For the first time in Japan, fossils of multiple kinds of theropods have been found in the same stratum or area, following the discovery made in Kuji, Iwate Prefecture, the Kuji Amber Museum among other groups have announced earlier this month.
The fossils in stratum from the late Cretaceous period dating back about 90 million years were found by the team including Waseda University Prof. Ren Hirayama. The tooth of a carnivorous dinosaur related to tyrannosaurs had been discovered in Kuji before.
The discovery was made in the city's Tamagawa Formation of the Kuji Group, where more than 2,300 fossils of turtles, crocodiles and other vertebrates have been unearthed so far. The stratum is regarded as important for understanding the ecosystem during the dinosaur era in Japan.
The newly discovered fossils are teeth from three theropod species and measure about 3 millimeters to 1 centimeter in size. A total of five fossils have been unearthed from 2016 through this year. Among them are teeth from a small dinosaur called Richardoestesia about 1.5 meters in length. Fossils from this species have been found in late Cretaceous strata in North America, but these are the first to not only be found in Japan, but in all of Asia, the museum said.
According to paleontology expert Hirayama, as fossils were found both with serrated teeth -- a characteristic of carnivorous dinosaurs -- and without in the same stratum, it shows that dinosaurs back then were a mixture of carnivores and omnivores. In addition, the discovery of several kinds of theropods, which sat at the top of the food chain, suggests that the Kuji region of that era had a rich ecosystem.
"Few fossils of Richardoestesia other than teeth have been found, but we have hopes of finding other parts in Kuji," Hirayama said at a press conference in Tokyo on July 9.
Daito Ishiga, a 19-year-old sophomore at TCA Tokyo College of Eco & Animals' Dinosaur and Natural History Course, who discovered the Richardoestesia teeth, said, "I was thrilled to learn that they were dinosaur teeth. I'm honored to have made the discovery."
The newly found fossils will be on display at a special exhibition in the Kuji Amber Museum in Iwate Prefecture through Sept. 26. It is open from 9 a.m. to 5 p.m. (last entry 4:30 p.m.). Admission is 500 yen for high school students or older and 200 yen for elementary and junior high school students.
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