Originations, radiations and extinctions of Cretaceous rudistid bivalve species in the Caribbean Province

Abstract

Rudistid bivalves first immigrated into the Caribbean Province in the Valanginian. They initially constructed reefoid frameworks in the central Caribbean Tethys by the Aptian, and dominated reefs of the Caribbean Tethys from the Albian through the Maastrichtian. During the Cretaceous, Caribbean rudistids underwent two major radiations, the first beginning in the Middle Albian and peaking in the Late Albian, and the second extending from the Early Santonian to a Middle Maastrichtian peak. These radiations were punctuated and separated by prominent extinction episodes, including the earliest phases of three global mass extinctions. Of the two hundred and fourteen described Caribbean rudistid species, each stratigraphically located to substage or finer levels of resolution, only eleven species (5.1%) are known from elsewhere in the world, suggesting extensive genetic isolation of the Caribbean reef biotas throughout the Cretaceous. This high level of species endemism (95%) allows definition of true regional origination and extinction patterns; these may represent global patterns for the rudistids. Radiation and extinction patterns in the Caribbean Province can be variously related to eustatic sealevel fluctuations, Caribbean plate motions affecting reef platforms, Antillean arc volcanism and drowning of carbonate platforms in volcaniclastic debris, paleoclimate (mainly temperature) oscillations and their effect on the paleobiogeographic distribution of reef biotas, and on the early effects of forcing mechanisms for global mass extinction. The origination and extinction patterns for all Caribbean rudistid species reflect this dynamic regional history. Analyses of species per substage, species per Ma, and species per Ma per diversity yield similar results and represent the most detailed analysis of origination and extinction history among dominant Tropical macrobiotas. Small origination peaks in the Early Barremian and Early Aptian emerge on only per taxon plots, but persistent major origination peaks occur in the Early Turonian, Early Coniacian, Early Santonian, and Early Maastrichtian. Significant extinction peaks among rudistids occur in the Late Aptian, Early Cenomanian, Late Cenomanian, Late Turonian, Middle Coniacian, Late Santonian, and early Late Maastrichtian. The Late Aptian, Late Cenomanian, Late Turonian, Middle Coniacian and Late Maastrichtian extinctions are true extinctions in that they occur during low or zero origination rates among rudistids. The Aptian, Cenomanian, and Maastrichtian rudistid extinctions occur in association with global mass extinctions, but consistently earlier than the main extinction peaks in each case by 0.25 to 1 Ma.