Gerpegezhus daniaoriundus sp. nov.: a new species of centriscoid fish (Gerpegezhidae) from the Eocene Fur Formation of Denmark

A new species of syngnathiform fish, Gerpegezhus daniaoriundus n. sp., from the Eocene Fur Formation of Denmark is described herein. The description is based on 17 specimens preserved in either soft diatomite or carbonate concretions. The two lithologies result in different preservation of the morphological features. Gerpegezhus daniaoriundus n. sp. exhibits a set of diagnostic features of the extinct monotypic family Gerpegezhidae and of the genus Gerpegezhus, including (1) greatly elongated body, (2) presence of ossified myoseptal tendons, (3) lower procurrent caudal-fin rays absent, (4) dorsal- and anal-fin spines absent, and (5) pelvic fin and girdle absent. It can be separated from the species Gerpegezhus paviai by having a much slenderer body bearing unpaired leaf-like appendages protruding from its ventral side, and completely different meristic values, including up to 39 (or 40) vertebrae, a total of 16 unbranched caudal-fin rays, dorsal and anal fins with 5 and 16 unbranched rays, respectively, and a different organization of body armor comprising two dorsal bilateral series of dermal plates. The occurrence of the genus Gerpegezhus from the Fur Formation provides a remarkable example of the biogeographic relationships between the North Sea realm and the Tethys in the earliest Eocene.