific name of Miodelphinus miensis, which means “a dolphin from Mie's Miocene epoch” (between roughly 23 million years ago and 5 million years ago). Its Japanese name is “Mie Iruka” (Mie dolphin).

The museum said it is closely related to the endangered Ganges river dolphin in India.

FOR POSTERITY

Saka, now 43 years old, works for a company.

He became interested in paleontology when he was in third- or fourth-grade after he found a sea snail fossil in Shiga Prefecture while picking wild vegetables.

“I had always wondered what it really was,” he recalled. “I never thought it was a new species. I was surprised.”

Nakagawa said, “The probability of finding a new species is the same as the probability of winning the jackpot in a lottery. We’d like to thank Mr. Saka.”

Tanaka added: “Our duty as a museum is to pass specimens down to the next generation, sort of like handing over the baton, to create good encounters between specimens and researchers. We hope our latest world-class discovery will serve as an opportunity to hand over the baton of dolphin research to a new generation of studies.”

Related News