Middle Jurassic bryozoans from the Carmel Formation of southwestern Utah

Abstract

Very few Jurassic bryozoan faunas are known outside Europe. Here we describe seven species of calcareous cyclostome bryozoans and one bioimmured soft-bodied ctenostome bryozoan (Simplicidiumsp.) from the Middle Jurassic (?Bathonian) Carmel Formation of Utah. Three of the cyclostomes are placed in open nomenclature due to inadequate preservation and/or the lack of key reproductive polymorphs. A new genus,Patulopora,is established forDiastopora cutleriCuffey and Ehleiter, 1984, following the discovery of gonozooids that place this species in the Multisparsidae rather than in the Plagioeciidae. Another of Cuffey and Ehleiter's (1984) species—Berenicea duofluvina—is reassigned toMicroeciellaon the basis of the gonozooids, and a similar but distinctly smaller form is described asM. pollostosnew species. A second new species—Hyporosopora nielsoni—is a rare colonist of hardground undersurfaces. The Carmel bryozoan fauna is compared with better-known faunas from the northern European Middle Jurassic. Species richness and colony-form diversity fall well within the expected values for bryozoan faunas of this age, and endemism is detectable only at relatively low taxonomic levels. Evolutionary patterns based on studies of contemperaneous European bryozoan faunas during this time of cyclostome evolutionary radiation are reinforced by the palaeogeographically distant Carmel bryozoan fauna.