Abstract
A well-preserved fossil bivalve is here described as a new species, Halicardia toyamaensis sp. nov., collected from a calcareous nodule within gray mudstone of the latest Early to earliest Middle Miocene Kurosedani Formation at Kashio, Yatsuo-machi, Toyama City, central Japan. The genus Halicardia is represented today by twelve living species that inhabit the upper bathyal to abyssal zones. In the Kurosedani Formation, most molluscan fossils occur as scattered articulated and disarticulated shells within mudstone; this taphonomic mode indicates a para-autochthonous assemblage. Considering the habitat depths of the associated molluscan fossils and the depositional environment inferred from benthic foraminiferal fossils, the depositional depth of the Kurosedani Formation at the study site is estimated to have been within the upper bathyal zone.
https://ror.org/0163dw893 
