Palaeoenvironmental analysis of the Aragonian (middle Miocene) mammalian faunas from the Madrid Basin based on body-size structure

As a consequence of the growth of the Antarctic ice-sheet during the middle Miocene, a global decrease of temperatures and an associated increase in aridity provoked several environmental changes all around the world. Such environmental variations can be detected in the continental record of the mammalian prey community structure using a synecological approach. Because of the good quality of its faunas, the rich Aragonian vertebrate fossil record from the Madrid Basin (Spain) appears as a good candidate to explore these environmental changes. In order to analyse the climatic evolution of the Iberian Peninsula associated to the Global Cooling Event, two classic palaeosynecological methodologies (cenograms and body size diversity), based on body-size community structure, were applied to 6 fossil sites from the Madrid Basin, ranging over 2 million years (15.5 – 13.5 Ma). To establish a comparative framework, we used the ecological faunal data from 100 modern localities uniformly distributed all around the world. Our palaeoenvironmental inference is based on multivariate discriminant analysis of the dataset containing both modern and fossil mammals. Finally, we can conclude that the Aragonian mammalian assemblage from the Madrid Basin showed a predominance of semiarid environments with pulses of higher aridity in biozones Dc, E and F associated with the Global Cooling Event of the middle Miocene.Como consecuencia del crecimiento del casquete polar Antártico, durante el Mioceno medio, se produjo un descenso global de la tem­peratura asociado a un aumento de la aridez. Este tipo de cambios ambientales pueden ser detectados en el registro continental, siguiendo un modelo sinecológico para analizar la estructura de las comunidades de las faunas de mamíferos herbívoros. Debido a la calidad de sus faunas, el registro fósil de las faunas de vertebrados del Aragoniense de la Cuenca de Madrid se antoja como un buen candidato para explorar estos patrones de cambio ambiental. Con el objetivo de analizar la evolución climática de la Península Ibérica asociada al evento de enfriamiento global durante este lapso temporal, dos metodologías paleosinecológicas clásicas (cenogramas y espectros de diversidad de tamaño corporal), basadas en la estructura de tamaños corporales de las comunidades de mamíferos, han sido aplicadas a la fauna de herbívoros fósiles presente en seis yacimientos de la Cuenca de Madrid, abarcando aproximadamente 2 millones de años (15.5 – 13.5 Ma). Se ha establecido un marco comparativo usando los datos ecológicos de la fauna de mamíferos presente en 100 localidades uniformemente distribuidas por todo el planeta. Esta inferencia paleoambiental está basada en la aplicación de análisis discriminante multivariante sobre el conjunto de datos de las faunas actuales y fósiles. Finalmente, las faunas de mamíferos del Aragoniense de la Comunidad de Madrid mostraron una predominancia de ambientes semiáridos con varios pulsos de mayor aridez en las biozonas Dc, E y F asociados al evento de enfriamiento global del Mioceno medio

Palaeoenvironmental analysis of the Aragonian (middle Miocene) mammalian faunas from the Madrid Basin based on body-size structure

As a consequence of the growth of the Antarctic ice-sheet during the middle Miocene, a global decrease of temperatures and an associated increase in aridity provoked several environmental changes all around the world. Such environmental variations can be detected in the continental record of the mammalian prey community structure using a synecological approach. Because of the good quality of its faunas, the rich Aragonian vertebrate fossil record from the Madrid Basin (Spain) appears as a good candidate to explore these environmental changes. In order to analyse the climatic evolution of the Iberian Peninsula associated to the Global Cooling Event, two classic palaeosynecological methodologies (cenograms and body size diversity), based on body-size community structure, were applied to 6 fossil sites from the Madrid Basin, ranging over 2 million years (15.5 – 13.5 Ma). To establish a comparative framework, we used the ecological faunal data from 100 modern localities uniformly distributed all around the world. Our palaeoenvironmental inference is based on multivariate discriminant analysis of the dataset containing both modern and fossil mammals. Finally, we can conclude that the Aragonian mammalian assemblage from the Madrid Basin showed a predominance of semiarid environments with pulses of higher aridity in biozones Dc, E and F associated with the Global Cooling Event of the middle Miocene

Dental microwear analysis in Gliridae (Rodentia): methodological issues and paleodiet inferences based on Armantomys from the Madrid Basin (Spain)

In the present study we analyze the microwear of the species included in the lineage Armantomys aragonensis-A. tricristatus of two samples from two middle Miocene localities from the Madrid Basin (El Cañaveral and Casa Montero). The methodological part of the study compares light stereomicroscope photographs from resin casts and Environmental Scanning Electron Microscope (ESEM) photographs from original material. Furthermore two regions of the tooth crown (the most lingual part of the anteroloph, and the most lingual part of the protoloph) and two homologous regions of first and second upper molars have been analyzed. The paleoecological part includes the results of the microwear analyses of the two species included in the lineage A. aragonensis-A. tricristatus. The replacement of A. aragonensis with A. tricristatus in the Madrid Basin occurred during the Middle Miocene Climate Transition (MMCT) and is marked by a change in dental morphology. Therefore, in order to infer changes in diet associated to a shift in the environment, we checked for correlations on microwear features between the two different morphologies of the species. The two methodologies tested, ESEM on original teeth and light stereomicroscopy on resin casts, showed similar results on microwear analysis in the glirid Armantomys. Besides, both regions of the tooth crown and dental elements showed the same microwear patterns. The substitution of the species included in the lineage Armantomys aragonensis-A. tricristatus might not imply a change in diet

Cañada : a new micromammal succession from the lower Vallesian and Turolian of the Daroca area Calatayud Montalbán basin, Spain)

A new section including nine stratigraphically superposed microvertebrate fossil localities from the Calatayud-Montalbán basin (Spain) is presented. The Cañada localities and the small mammal assemblages are described, allowing a biostratigraphical correlation with the lower Vallesian from the nearby section of Nombrevilla. The results of this work are important because they help to improve the time resolution of the lower Vallesian faunal record from the Daroca area and to precise their relative biostratigraphical position. In addition, the upper part of the Cañada section includes two Turolian faunas, increasing the poor record from this age in the Calatayud-Montalbán basin.Se da a conocer una nueva sección que incluye nueve yacimientos de microvertebrados en superposición estratigráfica en la Cuenca de Calatayud-Montalbán (España). Se describen las localidades de la sección de la Cañada y sus faunas de micromamíferos, lo que posibilita su correlación con el Vallesiense inferior de la cercana sección de Nombrevilla. Los resultados obtenidos en este trabajo son importantes debido a que ayudan a mejorar la resolución temporal del registro faunístico del Vallesiense inferior del área de Daroca, y a precisar su posición bioestratigráfica relativa. Por otra parte, el tramo superior de la sección de la Cañada incluye dos faunas del Turoliense que incrementan el escaso conocimiento del registro de esta edad en la Cuenca de Calatayud-Montalbán

RESEARCH ARTICLE Body-size structure of Central Iberian mammal fauna reveals semidesertic conditions during the middle Miocene Global Cooling Event

We developed new quantitative palaeoclimatic inference models based on the body-size structure of mammal faunas from the Old World tropics and applied them to the Somosaguas fossil site (middle Miocene, central Iberian Peninsula). Twenty-six mammal species have been described at this site, including proboscideans, ungulates, carnivores, insectivores, lagomorphs and rodents. Our analyses were based on multivariate and bivariate regression models correlating climatic data and body-size structure of 63 modern mammal assemblages from Sub-Saharan Africa and the Indian subcontinent. The results showed an average temperature of the coldest month higher than 26ÊC for the Somosaguas fossil site, a mean annual thermal amplitude around 10ÊC, a drought length of 10 months, and an annual total precipitation greater than 200 mm per year, which are climate conditions typical of an ecotonal zone between the savanna and desert biomes. These results are congruent with the aridity peaks described over the middle Aragonian of Spain and particularly in the local biozone E, which includes Somosaguas. The aridity increase detected in this biozone is associated with the Middle Miocene Global Cooling Event. The environment of Somosaguas around 14 Ma was similar to the current environment in the Sahel region of North Africa, the Horn of Africa, the boundary area between the Kalahari and the Namib in Southern Africa, south-central Arabia, or eastern Pakistan and northwestern India. The distribution of modern vegetation in these regions follows a complex mosaic of plant communities, dominated by scattered xerophilous shrublands, semidesert grasslands, and vegetation linked to seasonal watercourses and ponds.Peer reviewe