Craniopsidae

Craniopsidae is an extinct family of craniiform brachiopods which lived from the Lower Cambrian (Botomian) to the Lower Carboniferous (Tournaisian). It is the only family in the monotypic superfamily Craniopsoidea and the monotypic order Craniopsida.[1]

Craniopsidae Temporal range:
Scientific classification
Kingdom:	Animalia
Phylum:	Brachiopoda
Class:	Craniata
Order:	†Craniopsida Gorjansky & Popov, 1985
Family:	†Craniopsidae Williams, 1963
Genera
†Craniops Hall, 1859 †Discinopsis Hall & Clarke 1892 †Lingulapholis Schuchert 1913 †Paracraniops Williams 1963 †Pseudopholidops Bekker, 1921 †Wrightiops Popov and Cocks 2014
Synonyms
Sanxiaella

Craniopsids were among the earliest and simplest brachiopods to appear. The calcitic shell was rounded in profile and biconvex, with both valves equally convex. Like other craniiforms, they had two pairs of adductor (vertical closing) muscles and two pairs of oblique (diagonal sliding) muscles, with the muscle scars shifted to near the center of the shell. They show some similarities with kirengellids, a group of problematic Cambrian fossil shells of marine organisms.[1]