Multiple Orbitoides d’Orbigny lineages in the Maastrichtian? Data from the Central Sakarya Basin (Turkey) and Arabian Platform successions (Southeastern Turkey and Oman)

Abstract The standard reconstruction of species Orbitoides d’Orbigny into a single lineage during the late Santonian to end Maastrichtian is based upon morphometric data from Western Europe. An irreversible increase in size embryonic apparatus, and formation greater number epi-embryonic chamberlets (EPC) with time, regarded as main evolutionary trends used discrimination. However, assemblages Central Turkey Arabian Platform margin (Southeastern Oman) are not consistent this record. Besni Formation Southeastern yields invariably biconvex specimens, small, tri- quadrilocular embryons small EPC, comparable Campanian medius (d’Archiac). upper Tarakl? Sakarya Basin contains two distinct, yet closely associated forms Orbitoides, easily differentiated by both external internal features. Flat biconcave specimens possess apparatus -type whereas large, predominantly bilocular were assigned ex. interc. gruenbachensis Papp– apiculatus Schlumberger on morphometry. flat belong long overlooked pamiri Meriç, originally described Tauride Mountains SW Turkey. This herein interpreted be an offshoot Maastrichtian, that we term ‘ ’, since they recall species, younger than normal occurrence accepted morphometrically defined lineage. correlation between test features O. implies shape ecophenotypic variation, but appears biologically controlled. We, therefore, postulate more one exists includes O . ’ displaying retrograde