Psittacopedids and zygodactylids: The diverse and species-rich psittacopasserine birds from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK)

The Daniels collection of fossil birds from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK) contains multiple specimens of the Psittacopedidae and Zygodactylidae, which are here for the first time studied in detail. The Psittacopedidae include Parapsittacopes bergdahli, Psittacomimus eos, gen. et sp. nov., ?Psittacopes occidentalis, sp. nov., and at least one further unnamed species. The Zygodactylidae comprise Primozygodactylus cf. danielsi, Primoscens cf. minutus, Primoscens carolinae, sp. nov., as well as several unnamed species, which are represented by fragmentary remains. A very small zygodactylid-like species, which was previously identified as P. minutus, is described as Minutornis primoscenoides, gen. et sp. nov. A phylogenetic analysis showed the Zygodactylidae and Psittacopedidae to be stem group representatives of the Passeriformes (passerines), but the exact interrelationships of the fossil taxa are poorly resolved. In particular, no compelling character evidence supports a monophyletic Zygodactylidae, with distinctive features of these birds being likely to be plesiomorphic for Psittacopasseres or also found in crown group Passeriformes. In the majority rule consensus tree of our analysis, Minutornis is the sister taxon of a clade including the Zygodactylidae and Passeriformes, whereas the affinities of the Psittacopedidae were insufficiently resolved http://zoobank.org/urn:lsid:zoobank.org:pub:81800349-5DE9-468B-81D7-6A5664526DF1.

Automated summary

This study provides a detailed analysis of the fossil birds from the early Eocene London Clay, focusing on the Psittacopedidae and Zygodactylidae specimens. The study suggests that these fossil species may represent stem group representatives of the Passeriformes (passerines), but the exact relationships between them are still unclear.