Carboniferous arachnids from the Graissessac Basin, Central Massif, France

Abstract : Trigonotarbids and scorpions (Arachnida: Trigonotarbida, Scorpiones) are described from the Upper Carboniferous (Late Stephanian/Late Gzehlian) of the Graissessac Basin in the Central Massif outcropping in southern France. This is the first record of trigonotarbids and the first thorough description of scorpions from this locality. Trigonotarbids are an extinct order and the new fossils express a distinctly ornamented dorsal surface and lobed carapaces implicit of the so-called ‘eophrynid-assemblage’; probably a derived clade. Although closest to Eophrynidae, the character combination preserved precludes unequivocal assignment to any of the currently recognized families, but appears to be unique among trigonotarbids and prompts us to propose the name Aenigmatarbus rasteli gen. et sp. nov. to accommodate these novel specimens. The Graissessac scorpions are preserved in dorsal view only, but two distinct morphotypes could be recognized. These are tentatively referred to here as two typical Coal Measures genera: namely the mesoscorpion Eoscorpius sp. and the more derived orthostern Compsoscorpius sp., respectively.