Fossil-diagenetic modifications in Toxodon platensis Owen, 1837 (Notoungulata, Toxodontidae) from the Late Pleistocene of Corrientes Province, Argentina

Fossil-diagenetic features, including mineralogical, geochemical and paleohistological aspects, present in ribs of Toxodon platensis Owen (Mammalia, Notoungulata, Toxodontidae) were analyzed. Remains were recovered from floodplain deposits of the Toropi/Yupoi Formation assigned to the Late Pleistocene, cropping out in Corrientes Province (Mesopotamian Region, Argentina). The main mineral components of the ribs include hydroxyapatite and dahllite. The black color identified on the outer surface of some remains is related to impregnations due to precipitation of iron oxides. Original bone microstructure shows good preservation, but numerous radial microcracks were identified in the secondary osteons of all specimens. Iron oxides fill most microstructural features (Havers and Volkmann canals, osteocyte lacunae and canaliculi) and radial microcracks, and also replaced diverse areas of the bone matrix. The obtained information allows interpreting that the taphonomic histories of these remains are closely related to the particular characteristics of the environment of preservation.