The isotopic fingerprint of terrestrial gastropods has been increasingly used as a credible natural paleoenvironmental archive. Most published work has used this proxy at tropical and temperate latitudes of the Northern Hemisphere, and focused on entire-shell analysis. The present study provides entire-shell and intra-shell isotopic profiles to infer average and seasonal late Holocene environmental conditions in central Argentina (30°S). Shells of Plagiodontes daedaleus (Gastropoda: Odontostomidae) were retrieved from the Alero Deodoro Roca–Sector B site, one of the few archaeological sites in central Argentina rich in shells collected by pre-Hispanic hunter-gatherer groups. Ancient entire shells exhibited values that were ~2.5‰ higher in δ13C and ~1.8‰ higher in δ18O than modern individuals, pointing to higher abundance of C4 plants and overall drier conditions (lower relative humidity and/or higher rain δ18O) during 4.5–1.7 cal. kyr BP than today, in agreement with published regional proxies. Intra-shell isotopic profiles suggest that modern and fossil specimens deposited their shells throughout two-to-three summer/winter cycles. Intra-shell δ18O values varied ~5‰, matching with the seasonal variation of rain δ18O values. The extent of seasonality was similar during 4.5–1.7 cal. kyr BP and today. Intra-shell δ13C values varied ~2–3‰ and did not portray distinct seasonal cycles, depicting minimal seasonal variations in the snail diet. This work illustrates that South American terrestrial gastropods have great potential for paleoenvironmental studies.
Guanacos (Lama guanicoe) are large ungulates that have been valued by human populations in South America since the Late Pleistocene. Even though they were very abundant until the end of the 19th century (before the high deforestation rate of the last decades), guanacos have nearly disappeared in the Gran Chaco ecoregion, with relicts and isolated populations surviving in some areas, such as the shrubland area near the saline depressions of Córdoba province, Argentina. In this report, we present the first data from a locally endangered guanaco wild population, through the study of skeletal remains recovered in La Providencia ranch. Our results showed that most of the elements belonged to adults aged between 36 and 96 months; sex evaluation showed similar numbers of males and females. Statistical analysis of the body size of modern samples from Córdoba demonstrated that guanacos from the Chaco had large dimensions and presented lower size variability than the modern and archaeological specimens in our database. Moreover, they exhibited dimensions similar to those of modern guanacos from Patagonia and San Juan, and to archaeological specimens from Ongamira and Cerro Colorado, although further genetic studies are needed to corroborate a possible phylogenetic relationship. Finally, we used archaeozoological techniques to provide a first characterization of a relict guanaco population from the Chaco ecoregion, demonstrating its value to the study of modern skeletal remains and species conservation biology.
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