Photo/IllutrationSatoshi Utsunomiya and a model of a spinosaurus (Erina Doi)

  • Photo/Illustraion
  • Photo/Illustraion
  • Photo/Illustraion

KAINAN, Wakayama Prefecture--A trip to buy “mikan” oranges led to the third discovery in Japan of a tooth fossil from a spinosaurus, a fish-eating dinosaur that was among the largest carnivores.

The fossilized tooth dates back to the first half of the Cretaceous period around 130 million years ago. It is one of the oldest fossils from a spinosaurus unearthed in Asia, according to the Wakayama Prefectural Museum of Natural History.

According to the museum’s announcement, the fossil was discovered by Satoshi Utsunomiya, 49, a company employee and fossil hunter from Higashi-Osaka, Osaka Prefecture.

When Utsunomiya visited Wakayama Prefecture to buy mikan in October, a stone on a road caught his attention in a coastal area in Yuasa.

After breaking the stone, Utsunomiya realized that a dinosaur fossil was inside.

The 14-millimeter-long cone-shaped fossil of the tip of a tooth has a vertical stripe pattern and a thick enamel layer. It was later identified as part of a spinosaurus.

A fossilized tooth of a different carnivorous dinosaur was discovered in the same coastal region in 2007.

The latest fossil was donated to the Wakayama museum, which worked with Yasuhisa Nakajima, an associate professor of vertebrate paleontology at Tokyo City University.

A museum official said the latest discovery is very important because it supports the theory that different species of dinosaurs were separated on the south and north sides of the Median Tectonic Line, which cuts across the Japanese archipelago, in the early Cretaceous period.

Two other spinosaurus fossils have been found in Japan, both in Gunma Prefecture. Gunma and Wakayama prefectures are both located on the south side of the line.

Many dinosaur fossils have been discovered in Fukui Prefecture, which is north of the line, but no spinosaurus fossils have been found there.

The Wakayama museum will put the latest tooth fossil on display between June and September.

The spinosaurus, characterized by a sail-like dorsal fin, is said to have measured up to 15 meters long and was a good swimmer. It was featured in “Jurassic Park III” in 2001.