Hanschaubiana, n. gen., from the Eocene of Egypt, with evidence of supplementary life cycles in Foraminifera

Abstract

Hanschaubiana new genus with the type species Assilina nili De La Harpe 1883 is described and photographed and its systematic position revised. The species was established byDe LaHarpe in 1883 and assigned to the genus Assilina from an outcrop of the Early Eocene Thebes Formation at Gebel Deir, near Esna in the Nile Valley. The form belongs to the family Nummulitidae, but it is neither an Assilina nor an Operculina, because it possesses transverse trabecules and does not have alar prolongations. The population consists of 3 morphic forms: agamonts (B Form) and gamonts (AForm), the A-form includes two subgroups:A1 generation, which represents smallmegalospheric tests, andA2 generation, whose test sizes are comparable with the juvenile B-form but with large proloculus and they are also megalospheric tests. Such variation in the A-form is evidence for a three-phase life cycle (trimorphism) that includes: agamonts (B- trimorphic form), gamonts (A1 trimorphic Form), and gamonts (A2 trimorphic Form).Adifferential diagnosis between the new taxon and allied taxa is provided. The new taxon is found associated with Nummulites subramondi De La Harpe 1883, (also topotype) in its type locality.