New Bird Taxa (Aves: Galliformes, Gruiformes) from the Early Eocene of Mongolia

New bird taxa are described from the early Eocene Bumban Member of the Tsagaan-Khushuu locality in southern Mongolia. Bumbanortyx transitoria gen. et sp. nov. is a small galliform bird that combines morphological similarity with the fossil families Quercymegapodiidae and Gallinuloididae. The somewhat larger Bumbanipodius magnus gen. et sp. nov. also shows similarities with Quercymegapodiidae, but is close to Argillipes aurorum from the early Eocene of England in the structure of the tarsometatarsus. Bumbanipes aramoides gen. et sp. nov. shows the greatest similarity with modern Aramidae (Gruiformes). Bumbaniralla walbeckornithoides gen. et sp. nov. is described based on a coracoid, morphologically intermediate between those of Walbeckornis and Messelornithidae (stem Gruiformes). The presence of unnamed Messelornithidae in the fauna of the Tsagaan-Khushuu locality is also noted.