Distephanopsis concavus Horvat: a revised silicoflagellate species from the Middle Miocene of the Central Paratethys

Abstract

The silicoflagellate species Distephanopsis concavus Horvat is revised based on further research of the type material. This species is characterized by having a basal ring with strongly concave sides which reduce the basal ring area and by four symmetry planes which are morphological characteristics not known in other Distephanopsis species. The species was found in Middle Miocene deposits of the Central Paratethys. Its occurrence at type locality in SE Slovenia is dated to late Middle Badenian and is correlated to the upper part of the nannoplankton biozone NN5.