Avian feet, crocodilian food and the diversity of larger birds in the early Eocene of Messel

Abstract

The lower Eocene lacustrine sediments of the Messel fossil site in Germany yielded a very rich and diversified avifauna. Most of the well-preserved skeletons stem from small-sized birds, whereas complete specimens of larger avian species are rare. There exist, however, a number of isolated feet of larger birds, eight of which are described in the present study. Except for one, all of these specimens exhibit broken leg bones with missing ends, which suggests that they represent feeding remains of predators or scavengers. Crocodilians, which are very abundant and diversified in the fossil record of Messel, are the most likely candidates, and the preservation of the Messel feet corresponds well with that of unambiguous crocodilian feeding remains from the late Oligocene of Europe. The eight feet described in the present study belong to just as many different species, most of which are otherwise unknown in the fossil record of Messel. Except for one, all specimens probably are from terrestrial taxa. These fossils attest to a hidden diversity of medium-sized to large terrestrial birds in the Messel palaeoenvironment and a bias in the taphonomic composition of the bird community towards the remains of small to medium-sized avian species.