Angustidontid crustaceans from the Late Devonian of Strud (Namur Province, Belgium): insights into the origin of Decapoda

International audienceThe new angustidontid crustacean Schramidontus labasensis gen. et sp. nov. is described from the floodplain and temporary pond deposits from the Famennian (Late Devonian) of Strud, Belgium, together with a rare Palaeozoic assemblage of crustaceans (decapods, conchostracans, notostracans and anostracans) and eurypterids. This material documents the first occurrence of angustidontids in continental environment whereas it was previously only known from marine (pelagic) environments and enlarges the geographical distribution of angustidontids from North America and Eastern Europe to Western Europe. Schramidontus labasensis gen. et sp. nov. substantially differs from Angustidontus seriatus Cooper, 1936 by having the first two pairs of thoracopods modified as maxillipeds (grasping appendages). Since both taxa indubitably belong to Eucarida but differ from Amphionidacea, Decapoda and Euphausiacea, we erect the new order Angustidontida for these Devonian fossils. We postulate that Angustidontida order nov. fills the gap between Amphionidacea (characterized by a unique pair of thoracopods modified into maxillipeds) and Decapoda sensu stricto (three maxillipeds). This suggests that early decapods may had autapomorphically at least one pair of maxillipeds and further changed in Decapoda s. str