This fossil was discovered by chance by a visitor who was experiencing mining in June 2018.At the amber mining experience site, the Kuji Group Tamagawa Formation (late Cretaceous, about) distributed around this area, such as the almost complete shell of turtles, the hipbone of small herbivorous dinosaurs, and part of the wings of pterosaurs. Fossils of terrestrial vertebrates sleeping 6 million years ago have been discovered one after another.

　The tooth fossil discovered this time was identified as a premaxillary tooth of Tyrannosauroides because of its unique characteristics such as a D-shaped cross section and a bulge in the central part of the lateral surface of the tongue.From the size of the teeth, the total length of this dinosaur was estimated to be around 3m.

　In Japan, eight fossils of tyrannosaurus have been reported so far, and three of them have been reported as reliable materials such as premaxillary teeth (Fukui prefecture, Ishikawa prefecture, and). Hyogo Prefecture).Since all of these three premaxillary teeth were fossils from the Early Cretaceous, the fossils discovered this time were the first reliable Tyrannosaurus in the Late Cretaceous in Japan.

　The Tyrannosaurids include the Late Cretaceous Tyrannosaurid (including the so-called T-Rex) and the Proceratosaurid (a more primitive and smaller group) that prospered from the Jurassic to the Early Cretaceous. Detailed affiliation is undecided.Since there are no serrations on the incisal edge of the tooth, it is possible that there is a possibility that the details of the tyrannosaurus are unknown, and future studies and the discovery of additional materials are expected.

reference:[Waseda University] Found in Kuji City, Iwate Prefecture Tyrannosaurus tooth fossils