Biogeography and species durations of selected cenozoic shallow and deep-water smaller calcareous benthic foraminifera- a review

Most previous accounts summarising the biogeography and species durations of smaller calcareous benthic foraminifera have been based on literature reviews or on a massive North American database that had been taxonomically standard-ised. In this review we limit consideration to extant and fos-sil families or genera (from nearshore, open shelf, and deep-sea environments) with modern reviews that have standardised their global morphotaxonomy and where available, are com-plimented by molecular studies.We confirm previous studies that indicate most shelf species have limited geographic ranges and the majority of deep-water species are widespread and cosmopolitan or nearly so. In our intertidal and inner shelf groups only one species (molecu-lar and morphological), Ammonia veneta, has a cosmopoli-tan distribution, although four warm-water morphospecies, of Ammonia and Rugobolivinella, have or had distributions that spanned more than one ocean in equatorial latitudes. The ma-jority of both warm-and cool-water species in these groups are regionally or locally-restricted endemics (92% of Bo-livinellidae, 100% of Tubulogenerina, 73% of Ammoniidae). The biogeographic distribution of the two rarer, warm-water groups (Bolivinellidae, Tubulogenerina) changed dramatically through the Cenozoic with the Paleocene-Eocene North American-European distribution of Bolivinellidae switching to purely Indo-Pacific by the Pliocene-Quaternary.In our shelf-upper bathyal groups (Notorotaliiidae, Plectofrondiculariidae), two genera have been restricted to the Southern Hemisphere since their Eocene originations with their greatest diversity throughout in New Zealand and Australia, respectively. The dominantly cold-water no-torotaliid genus Buccella has a biogeographic distribution largely restricted to the Arctic Ocean and both coasts of North and South America. Most notorotaliid species are locally or regionally endemic (100% of Notorotalia, Par-rellina, Porosorotalia, 75% of Buccella). At least 50-60% of species in five extinct mid-bathyal-abyssal families are cosmopolitan and have been throughout the Cenozoic since their originations. The majority of these deep-sea species with more-restricted distributions are rare, and many could possibly be more widespread with further extensive study.This review found that the shortest mean species dura-tions (4-5 myrs) occur in two groups of rather rare, tropical -subtropical inner-shelf foraminifera with many locally endemic species. In cooler and progressively deeper water environments the mean species durations increase to 7-11 myrs for tem-perate shelf-bathyal taxa (Notorotaliidae), 20 myrs for an extinct mid-shelf to bathyal family (Plectofrondiculariidae) and 41-50 myrs for five extinct mid-bathyal-abyssal fam-ilies (Chrysalogoniidae, Ellipsoidinidae, Glandulonodosari-idae, Pleurostomellidae, Stilostomellidae). One species in each of four of these deep-water families had a species dura-tion of 150-120 myrs.