Decoding the microvertebrate record in Alero Los Viscos (Catamarca, Argentina): a taphonomic investigation of the surface bone assemblage

CLAUDIA MONTALVO; MARIANA MONDINI; CAROLINA MADOZZO - JAEN; ANA CAROLINA MOREANO; FLORENCIA ARIAS

TARRAGONA

Encuentro; 3rd Meeting of the ICAZ Microvertebrate Working Group; 2020

Alero Los Viscos is an archaeological site located in El Bolsón Valley (Catamarca, Argentina), anarid region of the South-Central Andes, at 2470 m.a.s.l. It is a 380 m2rockshelter containingstonewalled structures, which was occupied since ca. 1220 BP. The faunal record includes manymicrovertebrate remains, especially on the modern surface and in the upper stratigraphic layers(dated to ca. 600-400 BP), where they may be intrusive. Use of the rockshelter by predator birdsand, to a lesser extent, carnivores is indicated by the presence of perches over the rocky walls andpellets and scats on the modern surface.Surface bones of rodents, birds, didelphids, armadillos, and anurans, accumulated over the last 600years at the most, display clear digestive traces. To help disentangle the complex formation historyof the most recent faunal record of the site and assess the actors involved, we performed ataphonomic analysis of 243 micromammal skeletal elements collected from the site modernsurface over different field seasons. We evaluated taxonomic and anatomical representation,relative abundance, and degree of breakage and digestion of the remains. Most bones belong torodents of the genera Ctenomys, Abrocoma, Microcavia, Andinomys, Calomys, and Phyllotis, anda few to the didelphid Thylamys, ranging 15-300g weight.All the taxa are known currently from the study area, although distributed in different habitats(grasslands, shrubs, and rocky areas). Relative abundance was 31.75% average, and cranialelements and femora were frequent. While several skulls, mandibles and postcranial elements werecomplete, remains with various categories of breakage were abundant. Light to no evidence ofdigestion was found in 58.71% remains, and several had moderate (16.07%) and extreme digestivemodification (6.67%). While breakage may be partly explained by trampling and other processes,digestion traces are more sensitive to the accumulating agent.433rd Meeting of the ICAZ Microvertebrate Working GroupTarragona (Spain) 1st ? 2nd September 2020The fact that light digestion is dominant suggests a Strigiform as the main accumulating actor. Yet,the presence of more intense digestion points to diurnal raptors and/or mammalian carnivores, andsuggests that the formation of the assemblage is complex and involves several agents. The modalinvolvement of a nocturnal raptor is in agreement with the findings in a nearby rockshelter, Cuevade las Máscaras, where a dense natural accumulation of digested skeletal elements was interpretedto be an owl pellet accumulation, possibly by Tyto furcata. By adding to our knowledge of thetaphonomic signature of Strigiformes in this Andean area, our study will help unravel the complextaphonomic history of archaeological sites in the El Bolsón Valley, particularly of Alero LosViscos, where more than half of the zooarchaeological material recovered from the upper layersare microvertebrates.