Dercetid fishes from the Maastrichtian type area (Upper Cretaceous) of Belgium and the Netherlands

The family Dercetidae comprises a diverse array of marine aulopiform actinopterygians. Until now, merely seven specimens, assigned to five species, were recorded from the Maastrichtian type area. Here, around two dozen dercetid fossils, originating from a number of quarries and outcrops in north-eastern Belgium and the south-eastern Netherlands are described and illustrated. This material comprises two new genera, Beukidercetis gen. nov. and Petrodercetis gen. nov., and four new species: Caudadercetis taverni sp. nov., Beukidercetis lissus gen. et sp. nov., Cyranichthys sideralis sp. nov., and Petrodercetis bidirectus gen. et sp. nov. Newly collected specimens of Cyranichthys jagti, Dercetis triqueter and Ophidercetis italiensis are also added, because these extend their respective stratigraphical ranges in the study area. Moreover, material here assigned to Dercetoides venator and a specimen resembling Cyranichthys ornatissimus markedly expand their geographical and stratigraphical ranges. In general, the present material reflects an underappreciated diversity of dercetids in the Maastrichtian type area, even though that they fossilize well compared to other late Maastrichtian actinopterygians from the study area. This high degree of preservation may be related to a benthic lifestyle, or to their slender, scute-covered bodies that may have been less vulnerable to disruption than those of other actinopterygians.