6533b854fe1ef96bd12ae20f

RESEARCH PRODUCT

The youngest Trigoniida (Mollusca, Bivalvia) of Europe, including new genera and species from the type area of the Maastrichtian Stage

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description

Until recently, only a single species of trigoniid bivalve was known from the upper Maastrichtian Maastricht Formation in the type area of the Maastrichtian Stage (south-east Netherlands and adjacent Belgian and German territories); it was named Trigonia maestrichtiana by Alphonse Briart in 1888. This common, rather small species is here transferred to the genus Oistotrigonia, and a lectotype is designated. In addition, two new genera of very small rutitrigoniids, Wolfgangella and Anniedhondtella, and three new species, W. neilpearti, W. ignota and A. rieui, are erected. Most of the material available is preserved as (paired) external and internal moulds in a nearshore facies of indurated biocalcarenites, but of one species, W. ignota, also silicified shells are available. Oistotrigonia maestrichtiana is the sole species to straddle the Cretaceous–Paleogene (K/Pg) boundary in the area and constitutes the youngest member of the genus known to date. Members of the two new rutitrigoniid genera are confined to the upper Maastricht Formation (Emael, Nekum and Meerssen members). The affiliation of the present trigoniid faunule with assemblages from the upper Maastrichtian of southern India may be due to the preservation of shoreline facies of the same age at both localities, and generally more widespread Late Cretaceous environments due to high sea levels and the spread of warm and shallow epeiric seas.