Provinciality of the Mediterranean lower Jurassic brachiopod fauna: Causes and plate-tectonic implications

The composition of 23 “NW European” and “Mediterranean” Lower Jurassic (Pliensbachian) brachiopod faunas is compared at the species level. On the basis of this quantitative approach, the two “provinces” can be delimited more sharply than by earlier qualitative studies. In the author's opinion the most reasonable cause of the provinciality is as follows: in the Middle Triassic a segment of the European shelf became rifted, detached and drifted toward the open Tethys ocean. Being isolated, the brachiopods of this province could produce evolutionary lineages different from the European ones. If the presence of this contiguous and separate Triassic—Jurassic microcontinent characterized by Mediterranean brachiopod faunas is assumed, this factor should be borne in mind in the reconstructions concerning the closure of the Tethys (= Alpine orogeny).