†Cretohlezkus gen. nov. from Upper Cretaceous Burmese amber demonstrates ancient origins of suctorial mouthparts in Eucinetidae (Coleoptera: Scirtoidea)

Abstract

Eucinetidae is a small beetle family comprising only ten extant genera. Five of them have unusually modified mouthparts with a strongly transformed labium, which shows features interpreted as adaptations to suctorial feeding. Among the hyperdiverse Coleoptera, similar feeding adaptations are known only in several genera of Cerylonidae and Leiodidae. Fossils attributed to Eucinetidae or representing taxa presumably closely related to eucinetids are known from Lower Cretaceous of China and Upper Jurassic of Mongolia, but none of them shows modified mouthparts. The first fossil of a ‘suctorial eucinetid’, †Cretohlezkus alleni gen. et sp. nov., is reported in the present paper, based on a well-preserved specimen in Cenomanian Burmese amber. A preliminary phylogenetic analysis placed †Cretohlezkus near base of the monophyletic ‘suctorial eucinetid’ lineage, but branch support was too low to present a robust evolutionary hypothesis. The prementum of †Cretohlezkus is modified as strongly as that of extant members of this group, demonstrating early origins of still only speculative feeding habits of the ‘suctorial eucinetids’, which presumably use Myxomycetes or Basidiomycetes as the source of food.