A new fossil species assigned to the galliform genus Paraortygoides Mayr is described from the Lower Eocene (Ypresian Stage) London Clay Formation of the United Kingdom. Paraortygoides radagasti, n. sp., is referred to the genus on the basis of comparisons with other specimens from the Middle Eocene deposit of Messel (Hessen, Germany). Because of the three-dimensional preservation of this fossil material, P. radagasti contributes new information pertaining to the morphology of the genus Paraortygoides, in particular with regard to the thoracic vertebrae, tarsometatarsus, and toes. This genus, for example, is distinguished from other currently known fossil and extant galliform birds by the presence of deep pneumatic excavations in the lateral sides of the thoracic vertebrae. The results of a preliminary phylogenetic analysis suggest that Paraortygoides is basal within Galliformes (as already proposed by Mayr [2000]); monophyly of the order is supported with Megapodiidae as the basal sister taxon with respect to the Cracidae and Phasianidae. Paraortygoides radagasti is one of the oldest galliform birds described to date; its age and degree of preservation provide a reliable early phylogenetic constraint for the divergence of a basal clade within the order Galliformes.