A new basal balanomorph cirripede (Thoracica, Brachylepadidae) from the Upper Cretaceous and its bearing on the evolutionary origins of the group

Abstract

A tiny, sessile brachylepadid barnacle, Microcorona girodi gen. et sp. nov., is described from lower and upper Campanian chalks of the Hannover area (northern Germany) and upper Maastrichtian biocalcarenites of southern Limburg (the Netherlands). The new taxon possesses a fused wall, comprising a rostrum, a carina, paired marginal plates and surrounding imbricating plates; an upper latus is absent. Cladistic analysis supports the interpretation that the new taxon is a sister group to all post-Mesozoic balanomorph barnacles (Neobalanomorpha). In the Hannover area, the new brachylepadid encrusted brachiopod shells, echinoid tests and serpulid tubes in a deep water (> 200 m) habitat. The single specimen from the upper Maastrichtian of the southern Netherlands was bioimmured by an exogyrine oyster in a shallow-water (< 50 m) setting, thus demonstrating that early balanomorphs were able to occupy a wide range of habitats.