Non-marine Bivalvia of the mid-Cretaceous Kem Kem Group of southeastern Morocco

Invertebrate fossils are rare in the famously vertebrate-rich mid-Cretaceous Kem Kem Group of southeastern Morocco. This study presents the first detailed account of freshwater bivalves from this important stratigraphic unit. The fossils described originate from the Ifezouane Formation, the lower sandy unit of the group. The superfamily Trigonioidoidea is represented by Monginella cf. flattersensis , the new genus Goumardonaia introduced for ? Monginella radieri and the new genus and species Kemkemnaia parvum (Desertellidae). Specimens referred to the Unionidae include the new species Unio radleyi , which with Kemkemnaia parvum are potentially endemics. This study reveals a previously unrecognised freshwater bivalve diversity in the mid-Cretaceous deposits of North Africa. Most of the bivalve specimens are fragmentary, reflecting the dynamic fluvial environment of the Kem Kem Group, and are preserved as ferruginous sandstone internal moulds. • A highly freshwater diverse bivalve assemblage of at least 5 genera is described from the Kem Kem Group of Morocco. • Two new potentially endemic bivalve taxa are erected. • Implications for palaeoenvironment and palaeoecology of the important mid-Cretaceous deposit.