Paleoecología del género Anchitherium von Meyer, 1834 (Equidae, Perissodactyla, Mammalia) en España: evidencias a partir de las faunas de macromamíferos

En el presente trabajo se interpreta la paleoecología y evolución del équido Anchitherium VON MEYER, 1834 por medio del análisis multifactorial (análisis de componentes principales, análisis discriminante) de las faunas de macromamíferos del Rambliense-Vallesiense inferior de la Península Ibérica. El análisis conjunto con faunas tropicales y subtropicales actuales permite inferir algunas de las características ambientales (temperatura, estacionalidad térmica) bajo las cuales se desarrollan dichas comunidades del Mioceno. Los resultados obtenidos también muestran la posibilidad de interpretar el bioma de una localidad en función de su fauna de macromamíferos, pudiéndose inferir la presencia en el Mioceno ibérico de laurisilvas, bosques tropicales y sabanas. Se observa una relación entre el tamaño relativo de la dentición respecto al tamaño corporal de Anchitherium y las variaciones en la temperatura. Las poblaciones que ocupaban ambientes térmicamente más estacionales presentaban una dentición relativamente mayor respecto al tamaño corporal que las habitantes de ambientes menos estacionales. Esto podría estar relacionado con un menor consumo de frutos determinado por una disminución en la disponibilidad anual de los mismos en las zonas con mayor estacionalidad térmica y un aumento en el consumo de follaje, menos nutritivo. La abundancia relativa de Anchitherium en los yacimientos parece determinada principalmente por las condiciones de temperatura, siendo más abundante cuanto menor es esta. Este hecho podría estar relacionado con las condiciones ambientales que los Anchitheriinae tuvieron que superar para atravesar Beringia antes de alcanzar Eurasia. Se estudian los biomas ocupados por cada especie de Anchitherium. Los dos clados propuestos por SÁNCHEZ et al. (1998) muestran un comportamiento similar. Especies más o menos ubiquistas y adaptadas a ambientes forestales densos dan lugar a especies más derivadas y adaptadas en mayor medida a los ambientes con una estación seca (bosques tropicales y sabanas), predominantes en la Península Ibérica durante el período estudiado. Este proceso es más acusado en el segundo linaje que en el primero. Durante la zona MN 6, una especie ubiquista, el inmigrante norteño A. hippoides entra en la península y sustituye a las especies presentes hasta el momento. Este proceso se relaciona con un progresivo aumento de la humedad ambiental que provocaría una reorganización de la fauna. Finalmente se expone un escenario ambiental para la evolución de Anchitherium en España. En él se muestra la relación de alternancia existente entre Equidae y Rhinocerotidae como grupo faunístico dominante durante el Mioceno. [ABSTRACT] The paleoecology and evolution of the equid Anchitherium VON MEYER, 1834 is studied in this paper by means of multifactorial analysis (principal components analysis, discriminant analysis) of the Ramblian-lower Vallesian large mammal faunas from the Iberian Peninsula. Joint analysis of subtropical and tropical recent faunas and Miocene faunas allow the establishment of several environmental characteristics (temperature, thermal seasonality) of the ecosystems of those Miocene communities. Our results indicate that it is possible to infer the biome of a locality based on its macromammal fauna. It has been able to infer the presence in the Iberian Miocene of temperate evergreen forests, tropical deciduous forests and savannas. A relationship is observed between the relative size of the dentition regarding the corporal size in Anchitherium and the temperature variations. Populations that occupied more thermally seasonal environments presented a relatively bigger dentition regarding their corporal size than the non-seasonally environment inhabitants. This could be related with a diminished consumption of fruits caused by a lesser fruit availability in the more thermal seasonality areas, and a higher consumption of leaves, less nutritive than fruits. The relative abundance of Anchitherium in the fossil local faunas seems mainly settled by temperature, being more abundant in faunas from colder fossil sites. This fact could be related with the environmental conditions that Anchitheriinae had to overcome to cross Beringia before reaching Eurasia. Biomes occupied by each Anchitherium species are studied. The two clades proposed by SÁNCHEZ et al. (1998) shown a similar behaviour. More or less ubiquitous species, adapted to dense forest environments, are substituted by more derived species adapted to ecosystems with a dry station (tropical deciduous forests and savannas), the predominant biomes in the Iberian Peninsula during the studied period. This process is more pronounced in the second lineage than in the first one. Another ubiquitous species, the northern immigrant A. hippoides come into the Iberian Peninsula in MN 6 zone and replace the rest of species. This process is related with the progressive increment in environmental humidity causing a faunal reorganization. Finally an environmental scenario for the evolution of Anchitherium in Spain is exposed. An alternation relationship as faunal dominant group during the Miocene between Equidae and Rhinocerotidae is shown

The muscle-powered bite of allosaurus (dinosauria; theropoda): an interpretation of cranio-dental morphology

11 pages, 7 figures.[EN] The skull morphology of Allosaurus has been the subject of functional interpretations which imply a predatory behaviour radically different from that recorded in any predatory land vertebrate. Those interpretations imply the use of the skull and maxillary dentition as analogues of hand-held, man-made weapons, incorporating the inertia of the predator's dash toward prey to add to the effect of the impact, and using wide jaw gapes as a way to keep the mandible out of the way of such blows. We re-interpret the evident adaptations for gape and for recruitment of neck muscles in head depression of Al/osaurus in terms of a muscle-powered bite directed at surfaces with moderate convexity, such as the bodies of very large preso In our model, the force s leading to penetration of the teeth are generated in the context of the opposition between the maxillary and the mandible. This interpretation allows us to incorporate all the observed adaptations of the Al/osaurus skull, while avoiding the problems created by previous models.[ES] La morfología craneal de Al/osaurus ha sido objeto de interpretaciones funcionales que implican un comportamiento depredador radicalmente distinto para el inferido para cualquier vertebrado depredador terrestre. Esas interpretaciones implican el uso de la dentición superior e inferior como análogos de cuchillos o dagas manufacturadas por el hombre, incorporando la inercia del golpe del depredador contra la presa para añadir el efecto del impacto, y usando amplias aperturas mandibulares para mantener la mandíbula fuera de la línea de acción del impacto. Reinterpretamos las evidentes adaptaciones para amplias aberturas mandibulares, y para la utilización de la musculatura cervical en la depresión de la cabeza de Allosaurus en función de una mordida basada en la fuerza muscular dirigida a superficies moderadamente convexas, como el cuerpo de una gran presa. En nuestro modelo, las fuerzas que producen la penetración son generadas en el contexto de una oposición entre el maxilar y la mandíbula. Esta interpretación nos permite incorporar todas las adaptaciones observadas en el cráneo de Allosaurus, al mismo tiempo que se evitan los problemas creados por modelos alternativos.Peer reviewe

The fossil vertebrates from Somosaguas (Pozuelo, Madrid, Spain)

[ES] Dos yacimientos de vertebrados, situados en el Campus de Somosaguas de la Universidad Complutense (Pozuelo de Alarcón, Madrid), han proporcionado unos 600 restos identificables en estados de conservación muy variados, pertenecientes a unas veinte especies de tamaños muy diversos, desde mastodontes a musarañas. Su estudio permite fechar su edad en unos 14 m.a. y reconstruir un periodo árido en la cuenca de Madrid, ocupada durante el Mioceno medio por bosques y sabanas subtropicales con fuertes avenidas y sin ríos permanentes. En estos yacimientos se puede realizar una enseñanza práctica de la Paleontología de Vertebrados, para formación de estudiantes universitarios en el estudio y la gestión del Patrimonio Paleontológico.[EN] Two vertebrate fossil sites, situated in the Universidad Complutense Campus of Somosaguas, (Pozuelo de Alarcón, Madrid, Spain) have yielded about 600 identifiable rests in different preservation states, belonging to about twenty species of highly diverse sizes, from mastodons to shrews. Their study allows dating at about 14 m.y., and reconstructing an arid climate epoch in the Madrid basin during middle Miocene times, occupied by subtropical woodlands and savannahs with strong floods and without permanent rivers. These fossil sites allow practical teaching of Vertebrate Palaeontology, and preparing university students in the Palaeontological Heritage study and management.Hemos recibido financiación y personal respaldo del Rectorado de la Universidad Complutense de Madrid, de los Decanatos de la Facultad de Ciencias Políticas y Sociología y de la Facultad de Ciencias Geológicas, y del Departamento de Paleontología de esta Facultad. El Departamento de Paleobiología del Museo Nacional de Ciencias Naturales (CSIC) realiza su investigación en el marco del Convenio de Colaboración con la Comunidad de Madrid a través de la Dirección General de Patrimonio Histórico Artístico de la Consejería de Educación.Peer reviewe

Actividades educativas en el yacimiento de vertebrados miócenos de Somosaguas (Universidad Complutense, Pozuelo de Alarcón, Madrid)

Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEpu

Los yacimientos de vertebrados continentales del Aragoniense superior (Mioceno medio) de Toril, Cuenca de Calatayud-Daroca

The paleontological sites of Toril 3A and B (Upper Aragonian, Biozone C3, MN 7/8) posses an exceptional and abundant fauna of vertebrates. From 1997 until 2001 these two localities have been object of systematic paleontological excavations. Up to now 36 species of large and small mammals have been found in these localities; the association of vertebrates also includes amphibians, reptiles and birds, among the remains of fossils birds it is frequent to found egg shell fragments. There are not significant differences in the qualitative and quantitative faunistic composition of the two sites; in both the undetermined bone fragments and the remains of chelonians, most of them dermal bones, are the dominant fossils. An important characteristic is the abundance of small size hornless ruminants, which are quite scarce in the stratified sites of the Spanish Aragonian. Neither there are differences in the composition of the micromammals, the association is overwhelmingly dominated (more than 95%) for different cricetid species; in Toril 3A beavers reappears for the first time during the Aragonian, and they will be frequent in younger faunas of the same basin. The fossils were deposited in different sedimentary environments, related with alluvial and shallow lacustrine environments

Measurement of the cosmic ray spectrum above 4×10184{\times}10^{18} eV using inclined events detected with the Pierre Auger Observatory

A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-\gamma}$ with index $\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV.Comment: Replaced with published version. Added journal reference and DO

Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory

The Auger Engineering Radio Array (AERA) is part of the Pierre Auger Observatory and is used to detect the radio emission of cosmic-ray air showers. These observations are compared to the data of the surface detector stations of the Observatory, which provide well-calibrated information on the cosmic-ray energies and arrival directions. The response of the radio stations in the 30 to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of the incoming electric field. For the latter, the energy deposit per area is determined from the radio pulses at each observer position and is interpolated using a two-dimensional function that takes into account signal asymmetries due to interference between the geomagnetic and charge-excess emission components. The spatial integral over the signal distribution gives a direct measurement of the energy transferred from the primary cosmic ray into radio emission in the AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air shower arriving perpendicularly to the geomagnetic field. This radiation energy -- corrected for geometrical effects -- is used as a cosmic-ray energy estimator. Performing an absolute energy calibration against the surface-detector information, we observe that this radio-energy estimator scales quadratically with the cosmic-ray energy as expected for coherent emission. We find an energy resolution of the radio reconstruction of 22% for the data set and 17% for a high-quality subset containing only events with at least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO

Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy

We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz. Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV arriving perpendicularly to a geomagnetic field of 0.24 G, scaling quadratically with the cosmic-ray energy. A comparison with predictions from state-of-the-art first-principle calculations shows agreement with our measurement. The radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers. Comparison with our result thus allows the direct calibration of any cosmic-ray radio detector against the well-established energy scale of the Pierre Auger Observatory.Comment: Replaced with published version. Added journal reference and DOI. Supplemental material in the ancillary file