MIDDLE DEVONIAN BRACHIOPODS FROM THE SOUTHERN MA?DER (EASTERN ANTI-ATLAS, MOROCCO)

摘要

Sixty-two Middle Devonian brachiopod species are described on the basis of 1300 specimens from the Taboumakhlo?f Formation (and subordinately probably also from the top of the El Otfal Formation) at Mad?ne el Mrakib (middle to late Eifelian or early Givetian?), Aferdou el Mrakib (late Eifelian to middle Givetian), and Guelb el Maharch (early Givetian) on the southern edge of the Ma?der Syncline (eastern Anti-Atlas, Mo- rocco). Representatives of Craniida (2 taxa), Strophomenida (5), Productida (2), Orthotetida (2), Orthida (5), Pentamerida (5), Rhynchonellida (9), Atrypida (14), Athyridida (7), Spiriferida (9), and Spiriferinida (2) are present. The fauna is dominated quantitatively by the Atrypida (24% of taxa, about the half of specimens, and the commonest species Atryparia dispersa making up about 13% of the material); the Rhynchonellida (16% of taxa, about one-sixth of specimens) are the second largest order. A new genus of the family Pugnacidae (order Rhynchonellida), Paulinaerhynchia, is proposed with the type species P. paulinae gen. et sp. nov. from Maharch; it is closest to Pugnax, from which it differs in distinct costation, lack of a dorsal septum and septalium, and rudimentary dental plates. Desquamatia (D.) deserti sp. nov., a large and finely costate representative of the genus, is described also from Maharch. Antirhynchonella and Glosshypothyridina are reported for the first time or con- firmed to be present in the Givetian. Forty (possibly up to 46) species (71 or possibly up to 82% of the taxa identified at the species level) are present also in either Eifel (Germany) or the Holy Cross Mountains (Poland). Such a high ratio of species in common attests to unconstrained faunal exchanges among benthic faunas between the northern and southern shores of the Variscan Sea during the Middle Devonian. This favours the palaeogeo- graphic hypothesis of a narrow Variscan Sea.