First evidence of ganoin-scaled Halecomorphi (Neopterygii) in the Lower Jurassic of Holzmaden and Ohmden, Germany

Abstract

The Posidonienschiefer Formation (lower Toarcian) of the Holzmaden region, Baden-Württemberg, in southwestern Germany is world- famous for its marine fossils, including excellently preserved fossil vertebrates, especially ichthyosaurs and plesiosaurs, but also fossil fishes. The study of the diversity and palaeoecology of fish within these deposits gives us further hints to understand the corresponding ecosystem. With Holzmadenfuro rebmanni new gen. et sp. and Ohmdenfuro bodmani new gen. et sp., both curated at the Urweltmuseum Hauff in Holzmaden, we now describe the first ganoin-scaled Halecomorphi from the Posidonienschiefer of Germany. These new taxa are characterized by a specific combination of features, including body shape; number of parietals, extrascapulars, infraorbitals, dorsal and caudal fin rays, and vertical scale rows; number and shape of maxillary teeth; number and arrangement of supraorbitals; ornamentation of skull bones; insertion of dorsal, pelvic, and anal fins; position of lateral line in caudal fin area; shape and distribution of scales; and number and shape of serrations on scales. The more basal Halecomorphi with ganoid scales (Parasemionoti- formes, Panxianichthyformes, and Ophiopsiformes) remain poorly known, compared with the more advanced halecomorph group of the Amiiformes (especially the Amiidae). Closer investigation of their taxonomic relationships is therefore important for understanding broader patterns of haleco- morph evolution, especially the origin of the Jurassic Ophiopsiformes.