Bulletin of the Mizunami Fossil Museum

Bulletin of the Mizunami Fossil Museum No. 4

A fossil skeleton of elasmobranchs was found from the Yamanouchi member, Akeyo formation, Mizunami group, Middle Miocene, at Yamanouchi, Akeyo-cho, Mizunami City.

This specimen is composed of many elongate cartilages and several vertebrae and teeth. The teeth are identified to Squatina sp. by mean of their morphological characters. The vertebrae have a concentric circle structure on their cross section surface, which is seen in the vertebrae of squaloid elasmobranchs, especially genus Squatina. The form of the cartilages resembles to the palatoquadrate, Meckel's, hyoid and hyomandibular cartilage and other gill cartilages of elasmobranchs. On the surface of these cartilages, a granular structure, which is seen on the surface of the calcified cartilage in recent elasmobranchs, is observed.

According to these special features, this specimen can be identified to the skeleton of elasmobranchs, particularly genus Squatina.