The rodent assemblages from the Late Aragonian and the Vallesian (Middle to Late Miocene) of the Vallès-Penedès basin (Catalonia, Spain)

La conca del Valles-Penedes es una area clau per a lestudi de les successions de mamifers del Mioce europeu, donat que el seu abundant registre cobreix gairebe la totalitat daquest periode. Recentment, degut a les obres dampliacio de lAbocador de Can Mata (ACM), al terme municipal de Els Hostalets de Pierola (lAnoia, Barcelona), el nombre de jaciments coneguts de micro- i macromamifers sha duplicat. Lestudi de les faunes de micromamifers de la serie estratigrafica de lACM ha permes aportar importants dades bioestratigrafiques per a la definicio de les biozones MN 7 i MN 8, actualment basades en localitats aillades de Franca i Alemanya. Tambe es proposa una correlacio bioestratigrafica amb altres conques iberiques com Calataiud-Terol. Pel que fa als rosegadors de la serie de lACM, es descriu una nova especie de castorid: Chalicomys n. sp. Aquesta especie ja presenta un mode de locomocio aquatica molt similar al del castor actual. Durant les obres dampliacio de lACM es localitza un nou jaciment, Barranc de Can Vila 1 (BCV1), que, a mes duna abundant mostra de micro- i macrofauna, ha lliurat un esquelet remarcablement complet duna nova especie de gran antropomorf: Pierolapithecus catalaunicus. Lestudi dels rosegadors de BCV1 ha permes situar cronologicament aquesta localitat a la part baixa de la MN 7+8, entre els 12,5 i els 12 Ma. En consequencia aquesta localitat representa el registre mes antic dels grans antropomorfs a la Peninsula Iberica. Lestudi tafonomic de les restes recuperades a BCV1 revela que diferents agents tafonomics estigueren involucrats en la genesi de lacumulacio. Es reconeix la depredacio com el principal agent dacumulacio en el cas de lindividu de primat. Per contra lacumulacio de la majoria de la resta de fossils no sembla estar associada a laccio de depredadors i/o carronyaires. La fauna de micromamifers de BCV1 ens indica la presencia dun ambient forestal subtropical i humit en oposicio a lambient clarament mes sec i obert imperant a les conques de linterior dEspanya. Aquest fet podria explicar labsencia dantropomorfs a aquestes arees durant el Mioce. Seguidament es compara la composicio i estructura de la taxocenosi de rosegadors de lAragonia terminal i del Vallesia de la conca del Valles-Penedes amb la dues conques iberiques (Calataiud-Terol i Duero). Els resultats dels analisis estadistics multivariants mostren que les paleocomunitats de rosegadors de la conca del Valles-Penedes son marcadament diferents de les de les conques de linterior dEspanya durant la major part de linterval de temps considerat. Lambient al Valles-Penedes sembla que fou mes humit i boscos, assimilant-se a lexistent a zones mes septentrionals. Al limit entre el Vallesia Inferior i el Superior (vers fa 9,7 milions danys) les paleocomunitats de rosegadors canvien bruscament a totes les conques. Aquest periode es testimoni dun canvi vers a associacions menys diverses i dominades per un o uns pocs generes. La diferenciacio biogeografica existent a la Peninsula Iberica es mante i fins hi tot incrementa durant el Vallesia Superior. Aquest canvi abrupte es coneix com la Crisi Vallesiana i tambe afecta a les comunitats de macromamifers, implicant en ambdos casos lextincio de formes propies del Mioce Mitja adaptades a ambients calids i boscosos i resultant en un descens en la diversitat. Mitjancant diferents tecniques es mostra que aquest esdeveniment dextincio no es va estendre a altres arees dEuropa, on la diversitat es va mantenir estable o fins hi tot va incrementar. The Valles-Penedes Basin is a crucial area for the study of the mammal succession of the European Miocene, since its abundant record covers nearly the totality of this period. Recently, thanks to the extension works of a rubbish dump, the so-called Abocador de Can Mata (ACM) at Els Hostalets de Pierola (lAnoia, Barcelona), the number of known micro- and macromammal sites has doubled. The study of the micromammal faunas of the stratigraphic series of the ACM has added important data for the definition of the biozones MN 7 and MN 8, which now are based in isolated sites from France and Germany. We have also proposed biostratigraphic correlation for the Late Aragonian of the Valles-Penedes Basin to other Iberian basins such as Calatayud-Teruel. Concerning the rodents of the ACM series, a new species of castorid is described: Chalicomys n. sp. This species already shows a mode of aquatic locomotion very similar to that of the extant beaver. A new site which has yielded an abundant sample of micro- and macrofauna, Barranc de Can Vila 1 (BCV1), was discovered during the extension works of the ACM. This site has also provided a remarkably complete skeleton of a new species of great ape: Pierolapithecus catalaunicus. The study of the rodents of BCV1 allows us to chronologically place this site in the lower part of MN 7+8, that is between 12.5 and 12 Ma. Accordingly this locality represents the oldest record of great apes in the Iberian Peninsula. The taphonomical study of the remains recovered at BCV1 reveals that different taphonomical agents were involved in the origin of the accumulation. Predation is recognized as the main accumulation agent in the case of the primate individual. In contrast, the accumulation of the rest of the fossils does not seem related to the action of predators and/or scavengers. The micromammal fauna from BCV1 indicates the presence of a humid subtropical forest environment as opposed to the clearly dryer an more open environment dominant in inner Spanish basins. This fact may account for the absence of great apes in those areas during the Miocene. Straight after that the composition and structure of rodent taxocenosis from the latest Aragonian and the Vallesian of the Valles-Penedes Basin is compared with those of two Iberian basins (Calatayud-Teruel and Duero). The results of the multivariate statistic analyses show that the rodent paleocommunities of the Valles-Penedes are markedly different from those of the inner Spanish basins during most of the considered time span. The environment in the Valles-Penedes Basin appears to have been more humid and forested, being similar to that occurring at higher latitudes. At the Early/Late Vallesian boundary (at 9.7 Ma) an abrupt change in the rodent paleocommunities of all the basins is recorded. This period witnesses a shift towards lower-diversity faunas dominated by one or a few genera. The biogeographic differentiation existing in the Iberian Peninsula is retained and even increases during the Late Vallesian. This abrupt change is known as the Vallesian Crisis and also affected the macromammal communities, implying in both cases the extinction of forms of characteristic of the Middle Miocene and adapted to warm forest environments. That ultimately resulted in a decrease of diversity. By the means of different techniques we show that this extinction event did not affected other areas of Europe, where diversity remained stable or even increased.