Votre navigateur n’affiche pas l’aperçu PDF. Ouvrir le PDF →

Résumé

The La Parte site, northern Spain, contains a cold-adapted faunal assemblage preserved in a horizon radiometrically dated to a minimum age of 150 ka. It represents the most ancient site with cold resistant fauna in the Iberian Peninsula. Among the species recorded in La Parte, two represent the typical cold-adapted large mammal association, following Kahlke (1999) who only considers those species inhabiting the arctic to subarctic or inner-continental regions: Coelodonta antiquitatis and Rangifer tarandus. The presence of the Woolly Rhino at La Parte makes this site specially important for a number of reasons, this taxon can provide relevant environmental information about the Mammoth Steppe and furthermore La Parte is placed in the Middle Pleistocene, when this species is not as abundant as during the Late Pleistocene, so its cold-adapted features can be studied from an evolutionary perspective. The remains attributed to Rangifer tarandus also recovered from this site, suggest an open woodland ecosystem. The presence of Marmota sp. In the same level is confirmed at La Parte based on a fragmentary humerus, and could suggest an alpine or periglacial ecosystem. Nevertheless, recent results do not support the correlation between phylogeny and climatic tolerance for extant species of Marmota (Lopez and Cuenca 2002). In some Middle Pleistocene sites, remains of Hystrix vinogradovi have been recovered in association with Marmota marmota and, based on this evidence, it is questioned whether Hystrix and Marmota are valuable climatic indicators (Cuenca-Bescos et al.1999), at least in the Iberian Middle Pleistocene. The presence of Marmota in the La Parte site suggests an open landscape with cold conditions. The rest of the taxa included in the La Parte assemblage (Crocuta crocuta, Panthera leo, Cervus elaphus, Megaloceros cf. giganteus, Bison priscus and Equus caballus) are usually associated with typical cold-adapted faunas, but they are also found in woody temperate zones so these do not in themselves characterise a cold period. The faunal association from La Parte suggests a combination of steppic and open woodland ecological conditions. The level containing the faunal remains is included in a karstic complex cavity. The construction of a highway caused the destruction of part of the terrain surface and thus the discovery of such a cave filling. The ossiferous level is rich in speleothems which surround or fill the fossil bones. U-series analyses of two speleothems, which included several bone fragments, coming from the bone accumulation level, yielded dates of 188+11 ka and 141 +8 ka. Following these results obtained by the team of geochronologists who worked out the analyses (Institut de Ciencias de la Terra "Jaume Almera", Barcelona), the most likely minimal age for this level is 150 ka. The La Parte faunal association is biochronologically consistent with the end of the Middle Pleistocene, during a timespan that could correspond with oxygen isotope stage 6, a cold period. The origin of the bone accumulation seems to be related to a hyaena den. This is interpreted from a variety of evidence: almost the totality of the fossil remains correspond to herbivores, being mainly limb bones, which are the easiest to disarticulate and to transport into a cave furthermore, a high percentage of the bone assemblage presents puncture marks and gnawing damage produced by the spotted hyaena's dentition in addition, several coprolite accumulations, attributed to hyaenas, were discovered at all stratigraphic levels. Furthermore, a fragmentary P2 of a juvenile Crocuta crocuta was recovered, which also confirms the presence of this taxon. The cold-adapted taxa are considered rare in the Iberian Peninsula (when compared with other European countries), so any new faunal discovery is of relevance and provides important information related to the glacial mammalian