The last representatives of the order Atrypida on the southern flank of the Dinant Synclinorium (Vaulx-Nismes area) in Belgium belong to Costatrypa, Spinatrypa, Spinatrypina (?Spinatrypina), Spinatrypina (Exatrypa), Iowatrypa, ?Waiotrypa, Desquamatia (Desquamatia) and Desquamatia (?Seratrypa). Among the thirteen described taxa, five are new: Spinatrypa tumuli sp. n., Iowatrypa circuitionis sp. n., ?Waiotrypa pluvia sp. n., Desquamatia (Desquamatia) quieta sp. n. and Desquamatia (?Seratrypa) derelicta sp. n. Supposed lissatrypid `Glassia drevermanni' Maillieux, 1936 from the late Frasnian Matagne shales is assigned to the Rhynchonellida. On the southern flank of the Dinant Synclinorium and in the Philippeville Massif, the Atrypida become extinct in the Palmatolepis rhenana Zone, significantly below the Frasnian-Famennian (F-F) boundary. Their extinction coincides with the first appearance of the green and black shales of the late Frasnian Matagne Formation, recording a transgressive-hypoxic event. Based on conodont data, this event takes place earlier on the southern flank of the Dinant Synclinorium than in the Philippeville Massif.

Key words: Brachiopoda, Atrypida, taxonomy, biostratigraphy, mass extinction, Kellwasser Crisis, Frasnian, Devonian, Belgium.

Jacques Godefroid [jgodefr@d5100.kbinirsnb.be], Institut Royal des Sciences Naturelles de Belgique, Département de Paléontologie, rue Vautier, 29, B-1000 Bruxelles, Belgium.Stefan Helsen, Katholieke Universiteit Leuven, Departement Geologie-Geografie, Afdeling Historische Geologie, Redingenstraat 16, B-3000 Leuven, Belgium.