"Clusters of differentiation" . "Miocene horses" . "Influenza A virus" . "Extant Miocene first appearances" . "Animal virology" . "Equidae" . "Infraspecific virus taxa" . "Zoonoses" . "Pleistocene horses" . "Influenza A virus subtype H1N1" . "HIV/AIDS" . "Pliocene odd-toed ungulates" .