Family
Heteroporidae
Heteropora pacifica. Photo: (c) Alex Bairstow, some rights reserved (CC BY-NC)
Cyclostomatida, or cyclostomes (which also refers to a group of jawless fish called Cyclostomata), are an ancient order of stenolaemate bryozoans which first appeared in the Lower Ordovician. It consists of 7+ suborders, 59+ families, 373+ genera, and 666+ species. The cyclostome bryozoans were dominant in the Mesozoic; since that era, they have decreased. Currently, cyclostomes seldom constitute more than 20% of the species recorded in regional bryozoan faunas.