First report of Oligocene vertebrate footprints from Iran

Mammalian and avian footprints documented from the Oligocene of the Khaf area, northeastern Iran, represent the first reported Oligocene vertebrates in the country. Avian and mammalian footprints are located on the upper bedding plane of two successive, medium-bedded, brownish litharenite sandstone layers. Layer one has more than 97 concave epirelief avian footprints that are arranged in 29 straight or curved trackways. Layer two contains dispersed mammalian footprints. The avian footprints include four slender digits with sharp tips, three oriented forward (II–IV), and one of them oriented backward (I). Metapodium imprints are visible in some footprints as isolated circular concavities. The avian footprints are attributed to Gruipeda intermedia. In order to establish this identification, we re-affirm the diagnostic features of Gruipeda, Iranipeda and Charadriipeda, and also re-evaluate the ichnospecies assigned to these ichnogenera. The mammalian footprints from the Khaf locality include Khafipus khadari nov. igen and nov. isp., which are large plantigrade footprints that have five dispersed digit imprints in the pes or manus and heel or digit imprints that are enclosed by circular ridges, which are disconnected from each other. Palaeotheriipus isp. is a tridactyl mammalian footprint that is large in the heel with forward oriented toe imprints. Platykopus isp. includes one footprint as a broad plantigrade impression with imprints of five connected digits. Avian footprints are attributed to anisodactyl shore birds and mammalian footprints are those of perissodactyls and large mammals such as ursid carnivores. The footprints from the Oligocene of Iran documented here add to a growing, but much understudied global record of Cenozoic tetrapod footprints and suggest a broad paleogeographic distribution of various, particularly avian, ichnogenera.