Craniopsidae is an extinct family of craniiform brachiopods which lived from the

Lower Cambrian The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ago (m ...

(

Botomian Cambrian Stage 4 is the still unnamed fourth stage of the Cambrian and the upper stage of Cambrian Series 2. It follows Cambrian Stage 3 and lies below the Wuliuan. The lower boundary has not been formally defined by the International Commission on ...

) to the

Lower Carboniferous Lower may refer to: *Lower (surname) *Lower Township, New Jersey *Lower Receiver (firearms) *Lower Wick Lower Wick is a small hamlet located in the county of Gloucestershire, England. It is situated about five miles south west of Dursley, eight ...

(

Tournaisian The Tournaisian is in the ICS geologic timescale the lowest stage or oldest age of the Mississippian, the oldest subsystem of the Carboniferous. The Tournaisian age lasted from Ma to Ma. It is preceded by the Famennian (the uppermost stage ...

). It is the only family in the

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

superfamily Craniopsoidea and the monotypic order Craniopsida. 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.

References

External links

* *
Craniopsodae at fossiilid.info
Craniopsida Prehistoric protostome families Brachiopod families Cambrian first appearances Carboniferous extinctions {{Brachiopod-stub