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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. (C) 2017 Elsevier Ltd. All rights reserved.

Over the past five decades, fossil deposits within the Upper Burgi, KBS and Okote members at East Turkana in northern Kenya have provided many important insights into hominin behavior and ecology during a critical period in hominin evolution between 2.0 and 1.4 Ma. In this study, we use a large compilation of faunal abundance data from paleontological and archaeological collections at East Turkana dating to this time interval to investigate temporal patterns in large mammal taxa, ecosystem evolution and hominin ecology. Our analyses indicate that although portions of the ecosystem were dominated by mesic grasslands, the relative proportion of mesic and arid grassland environments varied though time. We document a major transition in the family Suidae with an increase in the abundance of fossils attributed to the Metridiochoerus lineage coeval with the local extinction of the Notochoerus lineage and decline in abundance of the Kolpochoerus lineage. Finally, by comparing the proportional representation of mammalian taxa found in paleontological collections versus those found in archaeological collections, our data suggest that archaeological sites at East Turkana, particularly those c.1.5 Ma, contain disproportionately large numbers of alcelaphin bovid remains. This could reflect 1) hominin prey choice, 2) hominin hunting/scavenging habitat choice, or 3) a combination the two.

The spatiotemporal pattern of the late Cenozoic spread of C 4 vegetation is an important indicator of environmental change that is intertwined with the uplift of the Himalaya and Tibetan Plateau, and the development of the East Asian monsoons. To explore the spread of C 4 vegetation in China and shed new light on regional climatic evolution, we measured δ 13 C values of more than 200 small mammal teeth (primarily rodents and lagomorphs) using a laser ablation isotope ratio mass spectrometry approach. Small mammals are highly sensitive indicators of their environment because they have limited spatial ranges and because they have minimal time-averaging of carbon isotope signatures of dietary components. The specimens originate from four classic Late Miocene fossil localities, Lufeng, Yuanmou, Lingtai, and Ertemte, along a southwest-northeast transect from Yunnan Province to Inner Mongolia. In Yunnan (Lufeng, Yuanmou) and on the Loess Plateau (Lingtai), the small mammal δ 13 C values record nearly pure C 3 ecosystems, and mixed but C 3 -based ecosystems, respectively, in agreement with previous studies based on carbon isotopes of large herbivores and soil carbonates. In Inner Mongolia, the micromammalian tooth enamel δ 13 C record picks up the presence of C 4 vegetation where large mammal samples do not, indicating a mixed yet C 3 -dominated ecosystem at ~ 6 Ma. As a whole, the results support a scenario of northward increasing C 4 grass abundance in a pattern that mirrors northward decreasing precipitation of the summer monsoon system. The results highlight differences between large and small mammals as indicators of C 4 vegetation in ancient ecosystems, particularly the ability of small mammal δ 13 C values to detect the presence of minor components of the vegetation structure.

The standard adaptive dynamics framework assumes two timescales, i.e. fast population dynamics and slow evolutionary dynamics. We further assume a third timescale, which is even slower than the evolutionary timescale. We call this the geological timescale and we assume that slow climatic change occurs within this timescale. We study the evolution of our model population over this very slow geological timescale with bifurcation plots of the standard adaptive dynamics framework. The bifurcation parameter being varied describes the abiotic environment that changes over the geological timescale. We construct evolutionary trees over the geological timescale and observe both gradual phenotypic evolution and punctuated branching events. We concur with the established notion that branching of a monomorphic population on an environmental gradient only happens when the gradient is not too shallow and not too steep. However, we show that evolution within the habitat can produce polymorphic populations that inhabit steep gradients. What is necessary is that the environmental gradient at some point in time is such that the initial branching of the monomorphic population can occur. We also find that phenotypes adapted to environments in the middle of the existing environmental range are more likely to branch than phenotypes adapted to extreme environments.

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 7 Ma) 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.

The East Asian climate history during the Neogene is a complicated and contentious issue, in particular because of its bearing on the development of the East Asian monsoon and Tibetan uplift chronology. Here we present a paleoprecipitation analysis based on mean molar tooth height (hypsodonty) of large herbivorous mammals to investigate the spatial pattern of climate zonation in East Asia during the middle Miocene. We show a generally humid and uniform situation before the late middle Miocene, replaced by a mid-latitude arid belt from the late middle Miocene, into the earlier part of the late Miocene. These findings are concordant with the global phenomena of the middle Miocene climate optimum and the subsequent cooling, and suggest that the predominant climate in East Asia for most of the Miocene was planetary rather than monsoonal. Our results support a late initiation of the East Asian summer monsoon, coincidentally with the beginning of eolian red clay deposition in the later late Miocene at 7–8 Ma.

Mammalian fossils, especially the Hipparion fauna, found in the Red Clay of the Loess Plateau, are of immense value for reconstructing late Neogene paleoecology and paleoclimatology in northern China. The lack of a precise chronological framework for these fossil sites has impeded our understanding of the evolution of the Chinese mammalian fauna, their correlation with European mammalian units, and the retrieval of paleoclimatic information. In this study, a field survey of regional stratigraphy in the Baode area of Shanxi was carried out and three profiles (Tanyugou, Yangjiagou-I and Yangjiagou-II) of Late Neogene deposits were selected for detailed investigation. A new chronological framework of the Late Neogene sequences in the Baode area is established by means of paleomagnetism. Our results show that the Red Clay accumulation in the Baode area began at least 7.23 Ma ago. Deposition continued to the superposed Jingle Formation. The most continuous and complete exposure of the Jingle Formation known to date was identified and dated to 2.72~5.34 Ma. A lithological distinction between the Jingle Formation and the underlying Baode Formation forms a clear boundary in the Red Clay that is not coincident with the Miocene/Pliocene boundary documented elsewhere. Three rich fossil layers are found in the Yangjiagou-II profile and dated to 6.43–6.54 Ma, 6.83–6.86 Ma and 7.15–7.18 Ma, respectively. With the application of three different demagnetization techniques, the Matuyama–Gauss geomagnetic reversal boundary was identified in a transitional unit between loess and typical Red Clay deposits. A lock-in depth of as large as 6.8 m (corresponding to ca. 65 ka) was inferred but remains unexplained.

The fossil teeth of land mammals offer a powerful tool to map the regional details of past climate change in the terrestrial realm. We use meanplant-eaterhypsodonty(molarcrownheight)oflateNeogenemammallocalitiestomaplateMioceneandPliocenepalaeoprecipitation on the Eurasian continent and, with higher temporal resolution, in Europe. The results show that the mid-latitude drying in Eurasia affected thecentral parts ofthecontinentfirst and thatthedrying of western Europeafter about7–8Maseemstohavecoincidedroughlyintimewith a return to more humid conditions in eastern Asia, with a return to a drier east and more humid west in the Pliocene. Within Europe, the hypsodonty-based palaeoprecipitation maps suggest that the sequence from MN 9 to MN 12 (ca. 11.1–6.8 Ma) was dominated by an east– west (continental-marine) humidity gradient, which gradually intensified and with a shift of dryer conditions eastwards in MN 12 (ca. 7.5Ma).ThiswaspartlyoverlainfromMN13onwardsbyanorth–southorientedgradient,whichpersistedatleasttotheendofthePliocene. The maps for both the earliest late Miocene (MN 9, ca. 11.1–9.7 Ma) and the earliest Pliocene (MN 14, ca. 4.9–4.2 Ma) show very low regional differentiation, possibly suggesting perturbed phases in the evolution of the mammal communities. Analysis of hypsodonty and dietary structure of the mammalian plant-eater community in Europe during the entire interval shows that the Miocene–Pliocene boundary was marked by a strong decrease in mesodont species and mixed feeders,and an increase in brachydont species and omnivores. In this view, the shift in the latest Miocene from east–west to partly north–south-polarised hypsodonty patterns corresponds mainly to an increase in hypsodont species and grazers. It seems probable that the east–west gradient was primarily driven by precipitation, while the north–south gradient would also have been strongly influenced by temperature-related effects of humidity.

Rhinocerotid remains from the middle Miocene Anatolian locality at Pasalar are described, and referred to Begertherium tekkayai, Aceratherium sp. aff. tetradactylum, and Brachypotherium brachypus. Begertherium tekkayai (= Beliajevina tekkayai HEISSIG) is only known from this locality. The material of Brachypotherium brachypus is similar to that from Sansan and Steinheim am Albuch (MN6–7), rather than to the earlier (informal) species B. stehlini known from La Romieu and Baigneaux (MN4), or to described African and Asian species. Begertherium tekkayai was probably a grazer, Aceratherium sp. a browser and Brachypotherium brachypus a mixed feeder. The very high proportion of juveniles in the Begertherium sample may point to accumulation by a predator.

The Pasalar fauna is found to include four suoid species including two listriodont pigs, Listriodon ef. splendens and Listriodon sp. nov., a tetraconodont, Conohyus simorrensis (sensu lato) and a peccary, Taucanamo inonuensis. This assemblage of folivores and “omnivores” presumably veflects the presence of relatively lush vegetation in the area. The cooccurrence of a derived sublophodont listriodont, Listriodon sp. nov., of roughly similar evolutionary grade to the late early Miocene European species Listriodon lockharti (from MN 4b and 5 localities of Europe) with the lophodont form Listriodon ef. splendens (MN 6-MN 9 localities of Europe suggests that the Pasalar fauna is referrable to MN 6, ea. 15 Ma, or possibly somewhat younger. While the Pasalar suoid assemblage shows broad Eurasian affinities, Listriodon sp. nov. and Taucanamo inonuensis provide evidence for a certain degree of endemism. We hypothesize here that this endemism developed after the late Burdigalian marine regression (ca. 17 Ma, and taken here as being chronologically equivalent to MN4b and lower MN 5), which promoted active Eurasian and African faunal exchanges.

A tubulidentate, a chalicothere and a hyracoid from Pasalar (middle Miocene of Western Anatolia) are described. The tubulidentate is referred to Orycteropus sp. The chalicothere is new to the site, and is referred to Chalicothere grande. Pliohyrax graecus was described from Pasalar by Hunermann 1985, based on material that probably does not come from this site. The new hyracoid remains are referred to Pliohyracidae incertae sedis. Coexistence of these forms might indicate a forest-woodland mosaic environment. There is no evidence of Tapirus from Pasalar ( contra Becker-Platen et al. [1975], Nagatoshi [1987]). Chalicotherium grande is a Western Eurasian element in the fauna, while the tubulidentate and the hyracoid apparently constitute the oldest records of these African forms outside Afroarabia. The presence of Chalicotherium grande suggest a maximum correlative age of MN5.