Bakhtiarellidae, a new end-Cretaceous ‘hauraniiform’ family of Larger Benthic Foraminifera: taxonomic inventory and phylogenetic assessment

Abstract

ABSTRACT Bakhtiariella, a new genus of Larger Benthic Foraminifera is described from the upper Maastrichtian Tarbur Formation of Iran. The new taxon is characterised by a trochospirally coiled initial test part with angular chamber margins, later uncoiling and becoming rectilinear and presenting a coarse subepidermal network of horizontal and vertical partitions. Appearing as an extension of the subepidermal alveolar layer (exoskeleton), the pseudotriangular-shaped main partitions extend inwards and stretch downwards to the chamber floor where their arrangement is related to the inner margin of the central area with irregularly distributed pore-like foramina. Together with Persiacyclammina, which also displays such peculiar ‘subepidermal septula’, Bakhtiariella is included into the new family Bakhtiarellidae, and further compared with the Jurassic–Lower Cretaceous Hauraniidae. The new family gives further evidence for the diversification and pronounced endemism (Arabian Plate) of Larger Benthic Foraminifera within the final phase of the so-called Upper Cretaceous Global Community Maturation Cycle. This leads to the conclusion that both Persiacyclammina and Bakhtiariella can be considered ‘Key Mesozoic Benthic Foraminifera of the Middle East’.