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Found in Aomori Prefecture, the fossil had been believed to come from the Palaeoloxodon naumanni, commonly known as the Naumann elephant, which roamed Japan 20,000 to 300,000 years ago.
Recent analysis using advanced technology revealed the fossil, in fact, belonged to a much older mammoth species that was here between 700,000 and 1.1 million years ago.
The tooth, measuring about 17 centimeters long and 7 cm wide, is believed to be a molar from the right side of the mandible. It had been on display at Aomori Prefectural Museum here, on the northern tip of Japan’s main island of Honshu, since 2005 labeled as of the Palaeoloxodon naumanni.
The fossil was caught in a dragnet by a scallop fisherman about 300 meters offshore of a wharf in Mutsu Bay, Mutsu city, in December 2004. The fisherman donated the finding along with another fossil believed to be an incisor tooth that he also found in the same area about 10 years earlier.
According to Takashi Shimaguchi, 49, the vice chief of the prefectural museum’s curation department, identification of elephant teeth is usually done based on the pattern on their surface. However, the donated fossil was too worn, and it was difficult to make a conclusive identification.
In 2005, the museum published a paper that identified it as a molar of the Naumann elephant after asking an external researcher to identify it. It had been displayed as such at the museum since then.
Later, more than one elephant fossil expert pointed out that the tooth is more likely to be of the Mammuthus protomammonteus, an ancestor of the woolly mammoth that inhabited the region from 700,000 to 1.1 million years ago. However, confirming the molar’s true identity was no easy task.
In 2016, CT scanning of the fossil was conducted at a Tokyo facility to examine the layer of enamel below the surface. The scan revealed it was much closer to that of a mammoth.
The time period it dates from also matches the age of the strata near where it was found.
“To be honest, I am relieved now the matter is settled thanks to new technology, even though it took a long time to conclude,” said Shimaguchi. “As it is the first to be found in the Tohoku region, I would be happy if it leads to new research.”
According to Keiichi Takahashi, an expert on elephant fossils who was involved in the re-examination of the molar, the Mammuthus protomammonteus moved to Japan from the Asian continent during a colder period when sea levels were lower.
Fossils of Mammuthus protomammonteus teeth and tusks have been discovered at about 30 locations around Japan so far, but no bones have been discovered, making it difficult to deduce the creature’s body size. It is believed that they were about the same size as today’s Asian elephant (about 2.5 meters tall) based on the size and shape of teeth found, and the climate of that period.
When the mammoth appeared in Japan 1.1 million years ago until they perished 700,000 years ago, the climate remained stable and was similar to that of the present day.
The mild climate means they were likely to have had short hair and fed on low-growing grass.