Dental functional morphology predicts the scaling of chewing rate in mammals

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.Peer reviewe

On calibrating the completometer for the mammalian fossil record

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.Peer reviewe

Ihmisen lajikehitys – eli kaamean, karvaisen apinateorian paluu

Ihmisen kuva asemastaan maailmankaikkeudessa on hänen maailmankuvansa ydin, ja se kiteytyy hänen kuvaansa omasta alkuperästään. Olemmeko jumalten jälkeläisiä, langenneita omenansyöjiä, apinoita ekologisella karkumatkalla vai Suuren Vihreän Pärskijän nenästä sinkoutunut, piinallinen erehdys

Relative abundances and palaeoecology of four suid genera in the Turkana Basin, Kenya, during the late Miocene to Pleistocene

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.Peer reviewe

The best of all possible coexistence

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.Peer reviewe

Do species factories exist? Detecting exceptional patterns of evolution in the mammalian fossil record

A species factory refers to the source that gives rise to an exceptionally large number of species. However, what is it exactly: a place, a time or a combination of places, times and environmental conditions, remains unclear. Here we search for species factories computationally, for which we develop statistical approaches to detect origination, extinction and sorting hotspots in space and time in the fossil record. Using data on European Late Cenozoic mammals, we analyse where, how and how often species factories occur, and how they potentially relate to the dynamics of environmental conditions. We find that in the Early Miocene origination hotspots tend to be located in areas with relatively low estimated net primary productivity. Our pilot study shows that species first occurring in origination hotspots tend to have a longer average longevity and a larger geographical range than other species, thus emphasizing the evolutionary importance of the species factories.Peer reviewe

Ancestral feeding state of ruminants reconsidered: earliest grazing adaptation claims a mixed condition for Cervidae

<p>Abstract</p> <p>Background</p> <p>Specialised leaf-eating is almost universally regarded as the ancestral state of all ruminants, yet little evidence can be cited in support of this assumption, apart from the fact that all early ruminants had low crowned cheek teeth. Instead, recent years have seen the emergence evidence contradicting the conventional view that low tooth crowns always indicate leaf-eating and high tooth crowns grass-eating.</p> <p>Results</p> <p>Here we report the results of two independent palaeodietary reconstructions for one of the earliest deer, <it>Procervulus ginsburgi </it>from the Early Miocene of Spain, suggesting that despite having lower tooth crowns than any living ruminant, this species included a significant proportion of grass in its diet.</p> <p>Conclusion</p> <p>The phylogenetic distribution of feeding styles strongly supports that leaf-grass mixed feeding was the original feeding style of deer, and that later dietary specialization on leaves or grass occurred independently in several lineages. Evidence for other ruminant clades suggests that facultative mixed feeding may in fact have been the primitive dietary state of the Ruminantia, which would have been morphologically expressed only under specific environmental factors.</p

Ungulate molars

36 p. : ill. ; 26 cm.Includes bibliographical references (p. 33-35).The analysis of fossil ungulate cheek teeth has long been one of the main sources of information about the terrestrial environments of the Cenozoic, but the methods used to extract this information have been either imprecise or prohibitively laborious. Here we present a method based on relative facet development that is quantitative, robust, and rapid. This method, which we term mesowear analysis, is based on the physical properties of ungulate foods as reflected in the relative amounts of attritive and abrasive wear that they cause on the dental enamel of the occlusal surfaces. Mesowear was recorded by examining the buccal apices of molar tooth cusps. Apices were characterized as sharp, rounded, or blunt, and the valleys between them either high or low. The method has been developed only for selenodont and trilophodont molars, but the principle is readily extendable to other crown types. Mesowear analysis is insensitive to wear stage as long as the very early and very late stages are excluded. Cluster analysis of the mesowear variables produces clusters reflecting four main groups from abrasion-dominated to attrition-dominated: grazers, graze-dominated mixed feeders, browse-dominated mixed feeders, and browsers. Most of the relatively few apparent anomalies are explained by more detailed dietary information. Mesowear analysis provides resolution within the main dietary classes and the clustering is virtually identical with and without the index of hypsodonty. Discriminant analysis using all mesowear variables and hypsodonty showed an overall correct classification of 76% of 64 species of living ungulates into the conventional dietary categories of browser, grazer, and mixed feeder, while a smaller set of 27 "typical" species was correctly classified at 96%. Alternative "conservative" and "radical" dietary classifications that were employed to accommodate cases where dietary information was controversial or unclear produced only marginally different results. Mesowear analysis successfully resolved a test case using the Serengeti grazing succession and appears to be superior to microwear analysis in two cases where the diet of fossil ungulates has been previously studied by microwear and other conventional methods

Small mammal tooth enamel carbon isotope record of C4 grasses in late Neogene China

Peer reviewe