Review of Tridactyl Avian Footprints (Ichnofamily Avipedidae) with Emphasis on Type Material from the Miocene of the Carpathians (Ukraine, Hungary and Romania)

Numerous ichnotaxa (about 21 ichnogenera and 39 ichnospecies) have been proposed for fossil tridactyl avian footprints. The purpose of this contribution is to analyze type material from Ukraine of the first proposed tridactyl avian ichnogenus, Avipeda, and related ichnogenera from the Carpathians of Hungary and Romania (Aviadactyla, Ornithotarnocia, Passeripedia, and Carpathipeda). The criteria for erection of ichnofamilies, ichnogenera and ichnospecies of avian footprints are discussed. It is proposed that trackway features only be used for ichnospecies. The ichnofamily Avipedidae comprises essentially small leptodactylous avian footprints showing three digits directed forward, with digits united or separate proximally, and lacking web imprint. The type material of Avipeda is represented by small footprints (less than 30 mm in length) that are wider than they are long, showing large total divarication and near symmetry with respect to digit III. Examined material from the type series of Avipeda from the Miocene of Ukraine also contains tetradactyl bird footprints that are better compared with Gruipeda. Aviadactyla and Ornithotarnocia (from the Lower Miocene of Ipolytarnóc, Hungary) are considered potentially available, whereas Passeripedia is deemed unavailable. Carpathipeda (erected for material from the Miocene of Romania) is indistinguishable from Avipeda. Additional comparisons are necessary to evaluate the status of other tridactyl avian ichnotaxa.