Data for: Early Eocene fossils elucidate the evolutionary history of the Charadriiformes (shorebirds and allies)

<p><span>We report charadriiform and charadriiform-like birds from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK). A partial skeleton of a small modern-type charadriiform is described as a new species, <em>Charadriisimilis</em> <em>essexensis</em>, gen. et sp. nov. and most closely resembles taxa of the Charadrii (plovers, stilts, oystercatchers, and other "wader-like" shorebirds). Affinities to this clade were also supported by phylogenetic analyses, which placed the fossil as the sister taxon of either the Burhinidae or all crown group Charadrii. In addition, we identify specimens of the charadriiform-like taxon <em>Scandiavis</em>, which was before only known from the early Eocene Fur Formation in Denmark. Associated limb elements of two individuals are classified as <em>Scandiavis</em> cf. <em>mikkelseni,</em> and remains of two further individuals are tentatively assigned to <em>Scandiavis</em>. The presence of a processus supracondylaris dorsalis on the previously unknown humerus corroborates charadriiform affinities of <em>Scandiavis</em>, whereas a plesiomorphic hypotarsus morphology indicates a position outside crown group Charadriiformes. <em>Charadriisimilis</em> <em>essexensis</em> is one of the earliest modern-type charadriiforms, and the holotype of the species is the most substantial early Paleogene fossil record of a charadriiform bird. Together with <em>Scandiavis</em>, as the </span><span>best-represented taxon to be considered as a</span><span> stem group charadriiform, it provides the basis for an improved understanding of the evolutionary history of charadriiform birds. </span></p>