Craniopsidae is an extinct family of
craniiform brachiopods
Brachiopods (), phylum Brachiopoda, are a phylum of animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the fron ...
which lived from the mid-
Cambrian
The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...
to the
Lower Carboniferous (
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 st ...
). 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 "unisp ...
superfamily Craniopsoidea and the monotypic order Craniopsida.
If one includes the ambiguous Cambrian genus ''
Discinopsis'', craniopsids were the first craniiforms to appear, and may be ancestral to
craniids and
trimerellides.''
'' An even earlier Cambrian genus, ''
Heliomedusa'', has sometimes been identified as a craniopsid. More recently, ''Heliomedusa'' has been considered a
stem-group
In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...
brachiopod related to ''
Mickwitzia''.
Craniopsids are among the simplest of brachiopods, with few identifiable features shared between genera. The
calcitic shell is 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 just behind the center of the shell. They show some similarities with
kirengellids, a group of problematic Cambrian fossils representing the shells of marine organisms.
List of genera
* †''
Craniops''
Hall, 1859 Caradoc
Caradoc Vreichvras (; Modern , ) was a semi-legendary ancestor to the kings of Gwent. He may have lived during the 5th or 6th century. He is remembered in the Matter of Britain as a Knight of the Round Table, under the names King Carados and C ...
") – Lower Carboniferous (late Tournaisian)]
* †''
Discinopsis?''
Hall & Clarke 1892 [mid-Cambrian]
* †''Lingulapholis''
Schuchert 1913 evonian* †''
Paracraniops''
Williams 1963 Llandovery
Llandovery (; ) is a market town and community (Wales), community in Carmarthenshire, Wales. It lies on the River Tywi and at the junction of the A40 road, A40 and A483 road, A483 roads, about north-east of Carmarthen, north of Swansea and w ...
)]
* †''Pseudopholidops''
Bekker, 1921 [Ordovician]
* †''Wrightiops''
Popov and Cocks 2014 [Upper Ordovician (Katian)]
References
External links
*
Craniopsodae at fossiilid.info
Craniopsida
Prehistoric protostome families
Brachiopod families
Cambrian first appearances
Carboniferous extinctions
{{Brachiopod-stub