A partial skeleton of a new species of Tynskya Mayr, 2000 (Aves, Messelasturidae) from the London Clay highlights the osteological distinctness of a poorly known early Eocene “owl/parrot mosaic”

Abstract Tynskya eocaena is an early Eocene bird with a raptor-like skull and semi-zygodactyl feet, whose description based on skeleton from the North American Green River Formation. In present study, three-dimensionally preserved bones of new species , T. waltonensis are reported London Clay Walton-on-the-Naze (Essex, UK). The fossils belong to single individual provide insights into skeletal morphology messelasturids. particular, they reveal unusual vertebral specializations, cervical vertebrae having concave rather than saddle-shaped caudal articulation facets caudalmost thoracic vertebra being platycoelous (flat articular surfaces). very deep mandible derived ungual phalanges support sister group relationship between taxon Messelastur (Messelasturidae). Phylogenetic analyses emended data matrix did not conclusively resolve higher-level affinities messelasturids closely related halcyornithids, both taxa sharing characters only distantly extant (Accipitriformes, Strigiformes, Falconiformes, Psittaciformes). An analysis that was constrained molecular scaffold, however, recovered as clade including psittaciform passeriform birds. morphologies suggest specialized feeding adaptations may have exploited niche, which no longer available