Schroedericonus n. gen. (type-species Dictyoconus turriculus Hottinger and Drobne, 1980), Paleocene larger benthic foraminifera (Orbitolinidae)

Abstract

Abundant specimens of the orbitolinid Dictyoconus turriculus Hottinger and Drobne from Thanetian shallow-water carbonates of the Zagros Zone, SW Iran, allow new taxonomic insights. With a high conico-cylindrical test, lacking a prominent eccentric initial spire and the occurrence of a distinct zone of only primary beams between the marginal zone (with subepidermal network) and central zone, this species always stood out from a morphological perspective among the other species of the genus Dictyoconus Blanckenhorn. However, its generic status was never challenged. The aligned arrangement of the main radial partitions and also of the pillars to a large extent, rules out a possible inclusion of this species in a rigorous classification framework within the genus Dictyoconus Blanckenhorn and therefore, the subfamily Dictyoconinae Moullade because its members display an alternating pattern of the respective structural elements. In addition, intercalary elements also occur and account for the partly irregular pattern, a pattern similar with that of Dictyorbitolina Cherchi and Schroeder. The new genus Schroedericonus is introduced with the new combination Schroedericonus turriculus (Hottinger and Drobne) and assigned to the Dictyorbitolininae Schroeder. As a consequence of this taxonomic review, there are no other species of Dictyoconus in the Paleocene. The distributional pattern of Dictyoconus (upper Cretaceous and Eocene) can be considered as a classical example of iterative evolution.