Halcyornithidae

Halcyornithidae is an extinct family of telluravian birds thought to be closely related to the parrots (Psittaciformes) and songbirds (Passeriformes), and probably even more closely to the extinct Messelasturidae with which they are usually united in order Halcyornithiformes. Halcyornithids have been found in various Eocene formations in Europe and North America starting about 55 mya; slightly older remains (60 mya) may or may not belong to this family with certainty. Widespread and diverse in the Early Eocene of North America and Europe, halcyornithids are not found in locales later than the Middle Eocene, where they have so far been discovered in Central Europe only.

Halcyornithids were small, arboreal birds with zygodactyl feet, with two toes facing forwards and two facing back, a trait shared with other tree-dwelling families of Eocene birds like the Zygodactylidae and the messelasturids. The skull of halcyornithids features a ridge of bone above the eye called the supraorbital process, similar to birds of prey.