#psittacomimus

Passeriform birds are by far the most species rich bird group today, representing half of all birds (That's about 6,000 species), which is utterly wild. But before true passerines, birds in the stem-passerine lineage were already diversifying into all sorts of niches. They are equally close relatives to parrots and passeriforms, as can be seen from their passeriform-like bodies and beaks as well as their parrot-like zygodactyl feet. They were likely a big part of the Paleogene morning chorus.

Eofrillingirostrum: This Psittacopedid bird had a strong finch-like beak that was used in eating hard seeds. It lived during the early Eocene of Europe and North America.

Parapsittacopes: Another member of psittacopedes, this bird had a short beak used to eat fruit and berries. It lived 50 million years ago, and its fossils were found in the London Clay formation.

Eozygodactylus: This large member of the Zygodactylid family had long legs with parrot-like feet. These birds lived in North America during the early Eocene, 50 million years ago.

Sororavis: This rather strange member of the stem-passeriforms was found from the Fur Formation of Denmark, around 50 million years ago.

Pumiliornis: A long beaked stem-passeriform from Messel lake, around 40 million years ago. It was the first known bird to have eaten nectar, using its long beak to get it from flowers.

Primozygodactylus: Another member of the Zygodactylid group which lived all over Europe during the Eocene, but is best known from Messel Lake.

Psittacopes: A Psittacopedid bird with short legs and parrot-like feet. This frugivorous bird lived in many parts of Europe during the Eocene.

Psittacomimus: A Psittacopedid bird from the London Clay formation, this bird had zygodactyl feet like parrots as well as a short, rounded beak for eating seeds and fruit.

(Type specimen of Psittacomimus eos [scale bar = 5 mm], from Mayr and Kitchener, 2022)

Meaning of name: Psittacomimus = Psittacus [genus of parrots including the African gray parrot] mimic [in Greek]; eos = dawn [in Greek, referring to its Eocene age]

Age: Eocene (Ypresian), 54.6‒55 million years ago

Where found: London Clay Formation, Essex, U.K.

How much is known: Two partial skeletons, including one that preserves the skull, and a partial right foot. Two other specimens preserving parts of the foot may also belong to this taxon.

Notes: Psittacomimus was a psittacopedid, a group of small Eocene birds that were originally thought to have been closely related to parrots. Like parrots, they had two toes pointing forward and two backward on each foot. However, more recent studies suggest that psittacopedids might have been more closely related to passeriform birds (songbirds and their kin), which instead have the typical condition of modern birds in which three toes face forward and one points back.

The type specimen of Psittacomimus had been previously described briefly in 1998. However, it was left unnamed as it was held in a private collection instead of a publicly accessible museum at the time. The specimen has since been donated to the National Museums Scotland, allowing for more comprehensive study. Psittacomimus was anatomically similar to Parapsittacopes, another psittacopedid known from the London Clay Formation, but was larger than the latter and differs from it in subtle skeletal details, especially in the wing and shoulder bones.