Narrow-beaked trogons from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK)

Abstract

We describe multiple partial skeletons of a new trogon species from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK), which are among the oldest fossils of the Trogoniformes. Eotrogon stenorhynchus, gen. et sp. nov. has a much narrower and more gracile beak than extant trogons, which denotes different ecological attributes of the fossil species. Eotrogon stenorhynchus already had the heterodactyl foot characterising extant trogons, even though the trochlea for the second toe is smaller than in crown group Trogoniformes. Differences to extant trogons in the wing and pectoral girdle elements suggest that E. stenorhynchus was less adapted to short-term hovering, which may indicate different foraging techniques. We also report a partial tarsometatarsus from the early Miocene of France that is likely to belong to Paratrogon gallicus, a species previously only known from humeri. P. gallicus is the earliest modern-type trogon, and we show that the newly identified tarsometatarsus does not support the proposed referral of this species to the African taxon Apaloderma. We identify skeletal features that suggest a sister group relationship between Apaloderma and all other crown group Trogoniformes, but the exact affinities of Paratrogon remain poorly resolved. (http://zoobank.org/urn:lsid:zoobank.org:pub:73B64B84-11C2-4D50-8540-099CF86B6CA1).