On the Pleurotrigoniinae VAN HOEPEN, 1929 (Trigoniida: Trigoniidae); their evolution and classification

摘要

The subfamily Pleurotrigoniinae has long been treated a synonym of the Trigoniinae. Here two new genera and two new species of pleurotrigoniine bivalve are described from the Cretaceous of South Africa and Australia, providing the evolutionary link between Aptian Sphenotrigonia and Cenomanian Pleurotrigonia, the type species of which are re-described. These new taxa establish the subfamily Pleurotrigoniinae as an important Gondwanic lineage, ranging in age from Barremian to Maastrichtian. The early growth stages of Sphenotrigonia point unequivocally to an origin in Nototrigonia, and here the subfamily Nototrigoniinae is reduced to a tribe within Pleurotrigoniinae. The new tribe Kupengini is separated from Nototrigoniini and assigned to Neotrigoniinae, of which it is regarded the progenitor.