The tooth, which is somewhat pencil shaped with a rounded tip comes from a type of sauropod called a titanosaur. Scientists at the Fukui Prefectural Dinosaur Museum examined the tooth and noted similarities to the teeth of Fukuititan from Honshu, Japan's largest island. Titanosaurs were widespread in the Cretaceous and include the largest of all dinosaurs like Argentinosaurus and Dreadnoughtus, although the owner of the tooth was quite a bit smaller, probably measuring only about ten meters from nose to tail tip.
This new fossil find increases the diversity of dinosaurs known from Japan, and specifically from Shikoku. Previously, only indefinite remains of ornithopod dinosaurs were known from Early Cretaceous rocks; and indeterminate remains of ornithopods and sauropods were known from Late Cretaceous rocks on Shikoku.
Original story published on The Asahi Shimbun.