Early Cretaceous brachiopods from a hydrothermally influenced environment of the Mecsek Mountains (Zengővárkony, southern Hungary) and their palaeobiogeographical relationships

Abstract

New material and the investigation of old collections provided some 150 specimens of Early Cretaceous brachiopods from the Mecsek Mountains, Hungary. Taxonomic evaluation resulted in the identification of some species previously unknown from Hungary and confirmed the presence of some previously described species, too. In this paper Fortunella cf. fortunae Calzada, 1985, Lacunosella hoheneggeri (Suess, 1858), Monticlarella remesi Nekvasilova, 1977, Moutonithyris moutoniana (d’Orbigny, 1847), Karadagella ? aff. bilimeki (Suess, 1858), Nucleata veronica Nekvasilova, 1980 are described. This fauna is rather endemic. All the specimens reveal a unique phenomenon: they exhibit 25–70% larger average dimensions compared to populations of their closest relatives or type localities. The uniform size increase of these brachiopods may be linked to hydrothermal processes of the sea-floor. Lately, a discovery from the Tyrrhenian Sea offers a Recent, present day analogue to this enigmatic palaeoenvironment. Palaeobiogeographic comparison of this small endemic fauna with eight others, mainly Hauterivian and Tethyan brachiopod assemblages reveals the distinct Sub-Tethyan domain consisting of the faunas from Zengővárkony, Codlea (Eastern Carpathians) and Štramberk (Czechia). This strengthens previously described affinities and relationships of these faunas and helps to clarify the Cretaceous palaeogeographic position of the Mecsek Mountains.