The galliform birds from the Lower Eocene London Clay of Walton-on-the-Naze (Essex, U.K.): New species suggest faunal connections to Asia

We report stem group Galliformes from the lower Eocene (Ypresian) London Clay of Walton-on-the-Naze (Essex, U.K.), which are among the oldest known fossils of galliform birds. The specimens are assigned to two new species, ?<i>Paraortygoides argillae</i>, sp. nov. and <i>Waltonortyx bumbanipodiides</i>, gen. et sp. nov. The latter is classified in a new family-level taxon, Waltonortygidae, fam. nov., which differs from other higher-level clades of stem group Galliformes in a proximo-distally narrow caput humeri and a short tuberculum dorsale of the humerus. With regard to these plesiomorphic features and a characteristic morphology of the coracoid, <i>Waltonortyx</i> is similar to early Eocene stem group Galliformes from Mongolia. Wing and pectoral girdle bones of a third, undetermined galliform from Walton-on-the-Naze resemble the Quercymegapodiidae; this fossil also shows a similarity to early Eocene galliforms from Mongolia. The affinities of “<i>Paraortygoides</i>” <i>radagasti</i> Dyke and Gulas, 2002, the only previously described putative galliform from Walton-on-the-Naze, are uncertain and neither its classification in the Galliformes nor its assignment to the taxon <i>Paraortygoides</i> are unequivocally established. For the first time we subjected a larger taxonomic sample of early Paleogene Galliformes to a formal analysis, and even though the resulting phylogenies were poorly resolved, they supported paraphyly of the Quercymegapodiidae, with the Early Miocene taxon <i>Ameripodius</i> being more closely related to the crown group than the late Eocene species of <i>Quercymegapodius</i>. <i>Waltonortyx bumbanipodiides</i> was recovered as the sister taxon of the Mongolian <i>Bumbanipodius transitoria</i>, which indicates early Paleogene dispersal events across the Turgai Strait.