New species of larger benthic foraminifera from the Maastrichtian deposits of the southern margin of the Neotethys (Zagros Foreland Basin)

Abstract

The investigation mainly focuses on larger benthic foraminifera, Canalispina, Siderolites, Loftusia, and Omphalocyclus from the Maastrichtian deposits (Tarbur Formation) in the Zagros Foreland Basin. The four new species: Canalispina zagrosia sp. nov., Siderolites persica sp. nov., Loftusia tarburica sp. nov., and Omphalocyclus tarburensis sp. nov., and four other index species: Siderolites calcitrapoides, Omphalocyclus cideensis, O. macroporus, and Loftusia baykali were identified. L. harrisoni is thought to be ancestor of L. minor, L. arabica, L. matsumarui, L. tarburica sp. nov., L. occidentalis, L. coxi, L. baykali, L. kahtaensis and L. oktayi during the early, middle and late Maastrichtian, while L. persica and L. elongata evolved into L. arabica in the middle Maastrichtian. L. turcica and L. morgani are close forms of L. elongata in the middle and late Maastrichtian, and L. anatolica and L. morgani are the predominant forms in the late Maastrichtian. The wall structures of Loftusia species are more complex in the late Maastrichtian than in early Maastrichtian forms due to evolutionary trends. Loftusia species with numerous whorls were predominant in the middle Maastrichtian. In contrast to this, the species with low whorl numbers during the early and late Maastrichtian were dominant. Detailed studies on Omphalocyclus species indicate that (1) the genus Omphalocyclus migrated from the middle part of the Tethys to other Tethyan areas during the late Campanian, and (2) the diversity of Omphalocyclus species of eastern Tethys (North African part) was higher than in other areas.