Gigantoproductid and allied productid brachiopods from the “Calcaires à Productus” (late Viséan-Serpukhovian; Montagne Noire, southern France): Taxonomy and palaeobiogeographical position in the Palaeotethys

Abstract

The “Calcaires à Productus” or “Calcaires à Productus giganteus” on the southern slope of the Montagne Noire (Hérault, France) consist of numerous isolated olistolitic limestone blocks, generally transported by gravitational flows into siliciclastic basinal deposits. The present paper is the first systematic monographic study of gigantoproductids, semiplanids, and some other large-sized productid brachiopods from the upper Viséan to Serpukhovian strata of the Montagne Noire. Gigantoproductids are represented by abundant Datangiasemiglobosa and Kansuella spp.; a single Globosoproductus specimen is described. The semiplanids are represented by Latiproductus aff. latissimus, L. latissimus complicatus and L. edelburgensis, and the linoproductids by Balakhonia aff. kokdscharensis. The Montagne Noire productid faunas are found in very different facies including shell beds and microbial mounds. They are most abundant in assemblages from agitated, shallow water environments with a firm substrate where rugose corals are rare or absent. The palaeobiogeographical relations to the other regions in the western Palaeotethys are often limited to taxa with an almost cosmopolitan character. Worth noting is the absence of Gigantoproductussensu stricto in the Montagne Noire. This genus, and other brachiopod taxa, migrated probably during the late Serpukhovian into southern France. On a larger scale, the presence of Kansuella indicates faunal exchanges with the eastern Palaeotethys (South China) via a westward migration path along North China, the Central Asian Orogenic Belt and south-eastern Laurussia. The studied taxa, even at the genus level, did not migrate into North America even if the Alleghanian Isthmus was still open.