The late Cenozoic history of the ostriches (Aves: Struthionidae), as revealed by fossil eggshell and bone remains

Ostriches (Struthionidae) are iconic Old-World giant flightless birds. The two living African species represent only a small part of ancient struthionid diversity, which comprises a number of fossil taxa, including the largest known birds of Northern Hemisphere – Pleistocene giants Pachystruthio. In comparison with most other birds, ostriches have an extensive fossil record, mostly represented by eggshell fossils, which are rather common in many Neogene to Quaternary localities of Africa and Eurasia. The global Old-World diversity of the fossil ostrich eggshell is here for the first time analyzed and put together with bone fossil record as well as current palaeoenvironmental and stratigraphic/biochronological data. The available fossil record indicates a complicated geographical pattern of ostrich evolutionary history during the Miocene, Pliocene and Pleistocene of Africa and Eurasia, with a number of evolutionary transformations and proposed dispersal events (both out-of-Africa and out-of-Eurasia). The evolution of ostriches is further put into a context of the overall environmental and faunal evolution, and paleontology-based hypotheses of the origin of modern taxa are developed.