石燕贝目

一类早已灭绝的海生 无脊椎动物. 石燕贝类化石属 腕足动物门具铰纲.壳为双凸型，偶见平凸型.铰合线直长，铰合面发育或不发育，三角孔洞开或部分为三角双板覆盖，可具有基孔.牙板发育.绝大多数具腕螺，螺顶指向两主端，有时腕螺之间有腕锁相连.壳具疹或无疹，壳面具壳线、壳褶或光滑无饰.中 奥陶世开始出现，至 侏罗纪灭绝.A class of long-extinct marine invertebrates. Sekien brachiopod shellfish fossils belong to a door hinge Class. Shell for the double-convex type, occasionally flat convex. Hinge line straight long hinge surface development or not development, Triangle holes open or in part, for the triangular double-plate cover, may have the base hole. dental lamina development. the vast majority of a wrist-Lo, Lo Top two primary end point, and sometimes the wrist between the wrist lock screw connected. shell with measles or no rash, shell mask shell line, the shell-fold, or smooth without ornaments. began to appear in the Ordovician to Jurassic extinction.