A comprehensive bone inventory list of the giant flightless bird Gastornis geiselensis from the Eocene “Geiseltal Fossillagerstätte” (Saxony-Anhalt, Central Germany) is presented. The fossils can be attributed to five different vertebrate sites, excavated in
the Geiseltal mining area in the 1950s and late 1960s. The finds come from the “Unterkohle”, the “untere Mittelkohle” and from the “obere Mittelkohle” representing a duration of at least 3.5 million years. In the terrestrial Tertiary mammalian stratigraphy
the “Geiseltal – Unterkohle” is the reference locality for the Lower Middle Eocene (MP 11), whereas the “Geiseltal – untere Mittelkohle” (MP 12) and the “Geiseltal – obere Mittelkohle” (MP 13) are the reference localities for the Middle
Middle Eocene and the Upper Middle Eocene. A reappraisal carried out for all relevant bones identified a total number of nine individuals from the former Geiseltal mining area within a time span of 5-6 million years, covering in total MP 11 – MP 14, the latter representing the lowermost
Upper Eocene. A slight increase in size of a femur and in a tibiotarsus from different stratigraphical sites (MP 11, MP 13) came to light, possibly indicating an evolutionary trend in Gastornis geiselensis. However, the observed size differences could also be explained by intraspecific
variation or sexual dimorphism. Considering the small samples, this evolutionary trend is a tentative assumption. A review of the tarsometatarsus bones, represented by two lesser preserved specimens, clearly points to a comparatively short, wide and strong bone, supporting the more or less
clumsy bearing of Gastornis geiselensis and a ponderous mode of locomotion, because of its primitive tetradactyl feet. Therefore, it seems rather unlikely that Gastornis geiselensis was capable of active predation and hunting, but rather was a scavenger than a bone crusher. Other
authors suppose it was a plant eater, but the discussion is still ongoing.
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