Comunicación presentada en el XIII Encuentro en Jóvenes Investigadores en Paleontología (XIII EJIP) - 
 XIII Meeting of Early-Stage Researchers in Paleontology (XIII EJIP): Cercedilla, 15 - 18 de Abril de 2015Peer reviewe

Abella, Juan

Domingo, Laura

Domingo, M. Soledad

Morales, Jorge

Valenciano, Alberto

Digital.CSIC

85XIII EJIP Conference ProceedingsKeywords: carbon stable isotopes, Madrid Basin, Cerro de los Batallones, carnivores, Bayesian mixing-modelPalabras clave: isótopos estables del carbono, Cuenca de Madrid, Cerro de los Batallones, carnívoros, modelos de mezcla bayesianos1Departamento de Paleontología, Facultad Ciencias Geológicas, UniversidadComplutense de Madrid, C/ José Antonio Novais 12, 28040, Madrid, Spain. *E-mail: soldomingo@gmail.com2Departamento de Geología Sedimentaria y Cambio Medioambiental, Instituto de Geociencias IGEO-CSIC-UCM, C/ José Antonio Novais 12, 28040, Madrid, Spain.3Earth and Planetary Sciences Department, University of California Santa Cruz, 1156 High Street, Santa Cruz, California 95064, U.S.A.4Instituto de Investigación Científica y Desarrollo tecnológico (INCYT-UPSE), Universidad Estatal Península de Santa Elena, Avda. Principal La Libertad, 240210, Santa Elena, Ecuador.5Institut Català de Paleontologia Miquel Crusafont, Campus Universitat Autònoma de Barcelona, 08193, Cerdanyola del Vallès, Barcelona, Spain.6Departamento de Paleobiología, Museo Nacional de Ciencias Naturales-CSIC, C/ José Gutiérrez Abascal 2, 28006, Madrid, Spain.M. Soledad Domingo1*, Laura Domingo1, 2, 3, Juan Abella4, 5, Alberto Valenciano1, 2 y Jorge Morales6Paleoecología de mamíferos carnívoros de los yacimientos miocenos de Batallones-1 y Batallones-3 (Cuenca de Madrid, España) a través de isótopos estables del carbonoCarbon stable isotope paleoecology of carnivorans from the Miocene localities of Batallones-1 and Batallones-3 (Madrid Basin, Spain)Sites dominated by carnivoran remains are rare in the fossil record because mammalian fossil assemblages normally reflect the herbivore:carnivoran proportion of living communities, which has been estimated as 10:1 (Eisenberg 1981). These sites are usually formed under exceptional taphonomic circumstances and constitute unique opportunities to study diverse aspects of past carnivoran guilds, from taxonomic diversity to ecomorphological traits to trophic interactions. Stable isotope analysis on dental enamel is a proven robust method to make inferences on the diet and resource and habitat use of extinct mammals.In Cerro de los Batallones Miocene paleontological complex (Madrid Basin, Spain), two sites, Batallones-1 (BAT-1) and Batallones-3 (BAT-3), are primarily composed of carnivoran remains (> 97% of the large-mammal remains; Table 1) and are providing precious information about taxa that were previously unknown or poorly known in the fossil record of mammals. In the Late Miocene, these sites acted as natural traps for the fauna. The two sites are diverse in their carnivoran faunal composition with BAT-1 recording a total of 10 species and BAT-3 recording a total of 13 species. Although BAT-1 and BAT-3 are dated as Vallesian (ca. 10-9 Ma), it seems that BAT-3 is slightly younger than BAT-1 (based on small-mammal biochronology) and differences in their carnivoran compositions have been attributed to these temporal difference. An associated environmental shift has been proposed as a probable cause behind these taxonomic and abundance differences but it remains unclear.In a previous study, we conducted carbon stable isotope analyses on three sympatric hypercarnivores from BAT-1: the sabertoothed cats Promegantereon ogygia and Machairodus aphanistus, and the amphicyonid Magericyon anceps (Domingo et al. 2013). In this paper, we expand the isotopic sampling to BAT-3 carnivorans (including Promegantereon ogygia, Machairodus aphanistus and Magericyon anceps, but also the ursid Indarctos arctoides, the giant mustelid Eomellivora piveteaui and the amphicyonid Thaumastocyon sp.) in order to compare the feeding ecology of BAT-1 and BAT-3 carnivore populations and to evaluate a possible environmental change between these two sites.For mammals, the carbon stable isotope composition (δ13C) of tooth enamel tracks primarily the δ13C values of their diet (Koch 2007). δ13C values of herbivorous mammals reflect the values of ingested plants, which varies depending on plant photosynthetic pathways (C3, C4, CAM) as well as on ecological factors (e.g., aridity, canopy density) that affect fractionation during photosynthesis. δ13C values of carnivore mammals reflect the values of ingested prey (Koch 2007). By extension, δ13C values yielded by mammalian fossil enamel are a reliable tool for reconstructing the type(s) of habitats where the animals lived.We sampled and analyzed the enamel of 63 carnivoran teeth. Twenty seven teeth belonged to BAT-1 carnivores. The remaining 36 teeth belonged to BAT-3 carnivores. The twenty six herbivore tooth samples analyzed in this study correspond to hipparionine horses (Family Equidae, Hipparion sp.), a pig (family Suidae, Microstonyx sp.), an antelope (Family Bovidae, Austroportax sp.) and another bovid that is under study (Bovidae indet.). Teeth analyzed in this work were all from adult individuals and are housed in the collections of the Museo Nacional de Ciencias Naturales-CSIC (Madrid, Spain). XRD Current Trends in Paleontology and Evolution86Rather, the differences in the taxonomic composition and remain abundances (Table 1) between BAT-1 and BAT-3 could be a reflection of the real carnivoran population densities and of the pattern of entrance and exit of carnivoran species from the Madrid Basin that would be driven by carnivore interactions (e.g., competitive displacement) rather than by a shift in the habitat.The Bayesian mixing model allowed us to characterize the contribution of selected prey to the carnivoran diet. In the case of the two sabertoothed cats, we have detected subtle changes in their prey preferences, with BAT-1 populations preferring to take the undetermined Bovidae and BAT-3 populations preferring the hipparionine horses. The considerable amount of medium to large predator species in BAT-3 with hypercarnivore diets along with the high overlap in their δ13C values and similar δ13C variances implying the occupation and use of a similar portion of the habitat are indicative of a strong interspecific competition among them (stronger than in BAT-1). The Bayesian mixing model also points to high levels of rivalry among BAT-3 predators as it resulted into a common preferred prey for BAT-3 carnivores: Hipparion sp. Both in BAT-1 and BAT-3, the exception seems to be the amphicyonid Magericyon anceps, whose δ13C values imply resource partitioning with the use of prey from a more open portion of the woodland-mesic C3 grassland habitat compared to the rest of carnivorans.was performed on a subset of Cerro de los Batallones teeth to control for diagenetic changes. All the teeth analyzed yielded a hydroxyapatite mineralogy, demonstrating that they preserved the original mineral composition. We followed the protocol of Koch et al. (1997) for enamel pretreatment. Carbon stable isotope results are reported in δ-notation, δHXsample=[(Rsample–Rstandard)/ Rstandard]×1000, where X is the element, H is the mass of the rare, heavy isotope, and R=13C/12C. The isotopic reference standard for carbon is Vienna Pee Dee Belemnite (VPDB). We contrasted δ13C values of BAT-1 and BAT-3 using Student’s t-tests, analysis of the variance (ANOVA) and post-hoc Tukey tests. We used MixSIAR (Stock and Semmens 2013), a Bayesian mixing model, to estimate the proportions of prey contributions to the diet of each predator based on their δ13C values.All the statistical comparisons carried out on the δ13C values, i.e., BAT-1 vs BAT-3 entire carnivore faunas, BAT-1 vs BAT-3 Promegantereon ogygia,  BAT-1 vs BAT-3 Machairodus aphanistus, and BAT-1 vs BAT-3 Hipparion sp., demonstrate that the habitat remained stable (i.e., there are no statistical differences in the δ13C values) in the time elapsed between BAT-1 and BAT-3 with the predominance of a woodland-mesic C3 grassland habitat. Then, changes observed in the carnivoran composition and proportions of remains do not seem to be the consequence of a shift in the environmental conditions occurred over the time between the formation of BAT-1 and BAT-3. Taxon Family/Order Batallones-1Batallones-3NISP % NISP %Promegantereon ogygia* Felidae/Carnivora 7125 49.53 3116 29.33Machairodus aphanistus* Felidae/Carnivora 3226 22.43 3869 36.42Amphicyonidae* Amphicyonidae/Carnivora 858 5.96 525 4.94Indarctos arctoides* Ursidae/Carnivora - 1984 18.68Eomellivora piveteaui* Mustelidae/Carnivora - 251 2.36Protictitherium crassum Hyaenidae/Carnivora 1339 9.31 418Simocyon batalleri Ailuridae/Carnivora 178 1.24 -Felinae Felidae/Carnivora 775 5.39 142 1.34Mustelidae/Mephitidae Mustelidae-Mephitidae/Carnivora 453 3.15 266 2.50Hipparion sp.* Equidae/Perissodactyla 30 0.21 18 0.17Rhinocerotidae Rhinocerotidae/Perissodactyla 273 1.90 6 0.06Moschidae Moschidae/Artiodactyla 56 0.39 5 0.05Suidae* Suidae/Artiodactyla 67 0.47 5 0.05Bovidae* Bovidae/Artiodactyla 5 0.03 18 0.17Total Carnivora 13954 97.00 10571 99.51Total Perissodactyla 303 2.11 24 0.23  Total Artiodactyla 128 0.89 28Table 1. Abundances and proportions of large-mammals from Batallones-1 and Batallones-3. NISP = Number of Identified Specimens. Undetermined remains are excluded from this table. Taxa analyzed in this study are marked with an asterisk. In Batallones-1, Amphicyonidae is exclusively represented by Magericyon anceps. In Batallones-3, Amphicyonidae is represented by Magericyon anceps and Thaumastocyon sp. Several species are included within Felinae, Mustelidae/Mephitidae, Rhinocerotidae, Moschidae and Bovidae.87XIII EJIP Conference ProceedingsReferencesEisenberg J (1981) The Mammalian Radiations. The University of Chicago Press, Chicago, 610 pp.Domingo MS, Domingo L, Badgley C, Sanisidro O, Morales J (2013) Resource partitioning among top predators in a Miocene food web. Proceedings of the Royal Society B, 280: 20122138. Koch P (2007) Isotopic study of the biology of modern and fossil vertebrates, in  Michener R, Lajtha K (Eds.), Stable Isotopes in Ecology and Environmental Science. Blackwell, Boston, 99-154 pp. Koch PL, Tuross N and Fogel ML (1997) The effects of sample treatment and diagenesis on the isotopic integrity of carbonate in biogenic hydroxylapatite. Journal of Archaeological Science, 24: 417-429. Stock BC and Semmens BX (2013) MixSIAR GUI User Manual, version 1.0. http://conserver.iugo-cafe.org/user/brice.semmens/MixSIAR (accessed October 2014).

Paleoecología de mamíferos carnívoros de los yacimientos miocenos de Batallones-1 y Batallones-3 (Cuenca de Madrid, España) a través de isótopos estables del carbono

Paleoecología de mamíferos carnívoros de los yacimientos miocenos de Batallones-1 y Batallones-3 (Cuenca de Madrid, España) a través de isótopos estables del carbono

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