New observations on Upper Devonian brachiopods from the Namur-Dinant Basin (Belgium)

Brachiopods (Productida [except Chonetidina], Orthida, Athyridida, Spiriferida [Adolfiidae, Reticulariidae, Ambocoeliidae, Thomasariidae], and Spiriferinida) recovered in the interval, in terms of the standard conodont zonation, between the Palmatolepis hassi and P. triangularis zones (Late Middle Frasnian to Early Famennian) in the Namur-Dinant Basin (Belgium) are described. The orders and suborders investigated include 32 species: 21 are described in open nomenclature, seven are previously known, four are new of which three are assigned to previously known genera: Aulacella aggeris n. sp., Dicamara plutonis n. sp., and Warrenella (Warrenella) aquaealbae n. sp. The fourth species belonging to a newly defined genus: Neptunathyris buxi n. gen., n. sp. A major brachiopod faunal change occurs at the top of the P. rhenana Zone in southern Belgium, with the disappearance of most existing species in parallel with the deterioration of the oxygenation conditions preceding the Upper Kelwasser Event. Only an impoverished fauna (Lingulida, Chonetidina, Rhynchonellida) has been collected in the P. linguiformis Zone. The recovery of the Famennian brachiopods after the end-Frasnian biotic crisis was rapid in the basal Famennian but, despite their great abundance, their diversity was relatively low. New cosmopolitan genera appeared at this time especially among the rhynchonellids, athyridids and spiriferids with new species of pre-existing orthid and orthotetid genera.