Eggshell fossils believed to be related to the small carnivorous dinosaur Troodon were found in the Mesozoic stratum in Shokawa-cho, Takayama City, Gifu Prefecture.This was confirmed by a research team consisting of Kohei Tanaka, an assistant professor in the Faculty of Life and Environmental Sciences at the University of Tsukuba, and Shohei Takatsu, a curator at the Gifu Prefectural Museum.Troodontidae specimens have been found only in China in Asia, and are an important record for understanding their distribution.

 According to the University of Tsukuba, the eggshell fossils were found in the early Cretaceous stratum in the Shokawa region of Takayama City, part of the Tedori Group, which is widely distributed in the Hokuriku region and where numerous dinosaur fossils have been excavated. Kurodani Formation (approximately 1-2900 million years ago).From 1 to 3300, in the Daikokudani Formation, fossil bones of various vertebrates such as dinosaurs and turtles, as well as a total of nine eggshell fossils were collected. It was found to contain the eggshell fossils of a theropod dinosaur thought to belong to the Troodontidae family.

 It is the oldest eggshell fossil discovered in Japan, and the second example of an eggshell fossil believed to belong to the Troodontidae family, after Hyogo Prefecture.In addition, it was identified as a new egg genus and new egg species because it has a characteristic surface pattern not found in other eggshell fossils of the Troodontidae family.It was named "Ramoprismatouritus ookurai" after Masatoshi Okura, who was the first to discover eggshell fossils in the Shokawa region.Judging from the thickness of the shell, the egg is slightly larger than a chicken egg, weighing about 2g, and is thought to have been laid by a small Troodontidae.

 Troodontids are one of the groups closely related to birds, and were carnivorous and omnivorous, with large claws on their hind limbs.It is believed to have emerged in Asia during the Early Cretaceous and thrived in the northern hemisphere.Ramoprismatouritus ookrai is the easternmost discovery of a small theropod fossil about 1 million years ago, and it can be said that it is an important record in terms of age and geographical distribution.

Paper information:[Historical Biology] Fossil eggshells from the Early Cretaceous Okurodani Formation, northern central Japan

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