The taxonomy, distribution, and evolution of the Upper Cretaceous echinoid Micraster

Abstract

On the basis of spatangoid echinoids the Cretaceous seas of the American, European and North African continents are divided into two Faunal Realms - the North African and the European Realm. Contemporary allopatric species of the genus micraster enable distinct Faunal Provinces to be established within the European Realm. These Provinces are called: Northern Faunal Province, Anglo - Paris Basin Province, Touraine - Aquitaine Province and Pyrenean Province. The Provinces are interpreted as reflecting Cretaceous water masses. They are shown to extend further southward with time, particularly during the Coniacian and Campanian periods. Sympatric species of the genus micraster restricted to any Province, are demonstrated to be most easily distinguished by the relative height of their periprocts. The present system of classifying spatangoid echinoids, based essentially on the presence or absence of various fascioles, is rejected. Systematic descriptions are given of most of the species of the genera Micraster and Diplodetus and some species of Epiaster. Two new species (Micraster westlakoi and M. soligmaci) and one new variety (M. corangulnum Var. simpsoni) are established. On the basis of the genus Micraster an attempt is made to correlate the Turonian and Senonian strata of the different European Provinces.