Demineralization of medium and megamammals bones from pampean region (Argentina and Uruguay)

CHICHKOYAN KARINA VANESA; ACUÑA SUAREZ GABRIEL; NAMI HUGO G.; AGUILAR JOSÉ LUIS

Congreso; 4th Palaeontological Virtual Congress; 2023

The causes of the extinction of Pampean taxa are still controversial. One of the main problems is the irregular conditions of collagen preservation, which difficult to understand diets and paleoenvironments. For that, this contribution will detail two demineralization methods applied to bones of medium and megamammalsin order to obtain collagen for stable isotope analysis(δ13C and δ15N). Bones of Xenarthra, Carnivores and Ungulates (N=25) from the last 30.000YBP were taken from 9 locations. Collagen was extracted in 11 samples but only3 provided isotopes (2 Equidae and one Glyptodon). For the first method 15 samples were diluted in 0.2M hydrochloric acid (HCl) and then in 0.1 M sodium hydroxide, then into the oven (60º). Only 6 bones did not dissolveand 2 were measured. Demineralization process was slowed for the second method.Twenty-five samples (the aforementioned 15 plus 10 new) were demineralized at 0.5M HCl at room temperature, then in the refrigerator at 4º. Nine were put in theoven (70º) with distillate water and 3 drops of 0.5 M HCl. After approximately15 days, 7 bones yielded collagen (5 new and 2 had yielded in the first try also). One provided δ13C and δ15N and 5 only δ13C(one was not measured). According to this and other studies, bone collagen is affected by humidity and temperatures of the Late Pleistocene and Holocene in this open-air region. An alternative is to measure the apatite fraction, a method insufficiently used in fossils of this chronology in the region.