The early evolution and palaeobiogeography of Mesozoic planktonic foraminifera

Abstract

The planktonic foraminifera almost certainly evolved from benthonic ancestors in the early Jurassic. The meroplanktonic genus Conoglobigerina, known from south-central and eastern Europe, appears in the Bajocian and is probably derived from the even more geographically restricted Praegubkinella. This genus was represented by a single taxon in the earliest Toarcian but diversified after the Toarcian anoxic event. At the same level Oberhauserella quadrilobata Fuchs, 1967 became more inflated and there is some evidence to suggest that the ‘anoxic event’ was the environmental perturbation that began the transition to a planktonic mode of life. In the Callovian-Oxfordian interval, the planktonic foraminifera are still restricted to a relatively limited area bounded by the North Atlantic Ocean, NW Europe and Eastern Europe and this remained the case even in the earliest Cretaceous. It was only in the Aptian-Albian that the palaeogeographical distribution changed dramatically, probably as a response to the elevated sea levels caused by the increased rate of ocean crust production which began in the Early Aptian. The principal diversification events in the Jurassic (Toarcian, Bajocian, Callovian-Oxfordian) also appear to be related to sea level highstands.

European ammonoid diversity questions the spreading of anoxia as primary cause for the Cenomanian/Turonian (Late Cretaceous) mass extinction

“…It is essential to note that studies of the global diversity of Cretaceous planktonic foraminifers (e.g. Hart 1999;Premoli Silva & Sliter 1999;Hart et al 2002) have shown that anoxic events cannot be described as 'controlling factor' of the evolution of planktonic foraminifers. These studies emphasize that OAE2 is not associated with a drop in foraminifer diversity, but with a major turnover and a slight increase in taxonomic richness.…”

Palaeobiogeography and the Ordovician and Mesozoic-Cenozoic biotic radiations

“…tropical/subtropical) facies in the Early Jurassic (Toarcian) (Hart et al 2002). A biostratigraphic analysis has indicated some expansion within the North Atlantic-European region in both the Bajoican-Bathonian and Aptian, but it was not until the latest Albian that a near-global distribution was achieved.…”

Global bioevents and the Cretaceous/Paleogene boundary in Texas and Alabama: Stratigraphy, correlation and ocean acidification

“…This is almost the same time that the planktic foraminifers appeared in the Tethys Ocean (Wernli, 1995;Wernli and Görög, 1999;Hart et al, 2003Hart et al, , 2012aHudson et al, 2009). The planktic foraminifers did not, however, become diverse and abundant until the Early Cretaceous (Premoli Silva and Sliter, 1999;Hart, 1999;Hart et al, 2002). All of the Jurassic planktic foraminifers appear to have been relatively simple 'globigerine' forms with aragonitic tests (Hart et al, 2012a).…”