A new beardfish (Teleostei, Polymixiiformes) from the Eocene Fur Formation, Denmark

Abstract

The earliest Eocene (Ypresian) Fur Formation (Denmark) is globally renowned for its exceptionally well-preserved fossils, including birds, sea turtles, insects, plants, andfishes. Fishes, albeit abundant and diverse, however, areonly superficially known and very few detailed, taxonomic studies have been realized to date. A new polymixiiformfish,Polyspinatusflueregen. et sp. nov., from the Fur Formation is described based on seven well-preserved, nearly completespecimens. All the specimens were studied by traditional stereomicroscopy, and by micro-X-rayfluorescence-elementmapping. Digital 2D-element images of strontium-, phosphorus-, and calcium distributions of each specimen were directlyapplied for the taxonomic descriptions presented herein.Polyspinatusflueregen. et sp. nov. is thefirst known Eocenerecord of the family Polymixiidae based on articulated skeletal remains.Polyspinatusgen. nov. exhibits a uniquecombination of characters that support its recognition as a new genus of the Polymixiidae. Its specialized hyoid apparatuswith thefirst and second branchiostegal rays being sinuous and parallel to each other, and the third being wide and plate-like, followed by four saber-like elements, is strikingly similar to that ofPolymixia, supporting a possible sister-grouprelationship with extant beardfishes.