MINERALOGY, GEOCHEMISTRY AND PALEOHISTOLOGY OF PLIOCENE MAMMALS FROM THE MONTE HERMOSO FORMATION (ARGENTINA). PAEDOTHERIUM BONAERENSE (NOTOUNGULATA, HEGETOTHERIIDAE) AS A CASE STUDY

Rodrigo Leandro Tomassini, Claudia Inés Montalvo, Teresa Manera, Graciela Visconti

Abstract


We describe and analyze the mineralogical, geochemical and paleohistological characteristics present in hemimandibles of
Paedotherium bonaerense (Ameghino) (Mammalia, Notoungulata, Hegetotheriidae). Remains were recovered from floodplain deposits of the
Monte Hermoso Formation (early Pliocene). Francolite is the main mineral component in all hemimandibles, evidencing compositional
changes in the internal crystalline structure during fossil-diagenesis. The similarity in the chemical composition of the fossils and the hosting
rocks suggests that the enrichment of the remains with new elements was due to direct exchange with the sediments in which they were buried.
Original bone microstructure shows good preservation, only affected by
permineralization and microfissures. Manganese and iron oxides are
the most abundant minerals infilling microstructural features and microfissures. The dark color identified on the outer surface of some
remains is related to precipitation of manganese oxides. The results
obtained allow us to establish the processes affecting the remains
before and after burial, and thus interpret the different taphonomic histories. This work provides new information on a issue usually not
considered in studies on vertebrate communities from the South
American Neogene and at the same time it establishes a framework
for the analysis of assemblages with similar characteristics.

Keywords


taphonomy; mammals; Paedotherium bonaerense; Pliocene; Argentina

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DOI: http://dx.doi.org/10.5710/AMEGH.01.07.2014.2737