The foraminifera genus Amphistegina in the Korytnica Clays (Holy Cross Mts, Central Poland) and its significance in the Miocene of the Paratethys

Abstract

Different populations of Amphistegina from the Central Paratethys have been studied and compared with the faunas of the Korytnica Basin, Central Poland. A biometrical computer analysis was used in order to solve the systematical problems of the species concept. The test shape and chamber development of the investigated species, taking in consideration relevant Recent species, demonstrated the phylogenetic relations and the differences between the species in question. Two main groups can be separated immediately. The first includes the species Amphistegina mammilla (FICHTEL & MOLL), A. hauerina D'ORBIGNY, and A. radiata (FICHTEL & MOLL), and is represented in the Miocene by only one species, namely A. mammilla. The Indo-Pacilic origin of this fauna is proved by the close relation with A. radiata. The Amphistegina lessonii D'ORBIGNY- species group is shown to have been represented by an independent species in the European Miocene, by Amphistegina bohdanowiczi BIEDA. It inhabited the Central Paratethys from the early Miocene to the early Badenian. The Miocene forms were generally dextrally coiling. The existence of a subtropical climate during the Middle Miocene in Central Europe is supported. By means of the Amphistegina assemblages a biostratigraphic determination of the Korytnica Clays as early Badenian (corresponding the Lower Lagenidae Zone) was possible.