Written in bones: palaeoclimate histotaphonomic history inferred from a complete Megatherium skeleton preserved in the Atacama Desert
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Date
2025
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Abstract
A nearly complete and relatively well-preserved skeleton of the giant ground sloth Megatherium sp. in the hyperarid core of the Atacama Desert reveals how climate related taphonomic processes drastically transformed these remains over time. The individual, semi-exposed in situ by wind erosion, was found in late Pleistocene palaeowetland sediments that formed during the Central Andean Pluvial Event. Several radiocarbon dates on bone bioapatite and car bonate tufas date the specimen to c. 16500calyrBP. Physi cal, organic, and inorganic traces were identified using histotaphonomic, mineralogical, and microscopic analyses (optical, scanning electron and petrographic microscopy, x-ray diffraction and FTIR-ATR). Surficial bones with rounded, polished surfaces due to wind erosion are well pre served, while buried bones are poorly preserved and structu rally weak due to an early phase of bioerosion, which was followed by desiccation revealed by micro-cracks. Iron and manganese were deposited under anoxic conditions, followed by carbonates such as sparite and micrites, which formed due to a drier context, resulting in the encrustation of these bones by halite and calcium sulfates in hyperarid conditions that continue to this day. These observations imply that the ground sloth lived in a much wetter environment compared to today and its remains were subsequently affected by anae robic wet cycles, an oxidizing sedimentary environment, and later an oxidizing hyperarid climate. In summary, the unra velled histotaphonomy is written in small fractions of bones which emerge as new proxies for understanding the complex palaeoclimatic history of the Atacama Desert.
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Megatherium, Diagenesis, Histotaphonomy, Atacama Desert, Pleistocene, Palaeowetland