Fossil Lake deposits features some of the earliest known fossils of passerines—perching "songbirds." Called Zygodactylids, early members of this family had two toes in front and two in back, but living passerines have three toes in front and one in back.
This beautifully complete skeleton of Eozygodactylus americanus has the characteristic dainty beak of its species. It probably fed mostly on insects that swarmed the shoreline of ancient Fossil Lake.
Specimen: Eozygodactylus americanus, FMNH PA726
Locality: Fossil Butte Member of Green River Formation
Credit: © The Field Museum, GEO86416_072d, Photographer Dov Scher