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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 Luz on 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., Consejeía de Cultura de la Junta de Andalucia through the General Research Project Primeras ocupaciones humanas y contexto paleoecologico a partir de los depositos Plio-pleistocenos de la cuenca Guadix-Baza BC.03.032/17, Inside the Artefacts & Ecofacts" Excellence Unit (University of Granada) HUM-607 PID 2021.125098NB.I00 MCIN/AEI/10.13039/501100011033/FEDER, Una manera de hacer Europa ProyExcel_00274 2021 SGR 01238, Agencia de Gestio D'Ajuts Universitaris de Recerca Agaur (AGAUR) Generalitat de Catalunya, National Health and Medical Research Council (NHMRC) of Australia PRE2020-094482 CEX2019-000945-M-20-1, Spanish Government, Archaeometrical Studies. Inside the Artefacts & Ecofacts" Excellence Unit (University of Granada

We know that the fossil record is incomplete. But how incomplete? Here we very coarsely estimate the completeness of the mammalian record in the Miocene, assuming that the duration of a mammalian species is about 1 Myr and the species diversity has stayed constant and is structurally comparable to the taxonomic diversity today. The overall completeness under these assumptions appears to be around 4%, but there are large differences across taxonomic groups. We find that the fossil record of proboscideans and perissodactyls as we know it for the Miocene must be close to complete, while we might know less than 15% of the species of artiodactyl or carnivore fossil species and only about 1% of primate species of the Miocene. The record of small mammals appears much less complete than that of large mammals.

The Red Queen's hypothesis portrays evolution as a never-ending competition for expansive energy, where one species’ gain is another species’ loss. The Red Queen is neutral with respect to body size, implying that neither small nor large species have a universal competitive advantage. Here we ask whether, and if so how, the Red Queen's hypothesis really can accommodate differences in body size. The maximum population growth in ecology clearly depends on body size—the smaller the species, the shorter the generation length, and the faster it can expand given sufficient opportunity. On the other hand, large species are more efficient in energy use due to metabolic scaling and can maintain more biomass with the same energy. The advantage of shorter generation makes a wide range of body sizes competitive, yet large species do not take over. We analytically show that individuals consume energy and reproduce in physiological time, but need to compete for energy in real time. The Red Queen, through adaptive evolution of populations, balances the pressures of real and physiological time. Modeling competition for energy as a proportional prize contest from economics, we further show that Red Queen's zero-sum game can generate unimodal hat-like patterns of species rise and decline that can be neutral in relation to body size.

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 Leon 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 Leon 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.

The writings of Gottfried Wilhelm Leibniz (1646–1716) provide a window on early evolutionary thinking of a kind interestingly different from the roots of modern evolutionary theory as it emerged in the years following the French Revolution. Here we relate aspects of Leibniz’s thinking to methods of modern palaeoecology and show that, despite a different terminology and a different hierarchic focus, Leibniz emerges as a strikingly modern theoretician, who viewed the living world as dynamic and capable of adaptive change. The coexistence approach of palaeoecological reconstruction, developed by Volker Mosbrugger and collaborators, with its core assumption of harmoniously co-adapted communities with strong historical legacy, represents, in a positive sense, a more Leibnizian view than functionally based and theoretically history-free approaches, such as ecometrics. Recalling Leibniz’s thinking helps to highlight how palaeoecological reconstruction is about much more than reliably establishing the ecological and climatic situation of a given fossil locality. While reliable reconstructions of past conditions are certainly of great value in research, it is arguably the need to think deeply about how the living world really works that keeps palaeoecological reconstruction such a long-running and central aspect of evolutionary science. And while we struggle to understand the coexistence and dynamic interaction of endless levels of living agents of the living world, simultaneously large and small, global and local, the coexistence approach of palaeoecological reconstruction remains both an outstandingly operational method and part of a philosophical tradition reaching back to the very earliest evolutionary thinking.

The Early Pleistocene sites of Barranco Leon 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 Leon), 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 Leon 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. (C) 2020 Elsevier Ltd. All rights reserved.

A new study by Fraser et al (2018) urges the use of phylogenetic comparative methods, whenever possible, in analyses of mammalian tooth wear. We are concerned about this for two reasons. First, this recommendation may mislead the research community into thinking that phylogenetic signal is an artifact of some sort rather than a fundamental outcome of the evolutionary process. Secondly, this recommendation may set a precedent for editors and reviewers to enforce phylogenetic adjustment where it may unnecessarily weaken or even directionally alter the results, shifting the emphasis of analysis from common patterns manifested by large clades to rare cases.

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.

After a long period of inactivity, recent excavations at the late Miocene Maragheh Formation unexpectedly resulted in the discovery of the first fossil hominoid and second Mesopithecus remains from this area. The discovery motivated a new international initiative to conduct research in these rich fossil sites. These studies focused on the fossil hominoid and its locality, aiming to reveal more about the context of this fossil discovery. Detailed stratigraphy, sedimentology and magnetostratigraphy studies were conducted. New samples from volcaniclastic key horizons (pumice beds) in Dareh Gorg, where the hominoid fossil site is located, were dated by radiometric methods. The radiometric age determinations provide a firm tie-point for the geochronology. The polarity pattern in the palaeomagnetically investigated section corroborates the K-Ar results. The preliminary magnetostratigraphic results suggest that the hominoid locality can be correlated to the normal polarity chron C4n.2n (8.108–7.695 Ma), C4n.1n (7.642–7.528 Ma) or C3Br.1n (7.285–7.251 Ma), placing it at intervals corresponding to the mammal units MN11 or possibly early MN12. The study of fossil hominoid indicates broad affinities with a number of contemporaneous taxa from the Balkan-Iranian palaeoprovince, as well as Siwaliks and southeast Asia. A preliminary analysis of the accompanying (in situ) fauna at the hominoid site indicates the highest similarity of this level to Turolian hominoid- and Mesopithecus-bearing localities in Turkey, Greece and Bulgaria. However, some environmental differences are observed among these localities, based on their faunal structure and taxon properties, as well as in the different masticatory adaptations of their hominoids.

The Maragheh Formation is an important deposit, which yields the savanna-type large mammal assemblage known as the “Pikermian Fauna.” Our high-resolution facies analysis of the interval between the Lower Pumice and the White Tuff demonstrated that debris-flow deposits and paleosols are dominant in the studied sequence. Fluvial channel-fill and small pond facies are the subordinate components in this interval. Most of the channel-fill deposits are interpreted as having been accumulated from ephemeral streams. The wide distribution of the Middle Pumice, the fact that it contains grains with older ages than those of the Lower Pumice, and the presence of “traction carpet” deposits allow the interpretation of the pumice interval as having been deposited from a hyperconcentrated flow probably caused by crater-lake destruction around the peak of Mt. Sahand, which supplied older rocks to the flow. The internal architecture of fluvial channel-fill deposits and the structures of paleosols (rhizoliths, cracks and slickensides: probable Vertic Inceptisols) imply a seasonal climate during deposition of the studied interval. This is consistent with previous environmental reconstructions based on mammal fossils (woodland-dominated savannah) as well as the results of phytolith analysis and δ18O data obtained from northern Iran. However, flood deposits covering the paleosols, showing sheet-like geometry, may not have been affected by large trees on the flood plain: the extent of woodland around the study site appears to have been limited.

Maragheh in northwestern of Iran is a world famous Miocene fossil-bearing area. The area has yielded classical late Miocene Turolian age fauna that has been collected and studied sporadically over the last 150 years. However, the precise correlation of these sediments to the Global Time Scale (GTS) has remained ambiguous. To address this, 115 levels along an approximately 27-m-thick interval were collected from the middle Maragheh Formation at Dareh Gorg (Gort Daresi) section. Characteristic remanent magnetization directions obtained by alternating field demagnetization produce a polarity pattern that is supported by thermal demagnetization on a set of sister specimens. Three polarity intervals were recognised, the middle part of the section at around 15-21 m showing reversed polarity, bounded by normal polarities above and below. Based on the palaeontological constraints and recent K-Ar age determinations from the Maragheh Fm, three correlations to the geomagnetic polarity time scale appear likely. According to these correlations, recently discovered hominoid locality is correlated to C3Br.1n, C4n.1n, or to C4n.2n. For a unique correlation, however, additional palaeomagnetic data is required from the upper and lower parts of the section.

Pumice beds of the Maragheh Formation, which is distributed on the plains at the foot of the late Cenozoic Sahand volcano, NW Iran, consist of the Mordaq tuff bed, lower pumice beds (A and B), middle pumice bed and upper pumice bed, in ascending order. New hornblende and plagioclase K–Ar ages of the pumices from these are: Mordaq tuff bed: 8.14 ± 0.27 Ma, lower pumice beds (A): 7.54 ± 0.22 Ma, lower pumice beds (B): 6.95 ± 0.28 Ma, middle pumice bed: 7.87 ± 0.29 Ma, upper pumice bed: 6.96 ± 0.31 Ma. The middle pumice bed is a flood deposit, and the chemical compositions of glass, hornblende and biotite in pumices overlap those from the lower pumice beds (A). These features indicate that the pumices of the middle pumice bed were derived from a similar source to the lower pumice beds (A). Chemical compositions of pumices from the Maragheh Formation fall in the dacite field of the total alkali-silica (TAS) classification diagram and slightly differ from those of the Plio–Pleistocene rocks from the Sahand volcano. Chemical compositions of late Miocene Maragheh Formation pumices show adakitic features with high Sr contents (698–545 ppm), and low Y (12–8 ppm). It is inferred that the source materials of the adakitic dacite magma were amphibole eclogite or garnet amphibolite originating from the Neo-Thetys plate subducted beneath the Eurasia plate.

Miocene hominoid fossils are known from Africa and Eurasia, in the latter ranging widely from western Europe to Anatolia and from South Asia to Southeast/East Asia. Iran is located between the known western and eastern Eurasian hominoid distributions and is potentially important in understanding Miocene hominoid dispersal patterns. Maragheh is a late Miocene fossil locality in northwestern Iran, well known since the nineteenth century for its abundant mammalian fossils. However, until now, the only primate fossils reported from Maragheh or Iran were the Old World monkey Mesopithecus pentelicus. Recent field research at Maragheh has changed this situation by the discovery of the first hominoid fossil from Iran, a maxillary fragment with well-preserved second and third molars. Here, we provide a detailed description of this new specimen, comparing it with other similarly large-sized Eurasian late Miocene hominoids, Ouranopithecus, Ankarapithecus, Sivapithecus, and Indopithecus. Molar morphology of the Maragheh hominoid is similar to that of these Eurasian Miocene genera, with only minor differences in morphology and wear pattern. Based on the presently available materials, we tentatively prefer the interpretation that the Maragheh hominoid may be related more closely to either Ankarapithecus or Sivapithecus rather than to Ouranopithecus, but the fragmentary nature of the fossil makes evaluations difficult. Future discoveries of this Iranian hominoid are needed to determine its phylogenetic position with more certainty.

Most suids (Mammalia: Suidae, pigs) worldwide are omnivores living in closed environments, but the African warthog (Phacochoerus) has special adaptations for grazing in open environments. Similar specializations have been recorded from Plio-Pleistocene African suids. Four genera, Nyanzachoerus, Notochoerus, Kolpochoerus, and Metridiochoerus, have been discovered in late Miocene to middle Pleistocene locations around the Turkana Basin. We analyse the relative abundances of these four suid genera compared to other mammals, from approximately 8-0.7 Ma. The dataset includes most of the mammal specimens collected from locations around the Kenyan side of the Turkana Basin. Species of genus Nyanzachoerus were dominant before 4 Ma, but their relative abundance decreases through time thereafter. At the same time, Notochoerus increases in relative abundance, followed by Kolpochoerus, and finally Metridiochoerus. Their peak relative abundances do not overlap: Notochoerus peaks at 3.44-2.53 Ma, Kolpochoerus at 2.53-1.87 Ma, and Metridiochoerus at 1.38-0.7 Ma. We interpret the palaeoecology of these suids based on their relative abundances over time and on published isotope and pollen data. We find that Nyanzachoerus was replaced by its abrasive-diet-specialized successor Notochoerus, possibly in response to a rapid decrease in forest cover. Notochoerus adapted at first to the expanding wood- and grasslands, and then to more arid shrublands. After a period of severe aridity around 2.7-2.5 Ma, more variable environments allowed Kolpochoerus and Metridiochoerus to disperse, while Notochoerus disappeared, perhaps having lost its competitive edge. Further changes in the environment encouraged the expansion of grasslands over shrublands, favouring Metridiochoerus. Kolpochoerus persisted in the more closed environments near water sources.

Damiao, Inner Mongolia, has three main fossil horizons representing the early, middle, and late Miocene. The middle Miocene locality DM01 is the only primate locality from the region and also represents the latest occurrence of pliopithecoids in northern China. The presence of pliopithecoid primates in central Asia after the middle Miocene climatic optimum seems to contradict the general trend of strengthening climatic zonality and increasing aridity. To investigate this enigma, we employ faunal similarity, ecometrics, and stable isotope analysis. Our results support previous inferences concerning the presence of locally humid environments within the increasingly arid surroundings that characterized central Asia. Hypsodonty, estimated mean annual precipitation (MAP), local sedimentology, and large mammal fossils suggest more humid and possibly more forested and wooded environments for the DM01 locality. We compared our results with the adjacent fossil-rich middle Miocene Tunggur localities. However, the small mammal fauna and isotope data are consistent with a mosaic of forest and grassland environment for all Damiao localities. Based on our results, Tunggur may have been too seasonal or not sufficiently humid for pliopithecids. This is supported by the higher mean hypsodonty and lower estimated MAP estimates, as well as slightly higher d13C values. We suggest that DM01, the driest known Asian pliopithecid locality, may have been a more humid refugium within a generally drier regional context.

Although patterns of tooth wear are crucial in palaeo-reconstructions, and dental wear abnormalities are important in veterinary medicine, experimental investigations on the relationship between diet abrasiveness and tooth wear are rare. Here, we investigated the effect of four different pelleted diets of increasing abrasiveness (due to both internal [phytoliths] and external abrasives [sand]) or whole grass hay fed for two weeks each in random order to 16 rabbits (Oryctolagus cuniculus) on incisor and premolar growth and wear, and incisor and cheek tooth length. Wear and tooth length differed between diets, with significant effects of both internal and external abrasives. While diet abrasiveness was linked to tooth length for all tooth positions, whole forage had an additional effect on upper incisor length only. Tooth growth was strongly related to tooth wear and differed correspondingly between diets and tooth positions. At 1.4-3.2 mm per week, the growth of cheek teeth measured in this study was higher than previously reported for rabbits. Dental abnormalities were most distinct on the diet with sand. This study demonstrates that concepts of constant tooth growth in rabbits requiring consistent wear are inappropriate, and that diet form (whole vs. pelleted) does not necessarily affect cheek teeth. Irrespective of the strong effect of external abrasives, internal abrasives have the potential to induce wear and hence exert selective pressure in evolution. Detailed differences in wear effects between tooth positions allow inferences about the mastication process. Elucidating feedback mechanisms that link growth to tooth-specific wear represents a promising area of future research.

The evolution of a particular sensory organ is often discussed with no consideration of the roles played by other senses. Here, we treat mammalian vision, olfaction and hearing as an interconnected whole, a three-dimensional sensory space, evolving in response to ecological challenges. Until now, there has been no quantitative method for estimating how much a particular animal invests in its different senses. We propose an anatomical measure based on sensory organ sizes. Dimensions of functional importance are defined and measured, and normalized in relation to animal mass. For 119 taxonomically and ecologically diverse species, we can define the position of the species in a three-dimensional sensory space. Thus, we can ask questions related to possible trade-off vs. co-operation among senses. More generally, our method allows morphologists to identify sensory organ combinations that are characteristic of particular ecological niches. After normalization for animal size, we note that arboreal mammals tend to have larger eyes and smaller noses than terrestrial mammals. On the other hand, we observe a strong correlation between eyes and ears, indicating that co-operation between vision and hearing is a general mammalian feature. For some groups of mammals we note a correlation, and possible co-operation between olfaction and whiskers.

Author correction: vol 2, pg, 402, 2018 DOI:10.1038/s41559-018-0468-8 Despite much interest in the ecology and origins of the extensive grassland ecosystems of the modern world, the biogeographic relationships of savannah palaeobiomes of Africa, India and mainland Eurasia have remained unclear. Here we assemble the most recent data from the Neogene mammal fossil record in order to map the biogeographic development of Old World mammalian faunas in relation to palaeoenvironmental conditions. Using genus-level faunal similarity and mean ordinated hypsodonty in combination with palaeoclimate modelling, we show that savannah faunas developed as a spatially and temporally connected entity that we term the Old World savannah palaeobiome. The Old World savannah palaeobiome flourished under the influence of middle and late Miocene global cooling and aridification, which resulted in the spread of open habitats across vast continental areas. This extensive biome fragmented into Eurasian and African branches due to increased aridification in North Africa and Arabia during the late Miocene. Its Eurasian branches had mostly disappeared by the end of the Miocene, but the African branch survived and eventually contributed to the development of Plio-Pleistocene African savannah faunas, including their early hominins. The modern African savannah fauna is thus a continuation of the extensive Old World savannah palaeobiome.

We discuss a proboscidean bone fragment discovered in southern Finland, including the morphological analysis of the bone, as well as pollen and diatom analyses from sediment contained in the marrow cavity. Preliminary analysis of the bone suggested petrification and thus an apparently old age, while the microfossil assemblages include numerous unequivocally pre-Quaternary pollen, spore, and diatom types. A Miocene age for the bone is determined based on the presence of the diatom genus Alveolophora , indicating a minimum age of 5 Ma, and based on the earliest appearance of proboscideans outside Africa, setting a maximum age of 19 Ma. Based on morphology, the bone is determined as a partial humerus of the left foreleg of a large proboscidean. The bone is tentatively assigned to cf. Deinotherium sp., which is consistent with the diatom-based minimum age. The pollen assemblage is rich in spores of shoreline pteridophytes, while the diatom assemblage is also consistent with a shoreline freshwater environment, suggesting that the bone was deposited post-mortem near the shore of a lake or a stream. Miocene sediments do not currently exist in southern Finland or in the near vicinity. This implies that the bone has been transported over a considerable distance. Due to the discovery of the bone in early-Holocene Baltic Sea clay, the final transport phase and deposition must have taken place via iceberg rafting. This was likely preceded by one or more phases of glacial and/or glacio-fluvial transport. While we are unable to conclusive ascertain the region of origin, the alkaline composition of the contained sediment and diatoms point towards the Russian Plain region in the east. This specimen represents the oldest mammalian bone discovered in Finland and the northernmost discovery of a Miocene proboscidean bone in Europe.

Aim Our aims were to test: (1) the extent to which vascular plant associations are related in space to mammalian associations, and (2) whether the plant associations are more closely related than the mammalian associations to climate and to a published environmental stratification of Europe. Location Europe, as defined by the following boundaries: 11� W, 32� E, 71� N and 35� N. Methods The analysis is based on presence/absence records of mammal species and plant species with a resolution of 50 km · 50 km. The similarity of the overall spatial structure was tested using a partial Mantel test while controlling for the effect of geographical proximity. To further identify the main spatial components in the datasets, we used k-means clustering and principal components analysis. The resulting geographical patterns were compared with one another, with climate variables and with the environmental stratification of Europe. Results The clustering of the plant data forms coherent areas that can be interpreted as reflections of floristic regions that are controlled to a large extent by climate and topography. In terms of the correlation between distance matrices, the relationship between plants and mammals is relatively strong. The relationships between mammals and climate, and between plants and climate, are more complex but always statistically significant. There is no evidence that the plant clusters are more closely related than the mammalian clusters to climate, although plant clusters are closer to environmental data than to climate. Main conclusions The clustering patterns of mammals and plants form groups that agree with one another in their spatial extent. The forcing of floristic patterns into coherent entities appears mainly to be caused by climatic variables (temperature, temperature range and rainfall), mediated by elevation differences. The formation of individual plant clusters is also related to species numbers and to local and regional floristic differences. The close correlation between the floristic and faunal patterns suggests that the mammal and plant distributions are controlled by the same environmental variables, although the extent to which the mammals are controlled directly by climate or through the influence of vegetation requires more detailed study.

1. The evolution of high-crowned teeth or hypsodonty in herbivorous mammals is widely interpreted as a species-specific adaptation to increasingly wear-inducing diets and environments at evolutionary time scales, with internal abrasives (such as phytoliths in grasses) and/or external abrasives (such as dust or grit) as putative causative factors. The mesowear score (MS) instead describes tooth wear experienced by individual animals during their lifetime. 2. Under the assumption that the abrasiveness that causes the MS in individuals is the same abrasiveness to which species adapted by evolving hypsodonty, one would expect a close correlation between the MS and the hypsodonty index (HI). Alternatively, if these two measures reflect different aspects of wear, one would expect differences in the way that proxies of diet or environment/climate correlate with each parameter. 3. In order to test these hypotheses, we collated a dataset on the HI, MS, percentage of grass in the natural diet (%grass), habitat (open, intermediate, closed) and annual precipitation (PREC) in extant mammalian herbivores. The availability of a quantitative MS constrained the dataset to 75 species. Data were analysed with and without phylogenetic generalized least squares (PGLS). 4. Correlations with PREC were stronger for HI than for MS, whereas correlations with %grass were similar for HI and MS. Habitat had a significant influence on the relationship with %grass for HI but not for MS. Habitat also had a significant influence on the relationship between HI and MS. MS improved the predictive power of HI for %grass, but not for PREC. 5. These results suggest that while the MS indicates predominantly the wear effect of the diet (internal abrasives), HI represents an adaptation to a wear effect that comprises both diet and environment (external abrasives). The additional environmental wear effect must reduce tooth height without causing macroscopic changes in tooth facet development as described by the MS. 6. The most parsimonious explanation for the apparent discrepancy between HI and MS is that external abrasives of very fine particle size play a major role in naturally occurring tooth wear. The experimental testing of this hypothesis will enhance our understanding of the processes involved in tooth wear.

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.

One of the classic examples of faunal turnover in the fossil record is the Miocene transition from faunas dominated by anchitheriine horses with low-crowned molar teeth to faunas with hipparionine horses characterized by high-crowned teeth. The spread of hipparionine horses is associated with increased seasonality and the expansion of open habitats. It is generally accepted that anchitheriine horses did not display an evolutionary increase in tooth crown height prior to their extinction. Nevertheless, to test whether anchitheriines showed any changes interpretable as adaptation to local conditions, we analyzed molar teeth from multiple populations of Anchitherium in three dimensions. Our results show differences in tooth morphology that suggest incipient hypsodonty in Spain, the first region experiencing increasingly arid conditions in the early Miocene of Europe. Furthermore, analyses of tooth wear show that Spanish specimens cluster with present ungulates that eat foliage together with grasses and shrubs, whereas German specimens cluster with present-day ungulates that eat mostly foliage. Taken together, even a taxon such as Anchitherium, with a long and successful history of forest adaptation, did respond to regional environmental changes in an adaptive manner.

In the version of this Article originally published, each of the five panels in Fig. 5 incorrectly contained a black diagonal line across the plot. This has now been corrected.

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.

An ever larger proportion of Earth's biota is affected by the current accelerating environmental change. The mismatches be- tween organisms and their environments are now increasing in both magnitude and frequency, resulting in lowered fitness and hence the decline of populations. Under this scenario, species with behavioral and/or physiological traits that provide them shelter from the en- vironment are predicted to be less vulnerable to population declines than species that are always exposed to the elements. Here, we coded 4,536 living mammal species for sleep-or-hide (SLOH) behavior, including hibernation, torpor, and the use of burrows, among other related traits. We demonstrate that species that exhibit SLOH be- havior are underrepresented in high-risk International Union for Conservation of Nature Red List categories. We found that SLOH behavior contributes to lowering extinction risk even after we ac- counted for other factors that directly or indirectly buffer species against extinction, such as larger geographic ranges and smaller body sizes. This result is robust to analyses using phylogenetically inde- pendent contrasts. Sleep-or-hide behavior, made possible by a related suite of physiological adaptations, allows mammals to function at lower metabolic rates and/or buffer them from changing physical elements. Mammals with SLOH behavior have a greater propensity to survive in the current extinction crisis and probably also in past crises because of reduced exposure to environmental stress.

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.

Aim To produce a spatial clustering of Europe on the basis of species occurrence data for the land mammal fauna.

The path of species diversification is commonly observed by inspecting the fossil record. Yet, how species diversity changes at geological timescales relate to lower-level processes remains poorly understood. Here we use mathematical models of spatially structured populations to show that natural selection and gradual environmental change give rise to discontinuous phenotype changes that can be connected to speciation and extinction at the macroevolutionary level. In our model, new phenotypes arise in the middle of the environmental gradient, while newly appearing environments are filled by existing phenotypes shifting their adaptive optima. Slow environmental change leads to loss of phenotypes in the middle of the extant environmental range, whereas fast change causes extinction at one extreme of the environmental range. We compared our model predictions against a well-known yet partially unexplained pattern of intense hoofed mammal diversification associated with grassland expansion during the Late Miocene. We additionally used the model outcomes to cast new insight into Cope’s law of the unspecialized. Our general finding is that the rate of environmental change determines where generation and loss of diversity occur in the phenotypic and physical spaces. © 2015 by The University of Chicago.

Fil: Raia, Pasquale. Università degli Studi di Napoli Federico II; Italia Fil: Passaro, Federico. Università degli Studi di Napoli Federico II; Italia Fil: Carotenuto, Francesco. Università degli Studi di Napoli Federico II; Italia Fil: Maiorino, Leonardo. Università degli Studi Roma Tre; Italia Fil: Piras, Paolo. Università degli Studi Roma Tre; Italia Fil: Teresi, Luciano. Università degli Studi Roma Tre; Italia Fil: Meiri, Shai. Tel Aviv University; Israel Fil: Itescu, Yuval. Tel Aviv University; Israel Fil: Novosolov, Maria. Tel Aviv University; Israel Fil: Baiano, Mattia A. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fil: Baiano, Mattia A. Instituto Catalán de Paleontología Miquel Crusafont; España Fil: Baiano, Mattia A. Universidad Nacional de Río Negro; Argentina Fil: Martínez, Ricard. Universitat Autònoma de Barcelona; España Fil: Fortelius, Mikael. University Of Helsinski; Finlandia Luxuriant, bushy antlers, bizarre crests, and huge, twisting horns and tusks are conventionally understood as products of sexual selection. This view stems from both direct observation and from the empirical finding that the size of these structures grows faster than body size (i.e., ornament size shows positive allometry).We contend that the familiar evolutionary increase in the complexity of ornaments over time in many animal clades is decoupled from ornament size evolution. Increased body size comes with extended growth. Since growth scales to the quarter power of body size, we predicted that ornament complexity should scale according to the quarter power law as well, irrespective of the role of sexual selection in the evolution and function of the ornament. To test this hypothesis, we selected three clades (ammonites, deer, and ceratopsian dinosaurs) whose species bore ornaments that differ in terms of the importance of sexual selection to their evolution.We found that the exponent of the regression of ornament complexity to body size is the same for the three groups and is statistically indistinguishable from0.25.We suggest that the evolution of ornament complexity is a by-product of Cope’s rule. We argue that although sexual selection may control size in most ornaments, it does not influence their shape.

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.

In their technical comment Salesa et al. (2011) raise several issues, including an important topic affecting most, or perhaps all, paleoecological studies—the difficulty of determining a reasonable way to deal with taxonomy. Specifically, Salesa et al. draw our attention to a taxonomic revision of Iberian Anchitherium (Sanchez et al. 1998), that we failed to follow in our study (Eronen et al. 2010), and express concerns that a different handling of Anchitherium taxonomy would have affected our results and conclusions.

Both pliopithecoid and hominoid primates were widely distributed throughout Eurasia during the Miocene but are known to have coexisted at only a few localities. It has been speculated that their different habitat preferences permitted only minimal overlap under special environmental conditions. Here we study the context for pliopithecoid and hominoid co-occurrence by assessing taxonomically-based palaeoecological diversity of associated fossil mammals and by direct ecometric analysis based on hypsodonty of mammalian herbivores. Our results show that pliopithecoids persistently inhabited more humid environments compared to the other primate groups studied, suggesting an inability to adapt to changing environmental conditions. The opportunity for hominoids and pliopithecoids to co-occur appears to have been restricted by niche conservatism in the latter group. Our study also indicates that direct ecometric analysis gives a better separation of the ecological preferences of these primate clades than do analyses of taxonomically-based community structure.

cited By 22; International audience; Aim: To propose a unified framework for quantifying taxon (Tβ), phylogenetic (Pβ) and functional (Fβ) beta diversity via pairwise comparisons of communities, which allows these types of beta diversity to be partitioned into ecologically meaningful additive components. Location: Global, with case studies in Europe and the Azores archipelago. Methods: Using trees as a common representation for taxon, phylogenetic and functional diversity, we partition total beta diversity (βtotal) into its replacement (turnover, βrepl) and richness difference (βrich) components according to which part of a global tree was shared by or unique to communities that were being compared. We demonstrate the application of this framework using artificial and empirical examples (mammals in Europe and epigean arthropods in the Azores). Results: Our empirical examples show that comparing Pβ and Fβ with the most commonly used Tβ revealed previously hidden patterns of beta diversity. More importantly, we demonstrate that partitioning Pβtotal and Fβtotal into their respective βrepl and βrich components facilitates the detection of more complex patterns than using the overall coefficients alone, further elucidating the different forces operating in community assembly. Main conclusions: The methods presented here allow the integration and full comparison of Tβ, Pβ and Fβ. They provide a tool for effectively disentangling the replacement (turnover) and richness difference components of the different biodiversity facets within the same methodological framework. © 2013 John Wiley & Sons Ltd.

In Heikinheimo et al. (Journal of Biogeography, 2007, 34, 1053–1064) we used clustering to analyse European land mammal fauna. Gagne & Proulx criticized our choice of the Euclidean distance measure in the analysis, and advocated the use of the Hellinger distance measure, claiming that this leads to very different clustering results. The criticism fails to take into account the probabilistic nature of the methods used and the fact that in this case the similarity measures correlate strongly. Gagne & Proulx used subjective inspection as the criterion of similarity between clusterings. We show that this is insufficient and misleading. Namely, owing to the local minimum problem, two clustering runs rarely give identical results. In the case of our study, the measured similarity (using the kappa statistic) between the Euclidean- and Hellinger-based clusterings is roughly equal to the similarity between two clusterings that both use the Hellinger distance but different random initialization points.

The Oligocene giant rhinocerotoid Indricotherium transouralicum (= Baluchitherium grangeri ), 'the largest mammal that ever lived,' was smaller than is generally believed. Over 90 estimates based on head-and-body length, skull size, molar length and proximal limb bone diameters agree well on a mean mass estimate of about 11 tonnes (t) rather than the 20-30 t given by most texts. A maximum mass estimate between 15 and 20 t seems probable. Marked sexual dimorphism is possible but the material is insufficient to assess the problem property. The single source of the inflated, widely cited mass estimates seems to be the famous Granger-Gregory-Ziska reconstruction from 1935-36, which was itself inflated by arbitrary, isometric scaling up of individual elements to a hypothetical maximum size. Paraceratherium bugtiense and P. prohorovi seem to have been somewhat smaller than I. transouralicum . The largest indricotheres were similar in size to the largest fossil proboscideans, and extend the known size range of terrestrial mammals marginally if at all.

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.

Commonness of organisms typically fluctuates through time, and understanding such fluctuations has long been an important part of ecological research. Studies at paleontological timescales provide a perspective on how changes in population size might affect community structure over millions of years. To overcome the obstacle that population size parameters such as abundance are difficult to detect in the fossil record, we here used fossil locality coverage to approximate changes in site occupancy in the Neogene of Europe over the course of 20 million years. Our aim was to examine whether the trophic structure of mammalian communities is maintained through time despite continuing environmental change. Ecomorphological grouping of fossils indicates that herbivore genera have low taxon resilience in that each genus has predominantly only one locality coverage peak before disappearance. Despite this continuous replacement of the most prevalent herbivore genera, the herbivore trophic group as a whole remains the largest and maintains a roughly constant share of locality coverage throughout the Neogene. The successive herbivore genera, however, show increasing adaptations to harshening environments, indicating shifting properties of niches while the overall trophic structure is conserved. Carnivores, dependent on primary productivity for food indirectly through their prey, show moderate lack of resilience. In contrast, in omnivores changes in locality coverage are close to random fluctuations.

Book reviewed in this article: Bryan, A. L. (ed.) 1986: New Evidence for the Pleistocene Peopling of the Americas

Kahasa. J. (ed) IY84: Quorrrriury of South Afrierrco and Antarctic Penusula A. A. Balksma. Rotterdam.

Book reviewed in this article: Bjorn Kurttn & Elaine Anderson: Pleistocene Mammals of North America

Vertical enamel prism decussation in the inner-layer enamel of rhinoceroses occurs as the result of vertical translation, in opposite senses, of zones of ameloblasts, which begins very shortly after amelogenesis commences at the enamel-dentine junction. Prisms in the centre of the decussating zones are stacked in the Pattern 3 arrangement. Zone boundary prisms adopt intermediate orientations, are locally nearly perpendicular to the enamel surface, and have a cylindrical, Pattern 1 cross-section. Decussation also continues in the outer-layer enamel, but the prisms all have occlusal-going courses: the occlusal-going zones of the inner enamel continue as the more occlusally oriented zones of the outer layer. Abrasion resistance to diamond polishing and soft abrasive projectile erosion (air-polishing with NaHCOs) and resistance to ion beam erosion is greater with distance from the nearest prism boundary discontinuity. Polished surface areas containing longitudinally sectioned prisms are more prone to ‘air-polishing’ and ‘airbrading’ erosion than areas with transversely sectioned prisms. These observed relationships fully explain the relief developed at natural wear surfaces.

By digitizing the enamel configuration and calculating the overall directional tendencies of the enamel edges in complex equid dental patterns, quantitative changes in functional attributes were traced through a phylogenetic series. Pronounced changes both in the directional emphasis of the enamel edges and in the chewing motion occurred and were interrelated. Two distinct trends were found. From early Eocene to Oligocene, edge alignment became increasingly confined to a single direction, but the teeth retained the phase I and phase II chewing angles characteristic of many primitive herbivorous and omnivorous mammals. The chewing direction in the horizontal plane also remained essentially unchanged. During the Oligocene and the early Miocene, both edge direction and chewing direction remained stable. However, the middle Miocene genus Merychippus represents a stage in which the enamel directional emphasis was lost in transition to a new anteroposterior emphasis, a trend that continued into the late Tertiary equine taxa. Concurrent with this transformation was a loss of all but vestiges of the phase I and II chewing angles in the vertical plane and a shift of the chewing direction in the horizontal plane to an almost transverse movement of the jaw.In the Oligocene equids, the edges of the labial cusps did attain perpendicularity to the phase I chewing direction, which was oblique to the horizontal plane, but the chewing direction in the horizontal plane was far from perpendicular to the lingual enamel edge direction because the lingual cusps were configured for efficiency in compressive, not shearing, motion that dominated the phase II surfaces. In the later Tertiary the chewing direction and edges attained essentially a perpendicular relationship, which represents the theoretical optimum for a shearing system. The radical change in edge direction in the Miocene probably occurred as a result of an increase in translative movement (longer glide) between the surfaces, making the lingual edges subject to selection for perpendicularity and flattening of the occlusal surface, resulting in a condition where a single edge direction became optimal for all cusps. The extended chewing stroke translation was perhaps the key event initiating the other changes and would have resulted from increased chewing effort accompanying a shift to a diet of mainly grass. The loss of the dual (shearing and compressive) function of the occlusal surface suggests that the earlier diet may have contained significant proportions of other plant parts, such as fruits, seeds, or tender leaves that might be optimally chewed by compressive movements.