rudist

(paleontology) Any of many box-, tube- or ring-shaped marine heterodont bivalves from the Jurassic and Cretaceous periods.

日本語の意味

ジュラ紀および白亜紀に生息していた、箱形、管形、輪形などの形状を持つ、海洋性の異形二枚貝類（化石生物）

The paleontologist carefully extracted a fossilized rudist from the limestone cliff.

古生物学者は石灰岩の崖から化石化した箱形・管形・環形の海生異歯二枚貝を慎重に取り出した。

意味（1）

(paleontology) Any of many box-, tube- or ring-shaped marine heterodont bivalves from the Jurassic and Cretaceous periods.

In its shallow waters, now-extinct clams known as rudists formed extensive beds.

rudists

（ plural ）