Japan’s First Tyrannosaurid Bones Excavated; Lower Jaw Fragments Found in Kumamoto Pref.

The Yomiuri Shimbun
Fossilized tyrannosaurid’s lower jaw bones in Amakusa, Kumamoto Prefecture, on Thursday

AMAKUSA, Kumamoto — Fossilized lower jaw fragments from a tyrannosaurid, which belongs to the same family as the Tyrannosaurus, have been excavated in the Amakusa Islands in Kumamoto Prefecture, according to two museums that have conducted research on the discovery

The Amakusa municipal Goshoura Cretaceous Museum in Kumamoto Prefecture and the Fukui Prefectural Dinosaur Museum in Fukui Prefecture announced Thursday in Amakusa that they discovered the fragments in Reihoku, a town on Shimoshima Island in the Amakusa Islands. The parts were found in the Late Cretaceous strata, dating it back approximately 74 million years.

The museums said that this was the first time that fossilized bones of a tyrannosaurid have been found in Japan, though fossilized teeth have been found in the past, suggesting that the discovery will likely be important for understanding large carnivorous dinosaur habitats in Asia.

The fossilized parts were excavated during a survey conducted in 2014 by the museums, which examined them using CT scans to determine that they were parts of a dentary bone, a section of the lower jaw that supported the teeth. The museums identified the bones as belonging to a tyrannosaurid, judging from the characteristics of the remaining teeth, which were large and had a distinctively elliptical cross-section.

Left- and right-side dentary parts were found together, with the left side measuring 14 centimeters long and 8 centimeters thick, and the right side 17 centimeters long and 8 centimeters thick.

The dinosaur is estimated to have been over 8 meters long.