M. Soledad Domingo

Late Neogene and Early Quaternary Paleoenvironmental and Paleoclimatic Conditions in Southwestern Europe: Isotopic Analyses on Mammalian Taxa

Climatic and environmental shifts have had profound impacts on faunal and floral assemblages globally since the end of the Miocene. We explore the regional expression of these fluctuations in southwestern Europe by constructing long-term records (from ∼11.1 to 0.8 Ma, late Miocene–middle Pleistocene) of carbon and oxygen isotope variations in tooth enamel of different large herbivorous mammals from Spain. Isotopic differences among taxa illuminate differences in ecological niches. The δ13C values (relative to VPDB, mean −10.3±1.1‰; range −13.0 to −7.4‰) are consistent with consumption of C3 vegetation; C4 plants did not contribute significantly to the diets of the selected taxa. When averaged by time interval to examine secular trends, δ13C values increase at ∼9.5 Ma (MN9–MN10), probably related to the Middle Vallesian Crisis when there was a replacement of vegetation adapted to more humid conditions by vegetation adapted to drier and more seasonal conditions, and resulting in the disappearance of forested mammalian fauna. The mean δ13C value drops significantly at ∼4.2−3.7 Ma (MN14–MN15) during the Pliocene Warm Period, which brought more humid conditions to Europe, and returns to higher δ13C values from ∼2.6 Ma onwards (MN16), most likely reflecting more arid conditions as a consequence of the onset of the Northern Hemisphere glaciation. The most notable feature in oxygen isotope records (and mean annual temperature reconstructed from these records) is a gradual drop between MN13 and the middle Pleistocene (∼6.3−0.8 Ma) most likely due to cooling associated with Northern Hemisphere glaciation.

NEW DATA ON THE MOSCHIDAE (MAMMALIA, RUMINANTIA) FROM THE UPPER MIOCENE OF SPAIN (MN 10- MN 11)

ABSTRACT New data on the last representatives of the Spanish Miocene Moschidae (Mammalia, Ruminantia) are presented and discussed. A new species of Micromeryx, Micromeryx soriae, is described on the basis of fossil material from the locality of La Roma-2 (upper Vallesian; MN 10, Teruel province, Spain, previously assigned to Micromeryx sp.), Batallones-1, and Batallones-10 (upper Vallesian; local zone J, MN 10, Madrid province, Spain). The new species is characterized by possessing relatively hypsodont lower molars of advanced morphology and a unique type of Palaeomeryx-fold. M. soriae gives insight to the last representatives of the genus, which achieved an overall lower molar morphology that mimics to certain degree that of Hispanomeryx. several characters of the upper molars of the Miocene moschids Micromeryx and Hispanomeryx are described that are useful for characterizing both genera. These characters are used to solve the taxonomic problems of PM-659, an upper molar from Puente Minero (MN 11, Teruel province, Spain) that represents one of the last survivors of the Moschidae in the Iberian Peninsula. The systematic utility of the upper molars of Hispanomeryx and Micromeryx is demonstrated, and the use of size as the only way to distinguish between the two genera is refuted. Finally, the study of the morphological characters of PM-659 clearly supports its generic change from Micromeryx sp. to Hispanomeryx sp., thus recording the presence of Hispanomeryx in the Iberian Peninsula as late as the lower Turolian.

Diversification of mammals from the Miocene of Spain

Abstract The mammalian fossil record of Spain is long and taxonomically well resolved, offering the most complete record of faunal change for the Neogene of Europe. We evaluated changes in diversification, composition, trophic structure, and size structure of large mammals over the middle and late Miocene with methods applied to this record for the first time, including ordination of fossil localities to improve temporal resolution and estimation of confidence intervals on taxa temporal ranges. By contrast, analysis within the traditional Mammal Neogene (MN) biochronology obscures important aspects of diversification. We used inferred temporal ranges of species and evaluated per capita rates of origination, extinction, diversification, and turnover over 0.5-Myr time intervals. Three periods of significant faunal change occurred between 12.0 and 5.5 Ma: (1) From 12.0 to 10.5 Ma, elevated origination rates led to an increase in diversity without significant change in ecological structure. Immigrants and geographic-range shifts of species to lower latitudes during an interval of global cooling contributed to these faunal changes. (2) From 9.5 to 7.5 Ma, high extinction rates followed by high origination rates coincided with significant changes in taxonomic composition and ecological structure. These changes represent the Vallesian Crisis, with replacement of a fauna of forest affinities (with frugivores and browsers) by a fauna of open woodlands (with grazers and mixed feeders). (3) From 6.5 to 5.5 Ma, high extinction rates reduced diversity without substantial changes in ecological structure, and large mammal faunas became highly endemic across the northern Mediterranean region. This interval includes the Messinian Salinity Crisis, the desiccation of the Mediterranean basin. Extinction may have been caused by geographic isolation and aridification, with evolution of endemic lineages giving rise to new species in the early Pliocene. These distinct macroevolutionary patterns of faunal change correspond to different geographic scales of inferred climatic and tectonic drivers.

Resource partitioning among top predators in a Miocene food web

The exceptional fossil sites of Cerro de los Batallones (Madrid Basin, Spain) contain abundant remains of Late Miocene mammals. From these fossil assemblages, we have inferred diet, resource partitioning and habitat of three sympatric carnivorous mammals based on stable isotopes. The carnivorans include three apex predators: two sabre-toothed cats (Felidae) and a bear dog (Amphicyonidae). Herbivore and carnivore carbon isotope (δ13C) values from tooth enamel imply the presence of a woodland ecosystem dominated by C3 plants. δ13C values and mixing-model analyses suggest that the two sabre-toothed cats, one the size of a leopard and the other the size of a tiger, consumed herbivores with similar δ13C values from a more wooded portion of the ecosystem. The two sabre-toothed cats probably hunted prey of different body sizes, and the smaller species could have used tree cover to avoid encounters with the larger felid. For the bear dog, δ13C values are higher and differ significantly from those of the sabre-toothed cats, suggesting a diet that includes prey from more open woodland. Coexistence of the sabre-toothed cats and the bear dog was likely facilitated by prey capture in different portions of the habitat. This study demonstrates the utility of stable isotope analysis for investigating the behaviour and ecology of members of past carnivoran guilds.

Origin of an assemblage massively dominated by carnivorans from the miocene of Spain.

Carnivoran-dominated fossil sites provide precious insights into the diversity and ecology of species rarely recovered in the fossil record. The lower level assemblage of Batallones-1 fossil site (Late Miocene; Madrid Basin, Spain) has yielded one of the most abundant and diversified carnivoran assemblage ever known from the Cenozoic record of mammals. A comprehensive taphonomic study is carried out here in order to constrain the concentration mode of this remarkable assemblage. Another distinctive feature of Batallones-1 is that the accumulation of carnivoran remains took place in the context of a geomorphological landform (cavity formation through a piping process) practically unknown in the generation of fossil sites. Two characteristics of the assemblage highly restrict the probable causes for the accumulation of the remains: (1) the overwhelming number of carnivorans individuals; and (2) the mortality profiles estimated for the four most abundant taxa do not correspond to the classic mortality types but rather were the consequence of the behavior of the taxa. This evidence together with other taphonomic data supports the hypothesis that carnivoran individuals actively entered the cavity searching for resources (food or water) and were unable to exit. The scarcity of herbivores implies that the shaft was well visible and avoided by these taxa. Fossil bones exhibit a very good preservation state as a consequence of their deposition in the restricted and protective environment of the chamber. Batallones-1 had another assemblage (upper level assemblage) that was dominated by herbivore remains and that potentially corresponded to the final stages of the cavity filling.

New insights on the taphonomy of the exceptional mammalian fossil sites of Cerro de los Batallones (late Miocene, Spain) based on rare earth element geochemistry

Abstract Cerro de los Batallones fossil sites are distinguished by large and diverse accumulations of Miocene vertebrate fauna. Little taphonomic research has been conducted on these assemblages so far, however. Results of Rare Earth Element (REE) analyses constrain diverse aspects of the taphonomic history undergone by the bones and constitute a starting point for subsequent taphonomic studies. Cerro de los Batallones localities were formed as cavities and seem to be composed of two types of assemblages that differ in their stratigraphic position, internal stratigraphic architecture, taxonomic composition and several taphonomic features. Despite these differences, chemically analyzed bones from the Batallones-1 upper and lower level assemblages exhibit undistinguishable REE patterns both within and between them. This, together with other taphonomic features, indicates that bones are autochthonous and that the depositional context remained constant during the sedimentation of the cavity filling. In addition, REE analyses are a key tool in unveiling the provenance of those fossil bones that could be regarded as allochthonous considering their peculiar macroscopic modifications. Negative Ce anomalies exhibited by isolated fossil bones lead to the proposal that the ponds that existed in the lower level of Batallones-1 were oxic. This inference clarifies the mode of accumulation of individuals in this assemblage: the carcasses did not accumulate massively over a brief period of time but rather they concentrated and, therefore, decayed over a relatively prolonged time span.

Mortality patterns and skeletal physical condition of the carnivorans from the Miocene assemblage of Batallones-1 (Madrid Basin, Spain)

This study was funded by the Spanish Government Ministry of Science and Innovation research projects CGL2008-05813-C02-01/BTE, CGL2007-60790/BTE, and CGL2010-19116/BOS and is included in the CAM-UCM 910607 Research Group. MSD was supported by the Fundacion Espanola para la Ciencia y la Tecnologia (FECYT) and the Spanish Ministry of Education Postdoctoral Fellowship Programme.