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How food intake and mastication scale to satisfy the metabolic needs of mammals has been the subject of considerable scientific debate. Existing theory suggests that the negative allometric scaling of metabolic rate with body mass is compensated by a matching allometric scaling of the chewing rate. Why empirical studies have found that the scaling coefficients of the chewing rate seem to be systematically smaller than expected from theory remains unknown. Here we explain this imparity by decoupling the functional surface area of teeth from overall surface area. The functional surface area is relatively reduced in forms emphasizing linear edges (e.g., lophodont) compared with forms lacking linear structures (e.g., bunodont). In forms with reduced relative functional surface, the deficit in food processed per chew appears to be compensated for by increased chewing rate, such that the metabolic requirements are met. This compensation accounts for the apparent difference between theoretically predicted and observed scaling of chewing rates. We suggest that this reflects adaptive functional evolution to plant foods with different fracture properties and extend the theory to incorporate differences in functional morphology. [ABSTRACT FROM AUTHOR]

Several large suid cranial remains attributed to Microstonyx major are part of a new Hipparion Fauna collection from the Hezheng area, Northern China. The new material confirms the presence of Microstonyx in the late Miocene of the area. The Chinese form belongs to a small-sized eastern population with reduced premolar row and clear sexual bimodality. Statistical comparison shows that Microstonyx major was a polymorphic species and reinforces recognition of Hippopotamodon as a separate genus, defined by relatively stout premolars resulting from a different underlying pattern of allometric growth. The presence of Microstonyx in North China and the distinct suid assemblage that lived there suggest biogeographic connections between Northern China and Western Eurasia in contrast to isolation from Southern China and the Indian subcontinent. The suid fauna of the late Miocene of Northern China seems to have been restricted to the later, more humid phase represented by the Red Clay faunas. [Copyright &y& Elsevier]

Venta Micena (Orce, Guadix-Baza Basin, Spain) is an Early Pleistocene locality renowned for the richness and quality of its palaeontological record. VM is spread over an area of 2.5 km2, where several exposed fossil outcrops are visible amidst its gorges and ravines. The best known of these sites, VM3, has been interpreted as a hyaena den. In addition, a new site, named VM4, has recently been the focus of fieldwork and taphonomic studies. The publication by Luzón et al. (2021) pointed out that VM4 presents a more complex history than VM3. First, two different sub-levels were identified: VM4-I and VM4-II. Secondly, the preliminary taphonomic analysis showed conspicuous differences with regard to VM3. Nevertheless, such interpretation has been challenged by Palmqvist et al. (2022) who proposed that VM3 and VM4 are both the result of a single depositional process, entailing the selective transport of skeletal parts by the giant extinct hyaena Pachycrocuta brevirostris back to its den. Using well-preserved faunal elements whose depositional context and provenance are reliable, in this paper we show that: 1) there are two clearly defined sub-levels in VM4 with some shared taphonomic characteristics as well as some notable differences; 2) VM3 and VM4 exhibit enough divergence to support differences in site formation processes; 3) The interpretation of both VM4-I and VM4-II is more consistent with their characterisation as open-air sites in which multiple agents and depositional processes contributed to its formation, rather than with hyaena dens. Nevertheless, excavations are still in progress at VM4 and therefore any results and interpretations ought to be considered as provisional. • VM3 has been interpreted as a hyaena den. • VM4 presents a more complex history than VM3. • VM4-II, is more consistent with an open-air site. • VM4 is not a carnivore den site. [ABSTRACT FROM AUTHOR]

Since the discovery of mammalian fossils in Central Inner Mongolia in the beginning of the 20th century, this area has produced a rich and diverse record of Miocene faunas. Nevertheless, the stratigraphy has remained poorly constrained owing to scattered faunal horizons and lack of continuous vertical exposures. Consequently, most age estimates of these Miocene sites are based on paleontological evidence alone, with very few sites having been dated independently. Our field investigations in Damiao, in Siziwang Qi, Inner Mongolia have yielded more than 30 new fossiliferous localities from three horizons, including a pliopithecid fauna. This study presents the litho-, bio- and magnetostratigraphy of the Damiao area and provides age estimates for the three fossil-bearing horizons. The sedimentary sequence is interpreted as the remains of a fluvial system comprising channels, subaerially exposed floodplains and floodbasin environments. The two local stratigraphic sections measured and sampled for paleomagnetic analysis coincide with species-rich vertebrate fossil localities. The paleomagnetic results and faunal evidence suggest a correlation of lowermost fossil horizon (DM16) producing relatively rich small mammal assemblage to the early Miocene chron C6Ar or C6An.1r, roughly in 20–21 Ma age range. The pliopithecid locality level (DM01) represents latest middle Miocene and has an age estimate of about 12.1 Ma while the youngest localities (DM02) with cervoids and abundant and diverse small mammal fauna represents the earliest late Miocene with an age estimate of about 11.6 Ma. Our magnetostratigraphic results confirm that the Damiao strata constitute one of the best sequences in Inner Mongolia with early, middle and late Miocene mammalian faunas in stratigraphic superposition. The results also provide constraints on the paleoenvironmental evolution and bioevents of the area. The occurrence of pliopithecid primates in the middle Miocene of Inner Mongolia suggests humid habitats and challenges the scenarios suggesting arid and highly seasonal conditions for Central Asia since Early Miocene. The presence of pliopithecids may also bear witness to locally humid environments and greater habitat heterogeneity than previously known in central Inner Mongolia. [ABSTRACT FROM AUTHOR]

Abstract: The fossil record for the Late Miocene indicates that high latitudes were warmer than today and that the equator-to-pole temperature gradient was weak. Experiments with climate models have not been sufficiently able to represent warm polar conditions for the Late Miocene. This demonstrates that our explanation of warm high latitudes in the Late Miocene is not complete. In addition, heat transport mechanisms have not been so frequently addressed to understand the differences between the Late Miocene and modern climate. Here we present a model simulation for the Tortonian (11 to 7Ma) using a complex fully-coupled atmosphere–ocean general circulation model to address heat transport mechanisms relative to modern conditions. Because of an open Central American Isthmus, the zonal mean northward ocean heat transport in the Northern Hemisphere generally decreases in our Tortonian run. As a consequence, the northward atmospheric heat transport is stronger in the Tortonian experiment. In northern mid-latitudes, the sensible and latent heat fluxes related to transient eddies increase compared to today. The stronger poleward transient eddy heat transport in the Tortonian model run correlates with intensified stormtracks in the mid-latitudes. In the palaeoclimate model run, the increased northward transient eddy heat transport together with the different-than-present land surface cover leads to a warming of polar regions and, hence, to a reduction of the meridional temperature gradient. The low elevation of Tibet in our palaeoclimate experiment causes a general weakening of the monsoon system in Asia. The E-Asian monsoon precipitation decreases compared to our reference run, but monsoon rainfall in India increases. When comparing the model results with quantitative terrestrial proxy data, we observe some discrepancies for some specific localities. However, the large patterns in our Tortonian run agree fairly well with the fossil record. [Copyright &y& Elsevier]

Nearly five decades ago Berggren and Van Couvering proposed an Old World " Hipparion Datum" wherein a North American Hipparion extended its range across Eurasia and Africa as an "instantaneous prochoresis" populating the Old World. Four decades ago Woodburne and Bernor examined European and North African hipparion assemblages and proposed a number of distinct hipparion lineages, sharply departing from the mono-generic paradigm of previous work. Through the 1980s until now, hipparion systematic studies have delineated multiple superspecific groups of hipparions. Herein, we define 10 recognizable genus-rank Eurasian and African taxa delineating their chronologic occurrences, geographic extent and where data exists, their body mass and paleodietary preferences. Our study supports the current interpretation that a species of North American Cormohipparion extended its range into the Old World in the early late Miocene. Regional first occurrences of Cormohipparion are recognized in the Potwar Plateau, Pakistan and Sinap Tepe, Turkey 10.8 Ma. The slightly derived lineage Hippotherium is recorded earlier in the Pannonian C of the Vienna Basin, 11.4–11.0 Ma marking the chronologic "Hipparion" Datum at the lower boundary of Mammal Neogene (MN) Unit 9. Within MN 9, 11.2–9.9 Ma, Cormohipparion underwent a minor diversification whereas Hippotherium diversified in Central and Western Europe and China and Sivalhippus (S. nagriensis) originated in the Indian Subcontinent. Whereas Cormohipparion did not survive into the late Vallesian, MN10 (9.9–8.9 Ma), Hippotherium and Sivalhippus did and the Cremohipparion and Hipparion s.s. lineages originated. During the early and middle Turolian (MN11–12, 8.9–6.8 Ma) Hippotherium, Sivalhippus, Cremohipparion and Hipparion persisted and new lineages, Eurygnathohippus, Plesiohipparion, Baryhipparion and Shanxihippus originated. An initial extinction interval occurred at the end of the Miocene, MN13 (6.8–5.3 Ma) wherein all but one endemic species of Hippotherium, H. malpassi (Italy), Hipparion and several species of Cremohipparion became extinct. Lineage and species reduction continued across the Mio-Pliocene boundary so that by the beginning of the Pliocene (MN14, 5.3 Ma) only African species of Eurygnathohippus, Chinese Plesiohipparion houfenense and Proboscidipparion sinense remained. The later Pliocene (MN15–16, ca. 5.0–2.5 Ma) documents the persistence of endemic Chinese Baryhipparion insperatum , modest diversification of African Eurygnatohippus spp. and Chinese Plesiohipparion and Proboscidipparion spp. Eurygnathohippus made a limited geographic extension into the Indian subcontinent during MN16, whereas Pleisohipparion and Proboscidipparion extended their ranges into Eurasia during MN15 and MN16. The latest occurring hipparions are Proboscidipparion sinense at 1.0 Ma in China and Eurygnathohippus cornelianus in Africa <1.0 Ma. Old World hipparion lineages early on increased their body mass in MN9. During the Turolian interval (MN11–13) hipparion lineages diversified their body mass from very small (<100 kg) to heavy forms (>300 kg), with the smaller forms being predominately grass feeders and larger ones being mixed feeders. Decreased hipparion lineage and species diversity in the Pliocene was accompanied by increased average body size and hypsodonty probably in response to more seasonal Eurasian and African environments. There is no evidence that hipparions ever adapted to cold and dry Old World Pleistocene environments. • Overview of Old World hipparion evolution and ecology after the Hipparion Datum • Integrated paleobiogeography, dietary and body size trends of Old World hipparions • Molar crownheight of hipparion occurrences mapped on regional paleoclimate over time [ABSTRACT FROM AUTHOR]

The Guadix-Baza Basin (GBB) in Andalucía, Spain, comprises palaeontological and archaeological sites dating from the Early Pliocene to the Middle Pleistocene, including some of the earliest sites with evidence for the presence of early humans (Homo sp.) in Europe. Thus, the history of climate and environments in this basin contributes significantly to our understanding of the conditions under which early humans spread into Europe during the Early Pleistocene. Here we present estimates of precipitation and primary productivity in the GBB from the Pliocene to the Middle Pleistocene based on dental ecometrics in fossil communities of large herbivorous mammals, and perform an ecometrics-based distribution modelling to analyse the environmental conditions of Early and Middle Pleistocene human sites in Europe. Our results show that Early Pleistocene humans generally occupied on average relatively diverse habitats with ecotones, such as woodlands and savannas, but avoided very open and harsh (cool or dry) environments. During the Middle Pleistocene in Europe, humans occupied a comparatively much broader range of environments than during the Early Pleistocene, but were on average more concentrated in environments where the dental ecometric of mammals indicate wooded palaeoenvironments. In the earliest human occupation sites of the GBB, Barranco León and Fuente Nueva 3, the mean annual precipitation and net primary production estimates indicate climatic conditions close to modern Mediterranean sclerophyllous woodland environments, but with slightly higher primary productivity, indicating some similarity with East African woodlands. On the other hand, the environments did not resemble African grassland savannas. The browse-dominated diets of ungulates from Barranco León and Fuente Nueva 3 further suggest palaeoenvironments where grasses were a minor component of the vegetation. In the slightly older site of Venta Micena that has no evidence for the presence of hominins, dental ecometric estimates indicate climate and environments similar to Mediterranean "forest steppe" environments existing in the surroundings of Baza today. Grasses were prevalent in the diet of some taxa, especially equids, in Venta Micena, but most of the species show browse-dominated diets even there. • Plio-Pleistocene climate history of the Guadix-Baza Basin was reconstructed based on large mammal dental ecometrics. • The climate during the Pleistocene ranged from that of the modern Mediterranean to slightly more humid and productive. • Environments in the Guadix-Baza Basin during the Pleistocene were mostly Mediterranean woodlands and shrublands. • There were hardly any grazers among the ungulates of the three Orce sites studied, suggesting grass-poor paleoenvironments. • Early humans dispersed in Europe during the Early Pleistocene in climatically mild environments, avoiding harsh conditions. [ABSTRACT FROM AUTHOR]

The Early Pleistocene sites of Barranco León and Fuente Nueva 3 (Guadix-Baza Basin, SE Spain) have yielded abundant Oldowan lithic artifacts and one hominin tooth (Homo sp. in level D1 or D2 of Barranco León), today considered to be among the earliest evidence for a hominin presence in Western Europe, at ca. 1.4–1.2 Ma. Here, for the first time, the stratigraphic succession of these two sites are studied more precisely from a palaeoenvironmental point of view, taking into account the different levels of the depositional sequences to analyze the successive fossil assemblages of amphibians and reptiles. Palaeoenvironmental reconstructions are carried out by applying the "habitat weighting" method, which uses the modern distribution by habitat of amphibian and reptile species in order to interpret past landscapes. The successive herpetofaunal assemblages from Barranco León show a certain tendency towards more arid conditions from level D1 to level E, whereas in Fuente Nueva 3 environmental reconstructions reveal oscillating conditions, with a tendency towards more arid conditions in the basal part of the sequence, up to level 5, where the tendency shifts back to more humid conditions. Our results show that the layers included in this study with the highest density of anthropic evidence (such as level 5 in FN 3 and levels D1 and D2 in BL) are situated within the late Early Pleistocene climatic and environmental cyclicity, yielding different environmental conditions: a humid, wooded biotope for BL, and a more open and drier biotope in FN 3. This suggests that the hominins of the late Early Pleistocene, although conditioned to some extent by climatic factors, were able to cope with changing environmental conditions, both "interglacial" and "glacial", in the southwestern extremity of the European continent. • Amphibians and reptiles are good proxies for the environmental reconstructions. • Paleoenvironmental conditions are reconstructed by stratigraphic levels. • The first hominins in Western Europe coped with changing environmental conditions. • The paleoenvironmental changes are in agreement with the climate oscillations. [ABSTRACT FROM AUTHOR]