Tracks of a Stilt-Like Bird from the Early Eocene Green River Formation of Utah: Possible Earliest Evidence of the Recurvirostridae (Charadriiformes)

Abstract

Abstract. Three avian footprints from a well-known early Eocene fossil track locality in Utah appear to represent an otherwise unknown stilt-like bird, possibly referable to the Recurvirostridae. The bird that made these tracks had very long legs but relatively short toes and was probably somewhat smaller than modern stilts (Himantopus). There was a vestigial hind toe and the feet were webbed, but the webbing was reduced more than in Recurvirostra or Cladorhynchus, but not nearly as much as in Himantopus. This may constitute the oldest evidence yet found of a recurvirostid-like bird, although the family probably originated even earlier if it gave rise to flamingos (Phoenicopteridae), which were already in existence by the early and middle Eocene.