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A new species of bothriodontine anthracothere, Arretotherium meridionale, is described from the early Miocene (Arikareean North America Land Mammal Age) Las Cascadas fossil assemblage in Panama, Central America. Fossils of A. meridionale are the first record of an anthracothere from the New World Tropics. Among anthracotheres, A. meridionale is most similar to A. acridens from the middle Arikareean from Texas in having a relatively deep and robust jaw, high and sharp cusps on the lower molars, short c-p1 diastema, and absence of a mesiolingual metacristid. A. meridionale differs from other species in being generally larger, two lower incisors (rather than three), prehypocristid never reaching the postprotocristid, more apical junction between postprotocristid and postmetacristid, mesiolingual entocristid transversely notching preentocrisitid, and transverse valley tapered lingually by prehypocristid. Although cladistic analysis of 28 anthracotheriids coded for 51 characters supports a relationship between A. meridionale and A. acridens, some presumably convergent dental characteristics are also similar to certain Oligocene-Miocene Eurasian bothriodontines. The presence of Arretotherium in the Las Cascadas Formation in Panama, and absence in the later Centenario Fauna, shows that primitive bothriodontines entered into Central America by the early Miocene before disappearing from the New World during the late early-middle Miocene.

Tooth enamel microstructure is a reliable and widely used indicator of dietary interpretations and data for phylogenetic reconstruction, if all levels of variability are investigated. It is usually difficult to have a thorough examination at all levels of enamel structures for any mammals, especially for the early mammals, which are commonly represented by sparse specimens. Because of the random preservation of specimens, enamel microstructures from different teeth in various species are often compared. There are few examples that convincingly show intraspecific variation of tooth enamel microstructure in full dentition of a species, including multituberculates. Here we present a systematic survey of tooth enamel microstructures of Lambdopsalis bulla, a taeniolabidoid multituberculate from the Late Paleocene Nomogen Formation, Inner Mongolia. We examined enamel structures at all hierarchical levels. The samples are treated differently in section orientations and acid preparation and examined using different imaging methods. The results show that, except for preparation artifacts, the crystallites, enamel types, Schmelzmuster and dentition types of Lambdopsalis are relatively consistent in all permanent teeth, but the prism type, including the prism shape, size and density, may vary in different portions of a single tooth or among different teeth of an individual animal. The most common Schmelzmuster of the permanent teeth in Lambdopsalis is a combination of radial enamel in the inner and middle layers, aprismatic enamel in the outer layer, and irregular decussations in tooth crown area with great curvature. The prism seam is another comparably stable characteristic that may be a useful feature for multituberculate taxonomy. The systematic documentation of enamel structures in Lambdopsalis may be generalized for the enamel microstructure study, and thus for taxonomy and phylogenetic reconstruction, of multituberculates and even informative for the enamel study of other early mammals.

The super(15)N/ super(14)N signature of animal proteins is now commonly used to understand their physiology and quantify the flows of nutrient in trophic webs. These studies assume that animals are predictably super(15)N-enriched relative to their food, but the isotopic mechanism which accounts for this enrichment remains unknown. We developed a box model of the nitrogen isotope cycle in mammals in order to predict the super(15)N/ super(14)N ratios of body reservoirs as a function of time, N intake and body mass. Results of modeling show that a combination of kinetic isotope fractionation during the N transfer between amines and equilibrium fractionation related to the reversible conversion of N-amine into ammonia is required to account for the well-established approximately 4ppt super(15)N-enrichment of body proteins relative to the diet. This isotopic enrichment observed in proteins is due to the partial recycling of super(15)N-enriched urea and the urinary excretion of a fraction of the strongly super(15)N-depleted ammonia reservoir. For a given body mass and diet delta super(15)N, the isotopic compositions are mainly controlled by the N intake. Increase of the urea turnover combined with a decrease of the N intake lead to calculate a delta super(15)N increase of the proteins, in agreement with the observed increase of collagen delta super(15)N of herbivorous animals with aridity. We further show that the low delta super(15)N collagen values of cave bears cannot be attributed to the dormancy periods as it is commonly thought, but inversely to the hyperphagia behavior. This model highlights the need for experimental investigations performed with large mammals in order to improve our understanding of natural variations of delta super(15)N collagen.

Accurate taxonomy is central to the study of biological diversity, as it provides the needed evolutionary framework for taxon sampling and interpreting results. While the number of recognized species in the class Mammalia has increased through time, tabulation of those increases has relied on the sporadic release of revisionary compendia like the Mammal Species of the World (MSW) series. Here, we present the Mammal Diversity Database (MDD), a digital, publically accessible, and updateable list of all mammalian species, now available online: https://mammaldiversity.org. The MDD will continue to be updated as manuscripts describing new species and higher taxonomic changes are released. Starting from the baseline of the 3rd edition of MSW (MSW3), we performed a review of taxonomic changes published since 2004 and digitally linked species names to their original descriptions and subsequent revisionary articles in an interactive, hierarchical database. We found 6,495 species of currently recognized mammals (96 recently extinct, 6,399 extant), compared to 5,416 in MSW3 (75 extinct, 5,341 extant)—an increase of 1,079 species in about 13 years, including 11 species newly described as having gone extinct in the last 500 years. We tabulate 1,251 new species recognitions, at least 172 unions, and multiple major, higher-level changes, including an additional 88 genera (1,314 now, compared to 1,226 in MSW3) and 14 newly recognized families (167 compared to 153). Analyses of the description of new species through time and across biogeographic regions show a long-term global rate of ~25 species recognized per year, with the Neotropics as the overall most species-dense biogeographic region for mammals, followed closely by the Afrotropics. The MDD provides the mammalogical community with an updateable online database of taxonomic changes, joining digital efforts already established for amphibians (AmphibiaWeb, AMNH's Amphibian Species of the World), birds (e.g., Avibase, IOC World Bird List, HBW Alive), non-avian reptiles (The Reptile Database), and fish (e.g., FishBase, Catalog of Fishes). Una taxonomía que precisamente refleje la realidad biológica es fundamental para el estudio de la diversidad de la vida, ya que proporciona el armazón evolutivo necesario para el muestreo de taxones e interpretación de resultados del mismo. Si bien el número de especies reconocidas en la clase Mammalia ha aumentado con el tiempo, la tabulación de esos aumentos se ha basado en las esporádicas publicaciones de compendios de revisiones taxonómicas, tales como la serie Especies de mamíferos del mundo (MSW por sus siglas en inglés). En este trabajo presentamos la Base de Datos de Diversidad de Mamíferos (MDD por sus siglas en inglés): una lista digital de todas las especies de mamíferos, actualizable y accesible públicamente, disponible en la dirección URL https://mammaldiversity.org/. El MDD se actualizará con regularidad a medida que se publiquen artículos que describan nuevas especies o que introduzcan cambios de diferentes categorías taxonómicas. Con la tercera edición de MSW (MSW3) como punto de partida, realizamos una revisión en profundidad de los cambios taxonómicos publicados a partir del 2004. Los nombres de las especies nuevamente descriptas (o ascendidas a partir de subespecies) fueron conectadas digitalmente en una base de datos interactiva y jerárquica con sus descripciones originales y con artículos de revisión posteriores. Los datos indican que existen actualmente 6,495 especies de mamíferos (96 extintas, 6,399 vivientes), en comparación con las 5,416 reconocidas en MSW3 (75 extintas, 5,341 vivientes): un aumento de 1,079 especies en aproximadamente 13 años, incluyendo 11 nuevas especies consideradas extintas en los últimos 500 años. Señalamos 1,251 nuevos reconocimientos de especies, al menos 172 uniones y varios cambios a mayor nivel taxonómico, incluyendo 88 géneros adicionales (1,314 reconocidos, comparados con 1,226 en MSW3) y 14 familias recién reconocidas (167 en comparación con 153 en MSW3). Los análisis témporo-geográficos de descripciones de nuevas especies (en las principales regiones del mundo) sugieren un promedio mundial de descripciones a largo plazo de aproximadamente 25 especies reconocidas por año, siendo el Neotrópico la región con mayor densidad de especies de mamíferos en el mundo, seguida de cerca por la region Afrotrópical. El MDD proporciona a la comunidad de mastozoólogos una base de datos de cambios taxonómicos conectada y actualizable, que se suma a los esfuerzos digitales ya establecidos para anfibios (AmphibiaWeb, Amphibian Species of the World), aves (p. ej., Avibase, IOC World Bird List, HBW Alive), reptiles “no voladores” (The Reptile Database), y peces (p. ej., FishBase, Catalog of Fishes).

Aim: To investigate the validity of Simpson's model of sweepstakes dispersal, particularly as it applies to the colonization of Madagascar by African mammals. We chose lemurs as a classic case. Location: The East African coast, the Mozambique Channel and Madagascar. Methods: First, we investigated the assumptions underlying Simpson's statistical model as it relates to dispersal events. Second, we modelled the fate of a natural raft carrying one or several migrating mammals under a range of environmental conditions: in the absence of winds or currents, in the presence of winds and currents, and with and without a sail. Finally, we investigated the possibility of an animal being transported across the Mozambique Channel by an extreme climatic event like a tornado or a cyclone. Results: Our investigations show that Simpson's assumptions are consistently violated when applied to scenarios of over-water dispersal by mammals. We suggest that a simple binomial probability model is an inappropriate basis for extrapolating the likelihood of dispersal events. One possible alternative is to use a geometric probability model. Our estimates of current and wind trajectories show that the most likely fate for a raft emerging from an estuary on the east coast of Africa is to follow the Mozambique current and become beached back on the African coast. Given prevailing winds and currents, transport from Madagascar to Africa is very much more likely than the reverse process. Freak transport by means of a hurricane or tornado is even less likely than rafting for mammals. Main conclusions: Our models suggest that the scenario of sweepstakes dispersal that currently enjoys wide support is not valid at either the theoretical or the applied level when applied to the hypothetical invasion of Madagascar by African mammals. Alternative explanations should be sought.

Aims: To describe the pattern of mean body size of native mammals in Europe, and to investigate its relationships with environmental predictors related to four hypotheses: (1) dispersal; (2) heat conservation; (3) heat dissipation; and (4) resource availability. Location: Continental western Europe and Great Britain. Methods: We used range maps to estimate the mean body size (average log mass) of mammals in 386 cells of 12,100 km super(2) each. Environmental conditions in each cell were quantified using nine historical, climatic and primary production variables. We attempted to tease apart the effects of these variables using correlation, multiple regression and spatial autocorrelation analyses. Results: In the part of the continent covered by ice during the Pleistocene, body mass decreases southwards, and annual average temperature explains 73% of the variance in body size, consistent with the heat-conservation hypothesis. However, in warmer, non-glaciated areas the best predictor is an estimate of seasonality in plant production, but it explains only 18% of the variance. Carnivores, omnivores and herbivores show similar relationships, but the pattern for herbivores is substantially weaker than for the other groups. Main conclusions: Overall, the relationship between mean body size and temperature is non-linear, being strong in cold environments but virtually disappearing above a temperature threshold.

Bats are highly charismatic and popular animals that are not only fascinating in their own right, but illustrate most of the topical and important concepts and issues in mammalian biology. This book covers the key aspects of bat biology, including evolution, flight, echolocation, hibernation, reproduction, feeding and roosting ecology, social behaviour, migration, population and community ecology, biogeography, and conservation. This new edition is fully updated and greatly expanded throughout, maintaining the depth and scientific rigour of the first edition. It is beautifully illustrated with drawings and colour photographs.

Well-known examples of high-amplitude, large-scale fluctuations of small-mammal populations include vole cycles in the boreal zone of Eurasia, lemming cycles in the high-arctic tundra of Eurasia and North America, snowshoe hare cycles in the boreal zone of North America, and outbreaks of house mice in southeastern Australia. We synthesize the recent knowledge of three key aspects of these animals' population cyles: (1) periodicity, amplitude, and spatiotemporal synchrony; (2) reproduction and survival; and (3) underlying mechanisms. Survival rather than reproductive rate appears to drive rates of population increase during these fluctuations. Food limitation may stop increases of cyclic vole, lemming, and hare populations, whereas the decline from peak numbers is caused by predation mortality. In house mice, without coevolved predators, outbreaks may be driven by rainfall, food supply, and disease.

In polygynous mammals, it is commonly observed that both sex ratios at birth and dispersal are male biased. This has been interpreted as resulting from low female dispersal causing high female local resource competition, which would select for male-biased sex ratios. However, a female-biased sex ratio can be selected despite lower female than male-biased dispersal. This will occur if the low female dispersal is close to the optimal dispersal rate, while the male dispersal is not close to the optimal dispersal rate. The actual outcome depends on the joint evolution of sex-biased dispersal and sex ratio. Earlier analyses of joint evolution imply that there will be no sex-ratio nor dispersal biases at the joint evolutionarily stable strategy, thus they do not explain the data. However, these earlier analyses assume no intersexual competition for resources. Here, we show that when males and females compete with each other for access to resources, male-biased dispersal will be associated with male-biased birth sex ratio, as is commonly observed. A trend toward male-biased birth sex ratios is also expected if there is intersexual local resource competition and if birth sex ratio is constrained so that it cannot depart from balanced sex ratio.

Baguatherium jaureguii gen. et sp. nov. from the early Oligocene of northern Peru is the best known pre-Deseadan pyrothere. It has a relatively wider palate and less oblique lophs on the molariform teeth than Pyrotherium macfaddeni and Pyrotherium romeroi. A conspicuous lingual crest connects the anterior and posterior lophs of molariform teeth. Nares are retracted. Phylogenetic analysis places Baguatherium with Gryphodon and Pyrotherium in an unresolved polytomy. In Proticia and Colombitherium the wear facets of the molariform teeth indicate a mainly grinding masticatory apparatus. In Pyrotherium, Baguatherium, Gryphodon, and to a lesser degree, Propyrotherium, the oblique wear facets generate a cutting surface caused by a greater antero-posterior component to dorsoventral mastication. The cingulae function like stops or buttresses. Considering its brachydont condition, this specialization and the increase in the molariform surface in Baguatherium and Pyrotherium may have improved masticatory efficiency in response to the expansion of open environments during the Oligocene.