Parvigruidae (Aves, core Gruiformes) from the early Oligocene of Belgium
The avian taxon Parvigruidae includes poorly known early Oligocene core Gruiformes, which were considered to be most closely related to either Ralloidea (rails and allies) or Gruoidea (cranes and allies) by earlier authors. Previous fossils of these birds were found in southern France (Parvigrus pohli) and eastern Germany (Rupelrallus saxoniensis). Here, I describe remains of two parvigruid species from the Rupelian stratotype (Boom clay) in Belgium. The smaller of these are tentatively assigned to P. pohli, the larger specimens agree with R. saxoniensis in size but differ in some morphological details and are assigned to a new species, ?Rupelrallus belgicus, sp. nov. The new fossils show that parvigruids were an important part of the early Oligocene European avifauna and had a wide distribution across the continent. They further allow recognition of previously unknown osteological features, especially of the humerus and hypotarsus, which substantiate sister group relationship between Parvigruidae and crown group Gruoidea.