Two new species of larger gruiform and charadriiform birds from the London Clay of Walton-on-the-Naze (Essex, UK)

Abstract We report two larger gruiform and charadriiform birds from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK). Leg bones of a new species of the gruiform Parvigruidae are described as ? Parvigrus ypresiensis , sp. nov. and show previously unknown morphological details of parvigruids, especially regarding the proximal end of the tarsometatarsus. The new species is the earliest record of the Parvigruidae, which before was only known from the early Oligocene of France, Belgium, and Germany. With an age of about 55 million years, it is also one of the oldest – if not the oldest – records of the Gruoidea in general. Fragmentary wing and pectoral girdle bones of another bird are assigned to the Charadriiformes and described as Waltonius burhinoides , gen. et sp. nov. Compared to extant charadriiform birds, the new species is most similar to the Burhinidae, with which it shares a derived morphology of the carpometacarpus. In light of the fragmentary nature of the holotype we refrain from a definitive classification, but if our tentative assignment to the Burhinidae is confirmed by more fossils, the species would be the oldest fossil record of the Burhinidae.