The Rodent assemblages from the late Aragonian and the Vallesian (middle to late Miocene) of the Vallès-Penedès basin (Catalonia, Spain)

Consultable des del TDXTítol obtingut de la portada digitalitzadaLa conca del Vallès-Penedès es una àrea clau per a l'estudi de les successions de mamífers del Miocè europeu, donat que el seu abundant registre cobreix gairebé la totalitat d'aquest període. Recentment, degut a les obres d'ampliació de l'Abocador de Can Mata (ACM), al terme municipal de Els Hostalets de Pierola (l'Anoia, Barcelona), el nombre de jaciments coneguts de micro- i macromamífers s'ha duplicat. L'estudi de les faunes de micromamífers de la sèrie estratigràfica de l'ACM ha permès aportar importants dades bioestratigràfiques per a la definició de les biozones MN 7 i MN 8, actualment basades en localitats aïllades de França i Alemanya. També es proposa una correlació bioestratigràfica amb altres conques ibèriques com Calataiud-Terol. Pel que fa als rosegadors de la sèrie de l'ACM, es descriu una nova espècie de castòrid: Chalicomys n. sp. Aquesta espècie ja presenta un mode de locomoció aquàtica molt similar al del castor actual. Durant les obres d'ampliació de l'ACM es localitzà un nou jaciment, Barranc de Can Vila 1 (BCV1), que, a més d'una abundant mostra de micro- i macrofauna, ha lliurat un esquelet remarcablement complet d'una nova espècie de gran antropomorf: Pierolapithecus catalaunicus. L'estudi dels rosegadors de BCV1 ha permès situar cronològicament aquesta localitat a la part baixa de la MN 7+8, entre els 12,5 i els 12 Ma. En conseqüència aquesta localitat representa el registre més antic dels grans antropomorfs a la Península Ibèrica. L'estudi tafonòmic de les restes recuperades a BCV1 revela que diferents agents tafonòmics estigueren involucrats en la gènesi de l'acumulació. Es reconeix la depredació com el principal agent d'acumulació en el cas de l'individu de primat. Per contra l'acumulació de la majoria de la resta de fòssils no sembla estar associada a l'acció de depredadors i/o carronyaires. La fauna de micromamífers de BCV1 ens indica la presència d'un ambient forestal subtropical i humit en oposició a l'ambient clarament més sec i obert imperant a les conques de l'interior d'Espanya. Aquest fet podria explicar l'absència d'antropomorfs a aquestes àrees durant el Miocè. Seguidament es compara la composició i estructura de la taxocenosi de rosegadors de l'Aragonià terminal i del Vallesià de la conca del Vallès-Penedès amb la dues conques ibèriques (Calataiud-Terol i Duero). Els resultats dels anàlisis estadístics multivariants mostren que les paleocomunitats de rosegadors de la conca del Vallès-Penedès són marcadament diferents de les de les conques de l'interior d'Espanya durant la major part de l'interval de temps considerat. L'ambient al Vallès-Penedès sembla que fou més humit i boscós, assimilant-se a l'existent a zones més septentrionals. Al límit entre el Vallesià Inferior i el Superior (vers fa 9,7 milions d'anys) les paleocomunitats de rosegadors canvien bruscament a totes les conques. Aquest període és testimoni d'un canvi vers a associacions menys diverses i dominades per un o uns pocs gèneres. La diferenciació biogeogràfica existent a la Península Ibèrica es manté i fins hi tot incrementa durant el Vallesià Superior. Aquest canvi abrupte es coneix com la Crisi Vallesiana i també afectà a les comunitats de macromamífers, implicant en ambdós casos l'extinció de formes pròpies del Miocè Mitjà adaptades a ambients càlids i boscosos i resultant en un descens en la diversitat. Mitjançant diferents tècniques es mostra que aquest esdeveniment d'extinció no es va estendre a altres àrees d'Europa, on la diversitat es va mantenir estable o fins hi tot va incrementar.The Vallès-Penedès 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 (l'Anoia, 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 Vallès-Penedès 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 Vallès-Penedès 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 Vallès-Penedès are markedly different from those of the inner Spanish basins during most of the considered time span. The environment in the Vallès-Penedès 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

The never−ending problem of Miocene beaver taxonomy

The finds of Miocene beavers are not rare at all. Neverthe− less, in most localities these rodents are only represented by a few dental elements, so that large collections are only occa− sionally available to researchers. Hence, the description of sufficiently large samples, such as the recently published de− scription of Steneofiber depereti from Hambach 6C (NW Germany, MN5) by Mörs and Stefen (2010), deserves the greatest attention. After a comprehensive description and comparison of the material, these authors conclude that pre− vious citations of the beaver Chalicomys jaegeri from the MN4 to MN6 (early to middle Miocene) are misidentifica− tions of the genus Steneofiber. Following Stefen (2009), these authors further question the validity of all the known Chali− comys species from the later middle Miocene (MN7+8). We agree with these authors that the occurrence of C. jaegeri in the middle Miocene is doubtful, but we disagree with their arguments for the synonymization of several species. Here we address this point and discuss the taxonomic criteria for distinguishing both genera, further reviewing the taxonomy of the genus Chalicomys at the species level

An updated biostratigraphy for the late Aragonian and Vallesian of the Vallès-Penedès Basin (Catalonia)

The Vallès-Penedès Basin (Catalonia, Spain) is a classical area for the study of the Miocene land mammal faunas and includes one of the densest and most continuous records in Eurasia. Furthermore, it is the type area for the Vallesian European land mammal age. After decades of study a huge amount of bio- and magnetostratigraphic data have been collected, allowing an unprecedented dating accuracy. Here we provide an updated local biostratigraphy for the late Aragonian, Vallesian and Turolian of the Vallès-Penedès Basin. This new biostratigraphic scheme is almost exclusively based on fossil rodents, which are the most abundant and one of the best known mammal orders in the area. Our proposal represents a significant refinement compared to previous attempts and provides a formal diagnosis and description of each zone, as well as clear definition of boundaries and a reference locality and section. The chronology of zone boundaries and main bioevents is based on detailed magnetostratigraphic data. The defined biozones allow for the correlation of the sites without associated magnetostratigraphical data. Finally, the correlation of the Vallès-Penedès local zones with other detailed local biostratigraphies, such as those of the Calatayud-Montalbán and Teruel basins (east-central Spain) is discussed. The sequence and chronology of the main bioevents is roughly comparable, although the rodent succession and the structure of the assemblage show important differences between these areas

Ten years in the dump: An updated review of the Miocene primate-bearing localities from Abocador de Can Mata (NE Iberian Peninsula)

More than ten years of paleontological fieldwork during the enlargement of the Can Mata Landfill (Abocador de Can Mata [ACM]), in els Hostalets de Pierola (Vallès-Penedès Basin, NE Iberian Peninsula) led to the recovery of >60,000 Miocene vertebrate remains. The huge sampling effort (due to continuous surveillance of heavy machinery digging activity, coupled with manual excavation and screen-washing of sediments) enabled generally rare faunal elements such as pliopithecoid and hominoid primates to be found. Thanks to detailed litho-, bio- and magnetostratigraphic controls, accurate dating is possible for all the recovered primate remains from 19 of the 235 localities defined along the 234 m-thick composite stratigraphic sequence of the ACM. Here we report updated estimated (interpolated) ages for these paleontological localities and review the timing of the primate succession in this area. Our results indicate that the whole ACM sequence is late Aragonian in age (MN6 and MN7+8) and includes seven magnetozones that are correlated to subchrons C5Ar.1r to C5r.2r (ca. 12.6 to 11.4 Ma). Great apes (dryopithecines) are first recorded at 12.4-12.3 Ma, but most of the finds (Anoiapithecus, Pierolapithecus and Dryopithecus) cluster between 12.0 and 11.9 Ma, followed by some indeterminate dryopithecine remains between 11.7 and 11.6 Ma. Pliopithecoids first appear at 12.1 Ma, being subsequently represented by Pliopithecus between 11.9 and 11.7 Ma. The small-bodied hominoid Pliobates is the youngest ACM primate, with an estimated age of 11.6 Ma. Although these primates probably overlapped in time, their co-occurrence is recorded only twice, at 11.9 Ma (a dryopithecine with Pliopithecus) and at 11.6 Ma (a dryopithecine with Pliobates). The rare co-occurrence between great apes and small-bodied catarrhines might be attributable to sampling biases and/or to presumed diverging ecological preferences of these groups. In the future, more detailed analyses of the fauna recovered from the long and densely-sampled ACM sequence will hopefully throw new light on this long-standing, unresolved question

Palaeoenvironmental reconstruction of the late Miocene macroflora of La Bisbal d'Empordà (Catalonia, Spain). Comparison with small mammals

The late Miocene flora from La Bisbal d'Empordà (Catalonia, Spain) provides significant data for characterising the coastal vegetation from the north-eastern Iberian Peninsula during a key period in Neogene climatic evolution. To this end, a historical leaf collection from La Bisbal d'Empordà was re-examined, analysed from a palaeoenvironmental viewpoint and compared with data provided by the associated small mammal fauna. This flora dates from 9.6–9.7 Ma in age (early Tortonian) according to small mammal biostratigraphy. The fossil-bearing beds were deposited in the floodplain of a meandering river system. Three palaeoecological assemblages were recognized: 1) Helophytic plant stems related to a wetland community. 2) Torn leaves of Fraxinus sp., Ulmus sp., Zelkova sp., Cedrelospermum sp. Populus balsamoides, Alnus gaudinii, Carpinus sp., Platanus sp., Acer tricuspidatum, Daphnogene sp. and, Laurophyllum sp. which would have belonged to a riparian forest located beyond the wetland community, with Fraxinus being the plant growing in closest proximity; 3) Isolated complete Paliurus seeds, interpreted as mainly wind-transported, which provide evidence of an open and more arid landscape situated distally from the floodplain. The small mammal assemblages associated with this flora are consistent with this palaeoenvironmental interpretation. The paucity of small arboreal mammal taxa and insectivores suggests limited forested vegetation areas, while the more common terrestrial species indicate better developed open landscapes. Our results show a more heterogeneous environment than previously thought and that the riverine processes impinged the flora, somewhat limiting the climatic conclusions that might be derived from leaf physiognomic analyses such as CLAMP

The range and extent of the Vallesian Crisis (Late Miocene): new prospects based on the micromammal record from the Vallès-Penedès basin (Catalonia, Spain)

The Vallesian Crisis was initially recognized as a local event, which implied the extinction of certain rodent and artiodactyl genera coincidingwith the early/late Vallesian boundary (at 9.7 Ma). Following works increased the range and extent of this event to encompass allEurope and involve a great number of mammal taxa. Here, we analyze the Vallesian rodent and insectivore record of the Vallès-Penedèsbasin (Catalonia, Spain), where the crisis was first recognized. We show that the quality of the record before the crisis is comparativelymuch better than afterwards so diversity appears inflated and extinction rates are overrated. Accordingly, we used inferred taxon rangesand rarefaction to calculate new diversity measures independent of sample size. These measures virtually eliminate the Vallesian Crisis,showing that diversity somewhat decreased during the earliest late Vallesian and soon recovered afterwards. This is because it cannot bediscarded that several rare taxa, customarily said to have disappeared during the crisis, are in fact present. Amongst the rodents and insectivores,these taxa include genera that are generally rare and show a discontinuous record during the early Vallesian. These are presumedspecialists adapted to humid forested environments such as flying squirrels, beavers or certain dormice, most of them being only recordedwhen the sample size is large enough. Alternatively, these genera may have been associated to very specific habitats which, for an unknownreason, are not sampled during the late Vallesian. Our results cast serious doubts on the very existence of the Vallesian Crisis suggesting thatrather than an abrupt event a series of extinctions occurred during a longer time span. It has not been evaluated whether the same patternis observed in the case of large mammals and in other areas. However, our results show that biases introduced by the quality of the recordneed to be taken into account when assessing the extent of the event.La Crisis Vallesiense fue inicialmente definida como un fenómeno local que implicó la desaparición de ciertos géneros de roedores y artio­dáctilos coincidiendo con el límite entre Vallesiense inferior y superior (hace 9.7 Ma). Trabajos posteriores ampliaron el ámbito y alcance de este evento hasta incluir toda Europa e implicar un gran número de taxones de mamíferos. En este trabajo analizamos el registro Vallesiense de roedores e insectívoros de la cuenca del Vallès-Penedès (Cataluña, España), donde la crisis fue reconocida por primera vez. Se muestra que la calidad del registro fósil con anterioridad a la crisis es comparativamente mucho mejor que la de después de modo que se magnifica la diversidad y se exageran las tasas de extinción. Por lo tanto, se ha utilizado rarefacción y se han inferido rangos estratigráficos a fin de calcular nuevas medidas de diversidad independientes del tamaño de la muestra. Estas medidas eliminan virtualmente la Crisis Vallesiense, mostrando que la diversidad disminuyó a principios del Vallesiense superior para recuperarse poco después a finales de esta edad. Esto es debido a que no podemos descartar que diversos taxones poco abundantes, normalmente citados como víctimas de la crisis, estuvieran de hecho presentes. Entre los roedores e insectívoros dichos taxones incluyen géneros que son generalmente raros y que muestran un registro discontinuo durante el Vallesiense inferior. Se trata de supuestos especialistas adaptados a ambientes boscosos húmedos tales como ardillas voladoras, castores o ciertos lirones, la mayoría de los cuales sólo se encuentran cuando el tamaño de la muestra es lo suficientemente grande. Alternativamente, estos géneros podrían haber estado asociados a hábitats muy específicos que por algún motivo no están siendo muestrea­dos durante el Vallesiense superior. Nuestros resultados cuestionan seriamente la existencia de la Crisis Vallesiense y sugieren que en lugar de un evento abrupto podría tratarse de una serie de extinciones que habrían sucedido durante un período más largo. Queda pendiente de evaluación si el mismo patrón se observa en el caso de los grandes mamíferos y en otras áreas. No obstante nuestros resultados muestran que se deberían tomar en consideración las desviaciones introducidas por la calidad del registro al analizar el alcance de este evento

An updated biostratigraphy for the late Aragonian and the Vallesian of the Vallès-Penedès Basin (Catalonia)

The Vallès-Penedès Basin (Catalonia, Spain) is a classical area for the study of the Miocene land mammal faunas and includes one of the densest and most continuous records in Eurasia. Furthermore, it is the type area for the Vallesian European land mammal age. After decades of study a huge amount of bio- and magnetostratigraphic data have been collected, allowing an unprecedented dating accuracy. Here we provide an updated local biostratigraphy for the late Aragonian, Vallesian and Turolian of the Vallès-Penedès Basin. This new biostratigraphic scheme is almost exclusively based on fossil rodents, which are the most abundant and one of the best known mammal orders in the area. Our proposal represents a significant refinement compared to previous attempts and provides a formal diagnosis and description of each zone, as well as clear definition of boundaries and a reference locality and section. The chronology of zone boundaries and main bioevents is based on detailed magnetostratigraphic data. The defined biozones allow for the correlation of the sites without associated magnetostratigraphical data. Finally, the correlation of the Vallès-Penedès local zones with other detailed local biostratigraphies, such as those of the Calatayud-Montalbán and Teruel basins (east-central Spain) is discussed. The sequence and chronology of the main bioevents is roughly comparable, although the rodent succession and the structure of the assemblage show important differences between these areas

The primate fossil record in the Iberian Peninsula

During the last decade, new discoveries in several Iberian basins, together with the description of previously unpublished finds, have significantly increased the recorded paleodiversity of fossil Primates (Mammalia: Euarchonta) in the Iberian Peninsula. Here we provide an updated compendium of the primate fossil record in Iberia during the Cenozoic and further summarize the changes in primate paleo­diversity through time, which are then analyzed in the light of changing climatic conditions. Thanks to favorable climatic conditions, the highest diversity of Iberian primates was reached during the Eocene, thus reflecting the radiation of both adapoids and omomyoids; only a single plesiadapiform genus is in contrast recorded in the Iberian Peninsula. Near the Eocene-Oligocene boundary, paleoclimatic changes led to a primate diversity crisis and other faunal changes, although two Iberian omomyoids survived the Grande Coupure. From the Middle Miocene onwards, catarrhine primates are recorded in the Iberian Peninsula. During the Middle and Late Miocene, they are represented by pliopithecoids and hominoids, restricted to NE Iberia. The Miocene hominoids from Iberia are of utmost significance for understanding the Eurasian hominoid radiation and its role in the origins of the great-ape-and-human clade. Following the local extinction of these taxa during the early Late Miocene, due to progressively increased seasonality and concomitant changes in plant communities, cercopithecoids are also recorded in the Iberian Peninsula from the latest Miocene through the Plio-Pleistocene, although they finally became locally extinct, whereas hominoids are again represented by fossil humans during the Pleistocene.Durante la última década, nuevos descubrimientos en varias cuencas ibéricas, junto con la descripción de hallazgos previos inéditos, han incrementado significativamente la paleodiversidad de Primates fósiles (Mammalia: Euarchonta) registrada en la Península Ibérica. Proporcionamos aquí un compendio actualizado del registro fósil de los primates en Iberia durante el Cenozoico, y resumimos además los cambios en paleodiversidad de los primates a lo largo del tiempo a la luz de las condiciones climáticas cambiantes. Gracias a condiciones climáticas favorables, la diversidad más alta de primates ibéricos se produjo durante el Eoceno, reflejando así la radiación tanto de los adapoideos como de los omomioideos; en cambio, sólo un único género de plesiadapiformes se registra en la Península Ibérica. Hacia el límite Eoceno-Oligoceno, los cambios paleoclimáticos condujeron a una crisis de diversidad de los primates y otros cambios faunísticos, aunque dos omomioideos ibéricos sobrevivieron a la Grande Coupure. Del Mioceno Medio en adelante, los primates catarrinos se registran en la Península Ibérica. Durante el Mioceno Medio y Superior, están representados por pliopitecoideos y hominoideos, restringidos al NE de Iberia. Los hominoideos del Mioceno de Iberia son de gran importancia para comprender la radiación de los hominoideos eurasiáticos y su papel en los orígenes del clado de los grandes antropomorfos y los humanos. A continuación de la extinción local de estos taxones du­rante el Mioceno Superior inicial, debido al incremento progresivo de la estacionalidad así como a cambios en las comunidades vegetales, los cercopitecoideos también se registran en la Península Ibérica a partir del Mioceno más terminal en adelante. Los cercopitecoideos se registran en la Península Ibérica durante todo el Plio-Pleistoceno, aunque finalmente también se extinguieron localmente, mientras que los hominoideos vuelven a estar representados otra vez por los humanos fósiles durante el Pleistoceno

Bio- and magnetostratigraphic correlation of the Miocene primate bearing site of Castell de Barber a to the earliest Vallesian

Castell de Barberà, located in the Vallès-Penedès Basin (NE Iberian Peninsula), is one of the few European sites where pliopithecoids (Barberapithecus) and hominoids (cf. Dryopithecus) co-occur. The dating of this Miocene site has proven controversial. A latest Aragonian (MN7+8, ca. 11.88-11.18 Ma) age was long accepted by most authors, despite subsequent reports of hipparionin remains that signaled a Vallesian age. On the latter basis, Castell de Barberà was recently correlated to the early Vallesian (MN9, ca. 11.18-10.3 Ma) on tentative grounds. Uncertainties about the provenance of the Hippotherium material and the lack of magnetostratigraphic data precluded more accurate dating. After decades of inactivity, fieldwork was resumed in 2014-2015 at Castell de Barberà, including the original layer (CB-D) that in the past delivered most of the fossils. Here we report magnetostratigraphic results for the original outcrop and another nearby section. Our results indicate that CB-D is located in a normal polarity magnetozone at about midheight of a short (~20 m-thick) stratigraphic section. The composite magnetostratigraphic section (~50 m) has as many as four to six magnetozones. These multiple reversals, coupled with the in situ recovery of a Hippotherium humerus from CB-D in 2015, make it very unlikely the correlation of any of the sampled normal polarity magnetozones with the long normal polarity subchron C5n.2n (11.056-9.984 Ma), which is characteristic of the early Vallesian. Our results support instead a correlation of CB-D with C5r.1n (11.188-11.146 Ma), where the Aragonian/Vallesian boundary is situated, and therefore indicate an earliest Vallesian age of ~11.2 Ma for Castell de Barberà. Our results settle the longstanding debate about the Aragonian vs. Vallesian age of this site, which appears roughly coeval with the Creu de Conill 20 locality (11.18 Ma), where hipparionins are first recorded in the Vallès- Penedès Basi

The range and extent of the Vallesian Crisis (Late Miocene) : new prospects based on the micromammal record from the Vallès-Penedès basin (Catalonia, Spain)

The Vallesian Crisis was initially recognized as a local event, which implied the extinction of certain rodent and artiodactyl genera coinciding with the early/late Vallesian boundary (at 9.7 Ma). Following works increased the range and extent of this event to encompass all Europe and involve a great number of mammal taxa. Here, we analyze the Vallesian rodent and insectivore record of the Vallès-Penedès basin (Catalonia, Spain), where the crisis was first recognized. We show that the quality of the record before the crisis is comparatively much better than afterwards so diversity appears inflated and extinction rates are overrated. Accordingly, we used inferred taxon ranges and rarefaction to calculate new diversity measures independent of sample size. These measures virtually eliminate the Vallesian Crisis, showing that diversity somewhat decreased during the earliest late Vallesian and soon recovered afterwards. This is because it cannot be discarded that several rare taxa, customarily said to have disappeared during the crisis, are in fact present. Amongst the rodents and insectivores, these taxa include genera that are generally rare and show a discontinuous record during the early Vallesian. These are presumed specialists adapted to humid forested environments such as flying squirrels, beavers or certain dormice, most of them being only recorded when the sample size is large enough. Alternatively, these genera may have been associated to very specific habitats which, for an unknown reason, are not sampled during the late Vallesian. Our results cast serious doubts on the very existence of the Vallesian Crisis suggesting that rather than an abrupt event a series of extinctions occurred during a longer time span. It has not been evaluated whether the same pattern is observed in the case of large mammals and in other areas. However, our results show that biases introduced by the quality of the record need to be taken into account when assessing the extent of the event.La Crisis Vallesiense fue inicialmente definida como un fenómeno local que implicó la desaparición de ciertos géneros de roedores y artiodáctilos coincidiendo con el límite entre Vallesiense inferior y superior (hace 9.7 Ma). Trabajos posteriores ampliaron el ámbito y alcance de este evento hasta incluir toda Europa e implicar un gran número de taxones de mamíferos. En este trabajo analizamos el registro Vallesiense de roedores e insectívoros de la cuenca del Vallès-Penedès (Cataluña, España), donde la crisis fue reconocida por primera vez. Se muestra que la calidad del registro fósil con anterioridad a la crisis es comparativamente mucho mejor que la de después de modo que se magnifica la diversidad y se exageran las tasas de extinción. Por lo tanto, se ha utilizado rarefacción y se han inferido rangos estratigráficos a fin de calcular nuevas medidas de diversidad independientes del tamaño de la muestra. Estas medidas eliminan virtualmente la Crisis Vallesiense, mostrando que la diversidad disminuyó a principios del Vallesiense superior para recuperarse poco después a finales de esta edad. Esto es debido a que no podemos descartar que diversos taxones poco abundantes, normalmente citados como víctimas de la crisis, estuvieran de hecho presentes. Entre los roedores e insectívoros dichos taxones incluyen géneros que son generalmente raros y que muestran un registro discontinuo durante el Vallesiense inferior. Se trata de supuestos especialistas adaptados a ambientes boscosos húmedos tales como ardillas voladoras, castores o ciertos lirones, la mayoría de los cuales sólo se encuentran cuando el tamaño de la muestra es lo suficientemente grande. Alternativamente, estos géneros podrían haber estado asociados a hábitats muy específicos que por algún motivo no están siendo muestreados durante el Vallesiense superior. Nuestros resultados cuestionan seriamente la existencia de la Crisis Vallesiense y sugieren que en lugar de un evento abrupto podría tratarse de una serie de extinciones que habrían sucedido durante un período más largo. Queda pendiente de evaluación si el mismo patrón se observa en el caso de los grandes mamíferos y en otras áreas. No obstante nuestros resultados muestran que se deberían tomar en consideración las desviaciones introducidas por la calidad del registro al analizar el alcance de este evento