This paper presents the first complete estimate of the phylogenetic relationships among all 197 species of extant and recently extinct ruminants combining morphological, ethological and molecular information. The composite tree is derived by applying matrix representation using parsimony analysis to 164 previous partial estimates, and is remarkably well resolved, containing 159 nodes (> 80 % of the potential nodes in the completely resolved phylogeny). Bremer decay index has been used to indicate the degree of certainty associated with each clade. The ages of over 80% of the clades in the tree have been estimated from information in the literature. The supertree for Ruminantia illustrates which areas of ruminant phylogeny are still only roughly known because of taxa with controversial relationships (e.g. Odocoileini, Antilopinae) or not studied in great detail (e.g. Muntiacus). It supports the monophyly of the ruminant families and Pecora. According to this analysis Antilocapridae and Giraffidae constitute the superfamily Giraffoidea, which is the sister group of a clade clustering Bovoidea and Cervoidea. The position of several taxa whose systematic positions have remained controversial in the past (Saiga, Pelea, Aepycerus, Pantholops, Ammotragus, Pseudois) is unambiguously established. Nevertheless, the position of Neotragus and Oreotragus within the original radiation of the non-bovine bovids remains unresolved in the present analysis. It also shows that six successive rapid cladogenesis events occurred within the infraorder Pecora during the Oligocene to middle Pliocene, which coincided with periods of global climatic change. Finally, the presented supertree will be a useful framework for comparative and evolutionary biologists interested in studies involving the ruminants.

Global climate shifts and ecological flexibility are two major factors that may affect rates of speciation and extinction across clades. Here, we connect past climate to changes in diet and diversification dynamics of ruminant mammals. Using novel versions of Multi-State Speciation and Extinction models, we explore the most likely scenarios for evolutionary transitions among diets in this clade and ask whether ruminant lineages with different feeding styles (browsing, grazing and mixed feeding) underwent differential rates of diversification concomitant with global temperature change. The best model of trait change had transitions from browsers to grazers via mixed feeding, with appreciable rates of transition to and from grazing and mixed feeding. Diversification rates in mixed-feeder and grazer lineages tracked the palaeotemperature curve, exhibiting higher rates during the Miocene thermal maxima. The origination of facultative mixed diet and grazing states may have triggered two adaptive radiations-one during the Oligocene-Miocene transition and the other during Middle-to-Late Miocene. Our estimate of mixed diets for basal lineages of both bovids and cervids is congruent with fossil evidence, while the reconstruction of browser ancestors for some impoverished cladesGiraffidae and Tragulidae-is not. Our results offer model-based neontological support to previous palaeontological findings and fossil-based hypothesis highlighting the importance of dietary innovations-especially mixed feeding-in the success of ruminants during the Neogene.

Evolutionary theory has long proposed a connection between trait evolution and diversification rates. In this work, we used phylogenetic methods to evaluate the relationship of lineage-specific speciation rates and the mode of evolution of body size and tooth morphology in the Neogene and Quaternary radiation of horses (7 living and 131 extinct species). We show that diversification pulses are a recurrent feature of equid evolution but that these pulses are not correlated with rapid bursts in phenotypic evolution. Instead, rapid cladogenesis seems repeatedly associated with extrinsic factors that relaxed diversity bounds, such as increasing productivity and geographic dispersals into the Old World. This evidence suggests that diversity dynamics in Equinae were controlled mainly by ecological limits under diversity dependence rather than rapid ecomorphological differentiation.

The resource-use hypothesis predicts that generalist species have lower speciation and extinction rates than specialists. In this work we test several subsidiary predictions of the resource-use hypothesis using the biomic specialization index (BSI) for each African large mammal species, which is based on its geographical range within different climate zones. This index can be used globally allowing intercontinental and intertaxa comparisons. Our results are consistent with the axioms of the resource-use hypothesis theory, which predicts (1) a high frequency of stenobiomic species, (2) carnivores are more eurybiomic than herbivore clades (particularly, Artiodactyla and Primates), (3) the higher incidence of these biomic specialists in the tropical rainforest and desert biomes, and (4) the fact that certain combinations of inhabited biomes occur more frequently among species than do others. We also found that the tropical deciduous woodland is an important source of new species, and that there is a macroevolutionary segregation between extreme eurybiomic species (inhabitants of five or more biomes) and 'semi-eurybiomic' species (inhabitants of 2-5 biomes). These results can also be explained within the premises of the resource-use hypothesis. Finally, we discuss the relevance of our results to the understanding of the latitudinal gradient in species richness.

apparent head of Chasma Boreale was interpreted as an impact crater. Then, the Viking images showed the crater A detailed geomorphological study of Chasma Boreale, a did not exist, and other questions were raised over the widely known feature of Mars' north polar cap, has been carried out for the first time, along with a quantitative paleohydro-feasibility of the subglacial river.logical model. It is concluded that the chasma was eroded Clifford (1980Clifford ( , 1987 has studied in detail the mechaby a flow whose discharge was on the order of magnitude of nisms for a catastrophic water release from the permafrost, 109 m sec ؊1 . This catastrophic flow is thought to have been looking for analogs on both Earth and Mars. His comparipreceded by a powerful sapping process, caused by a tectoni-son with Ravi Vallis, a box-headed channel on Mars equacally focused thermal event. Several lines of evidence indicate tor (1ЊS, 43Њ) is particularly compelling, because of the tectonic control in the distribution and present aspect of most angular, straight head and huge flow marks. His hypothesis of the polar troughs. This tectonic forcing probably played a of glaciovolcanic outburst water flows (jö kulhlaups of Icemajor role in the inception of not only Chasma Boreale but landic authors) also seems appropriate, since this mechaalso other polar reentrants as well.

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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.

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