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.

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Venta Micena is an area containing several palaeontological sites marking the beginning of the Calabrian stage (Early Pleistocene). The richness of the fossil accumulation including species of Asian, African and European origin, makes Venta Micena a key site for the the palaeoecological and palaeoenvironmental study of southern Europe during the Early Pleistocene. Thus, research has been focused on Venta Micena 3, which was originally interpreted as a single palaeosurface associated with a marshy context, in which most of the fauna was accumulated by Pachycrocuta brevirostris. Recent excavations have unearthed a new site, Venta Micena 4, located in the same stratigraphic unit (Unit C) and in close proximity to Venta Micena 3. Here we show the first analyses regarding the taphonomic and spatial nature of this new site, defining two stratigraphic boundaries corresponding to two different depositional events. Furthermore, the taphonomic analyses of fossil remains seem to indicate a different accumulative agent than Pachycrocuta, thus adding more complexity to the palaeobiological interpretation of the Venta Micena area. These results contribute to the discussion of traditional interpretations made from Venta Micena 3.

Background: Specialised leaf-eating is almost universally regarded as the ancestral state of all ruminants, yet little evidence can be cited in support of this assumption, apart from the fact that all early ruminants had low crowned cheek teeth. Instead, recent years have seen the emergence evidence contradicting the conventional view that low tooth crowns always indicate leaf-eating and high tooth crowns grass-eating.

Key innovations are newly acquired structures that permit the performance of a new function and open new adaptive zones, and are, therefore, of paramount significance for understanding the history of the Ruminantia, particularly its diversification through the Miocene. Here we review and discuss what is known about these evolutionary novelties, with special emphasis on the appearance and evolution of cranial appendages and high-crowned (or hypsodont) teeth. Cranial appendages probably favored the diversification of pecorans by being structures strongly related to sexual selection, whereas the acquisition of hypsodont teeth could have expanded potential dietary breadth and allowed species to extend diets into the grazing range without eliminating browsing as a potential diet. When analyzed in conjunction with patterns of faunal diversity and in the context of climatic changes, it seems that the overall view that ruminant cranial appendages and hypsodonty may have started responding to increased patterns of seasonality and the opening-up of ecosystems is roughly valid. Instead, they occurred through several distinct pulses and varied widely among continents. This review is, to our knowledge, the first to highlight that the evolution of these innovations has been far from constant and uniform through time. Furthermore, we identify that both a first attempt to increase hypsodonty starting in the early Miocene and a first evolution of antlers and pronghorns were interrupted as a consequence of wide climatic fluctuations in the early-middle Miocene transition.

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From the latest Miocene to the Holocene period, three biotic events in the large mammal communities of the western Mediterranean region show significant and robust diversity changes and/or turnover with respect to sampling, and correspond in time to significant pulses of the latest Cenozoic glaciations. The 'Ruscinian mammal turnover pulse' represents a major biotic event close to the 'Messinian salinity crisis'. This can be described more as a turnover than a dispersion event. The pattern of turnover shows a significantly high value of first appearances close to the Mio-Pliocene transition; last appearances were also important but reduced significantly in the following interval. A Southern Hemisphere glaciation event has been related to the Messinian crisis. The second major biotic event corresponds to the so-called 'Equus-elephant event" during early Villafranchian time. The relevance of this dispersal event is proved by a marked increase in diversity as a result of a high number of first appearances. Between 3.0 and 2.6 Ma the onset of bi-polar glaciations occurred, followed by glacial interglacial cycles of moderate amplitude sustained at the orbital periodicity of 41 ka. The last major biotic event was the 'Galerian mammal turnover pulse' around 1.0 Ma. This turnover represents an important community reorganization that marks a total rejuvenation of the fauna and is coincident with the arrival of Homo species in the western Mediterranean region. At this time, glacial maxima became more extreme and the dominant periodicity of variation shifted to 100 ka, which is attributed to the massive Northern Hemisphere ice sheets.