Cyrtocerinidae is a family of
nautiloid cephalopods
A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, an ...
in the Order
Cyrtocerinida
Cyrtocerinida is an order of Ordovician nautiloid cephalopods. The order includes the families Cyrtocerinidae and Eothinoceratidae, as well as the genera '' Bathmoceras'' and '' Rummoceras''.
Cyrtocerinids can be characterized by a broad si ...
,
previously considered
ellesmerocerids.
Members of the family have slightly endogastric (inwardly curved) breviconic shells with ventral siphuncles that have connecting rings thickened as lobes that project straight into the interior.
Cyrtocerinidae was established by Flower 1964
for the genus ''
Cyrtocerina'' Billings 1865, found at various locations across North America. The shells are generally small, laterally compressed, and dorsum more narrowly rounded than the venter.
References
Prehistoric nautiloid families
Ordovician first appearances
Ordovician extinctions
Ellesmerocerida
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