Abstract
The Middle Jurassic Mitarai Formation distributed in Shokawa Village, Gifu Prefecture, central Japan, is interpreted as deposits of wave-dominated shelf environments. The muddy shelf deposits yield abundant molluscs showing various modes of occurrence that can be divided into three fossil assemblages : (1) the autochthonous Modiolus maedae-Tetorimya carinata assemblage with commonly in-situ preserved semi-infauna and deep burrowers; (2) the Entolium inequivalve assemblage characterized by mixed autochthonous infauna and parautochthonous free-living elements; and (3) the allochthonous Inoceramus maedae assemblage. The Entolium inequivalve assemblage contains the chemosymbiotic bivalve Solemya and is associated with a low-diversity ichnofauna suggestive of low oxygen conditions.
