New Middle Miocene Argyrotheca (Brachiopoda; Megathyrididae) species from the Central Paratethys

Abstract

The shallow water micromorphic brachiopod assemblages of the Central Paratethys are generally dominated by
members of the family Megathyrididae (Megathiris, Argyrotheca, Joania). Several localities are recorded in the literature
which are characterized by the dominance of Argyrotheca (and also of Joania, which has recently been differentiated
from Argyrotheca). In earlier papers published in Central Europe, several names were used for these forms. However,
after careful revisions over recent decades, only two species have been confirmed in the Badenian (Middle Miocene) of
the Central Paratethys: A. cuneata and A. cordata; the latter is now regarded as the type-species of the recently recognised
Joania.
Some samples collected in 2006 from the Lower Badenian Heterostegina Sand on the southern slopes of the Holy
Cross Mts (near Szydłów, Poland) yielded an abundant and new Argyrotheca species (together with some Joania cordata,
Megathiris detruncata, Platidia anomioides and Discinisca sp.). Later, some specimens of the same form were found in
the Middle Miocene Central Paratethyan samples of the Netherlands Centre for Biodiversity (NCB) Naturalis in Leiden
(the Netherlands). This form had already been illustrated in earlier papers by some Polish authors. However, it was
erroneously confused with the Recent Mediterranean Argyrotheca cistellula. In this paper Argyrotheca bitnerae n. sp. is
described on the basis of the newly collected Szydłów assemblage, the limited material of the NCB Naturalis, as well as
the revision of some larger collections in the Muzeum Ziemi (Warsaw), which were described by the late Ewa POPIELBARCZYK. According to the known data, palaeogeographic distribution of Argyrotheca bitnerae n. sp. is limited to the
northern part of the Central Paratethys.