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      Morphometry, Bite-Force, and Paleobiology of the Late Miocene Caiman Purussaurus brasiliensis


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          Purussaurus brasiliensis thrived in the northwestern portion of South America during the Late Miocene. Although substantial material has been recovered since its early discovery, this fossil crocodilian can still be considered as very poorly understood. In the present work, we used regression equations based on modern crocodilians to present novel details about the morphometry, bite-force and paleobiology of this species. According to our results, an adult Purussaurus brasiliensis was estimated to reach around 12.5 m in length, weighing around 8.4 metric tons, with a mean daily food intake of 40.6 kg. It was capable of generating sustained bite forces of 69,000 N (around 7 metric tons-force). The extreme size and strength reached by this animal seems to have allowed it to include a wide range of prey in its diet, making it a top predator in its ecosystem. As an adult, it would have preyed upon large to very large vertebrates, and, being unmatched by any other carnivore, it avoided competition. The evolution of a large body size granted P. brasiliensis many advantages, but it may also have led to its vulnerability. The constantly changing environment on a large geological scale may have reduced its long-term survival, favoring smaller species more resilient to ecological shifts.

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          The giant crocodyliform Sarcosuchus from the Cretaceous of Africa.

          New fossils of the giant African crocodyliform Sarcosuchus imperator clarify its skeletal anatomy, growth patterns, size, longevity, and phylogenetic position. The skull has an expansive narial bulla and elongate jaws studded with stout, smooth crowns that do not interlock. The jaw form suggests a generalized diet of large vertebrates, including fish and dinosaurs. S. imperator is estimated to have grown to a maximum body length of at least 11 to 12 meters and body weight of about 8 metric tons over a life-span of 50 to 60 years. Unlike its closest relatives, which lived as specialized piscivores in marginal marine habitats, S. imperator thrived in fluvial environments.
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            Bite forces and evolutionary adaptations to feeding ecology in carnivores.

            The Carnivora spans the largest ecological and body size diversity of any mammalian order, making it an ideal basis for studies of evolutionary ecology and functional morphology. For animals with different feeding ecologies, it may be expected that bite force represents an important evolutionary adaptation, but studies have been constrained by a lack of bite force data. In this study we present predictions of bite forces for 151 species of extant carnivores, comprising representatives from all eight families and the entire size and ecological spectrum within the order. We show that, when normalized for body size, bite forces differ significantly between the various feeding categories. At opposing extremes and independent of genealogy, consumers of tough fibrous plant material and carnivores preying on large prey both have high bite forces for their size, while bite force adjusted for body mass is low among specialized insectivores. Omnivores and carnivores preying on small prey have more moderate bite forces for their size. These findings indicate that differences in bite force represent important adaptations to and indicators of differing feeding ecologies throughout carnivoran evolution. Our results suggest that the incorporation of bite force data may assist in the construction of more robust evolutionary and palaeontological analyses of feeding ecology.
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              Size-dependent life-history traits promote catastrophic collapses of top predators.

              Catastrophic population collapses such as observed in many exploited fish populations have been argued to result from depensatory growth mechanisms (i.e., reduced reproductive success at low population densities, also known as Allee effect). Empirical support for depensation from population-level data is, however, hard to obtain and inconclusive. Using a size-structured, individual-based model we show that catastrophic population collapses may nonetheless be an intrinsic property of many communities, because of two general aspects of individual life history: size- and food-dependent individual growth and individual mortality decreasing with body size. Positive density dependence, characteristic for depensatory growth mechanisms and catastrophic behavior, results as a direct and robust consequence of the interplay between these individual life-history traits, which are commonly found in many species.

                Author and article information

                PLoS One
                PLoS ONE
                PLoS ONE
                Public Library of Science (San Francisco, CA USA )
                17 February 2015
                : 10
                : 2
                : e0117944
                [1 ]Departamento de Geologia, Universidade Federal de Pernambuco, CEP 50740-530, Recife, Pernambuco, Brazil
                [2 ]Departamento de Geologia, Universidade Federal do Rio de Janeiro, CEP 21949-900, Rio de Janeiro, Rio de Janeiro, Brazil
                [3 ]Laboratório de Pesquisas Paleontológicas, Universidade Federal do Acre, CEP 69915-900, Rio Branco, Acre, Brazil
                [4 ]Ecoinformatics Studio, P. O. Box 46521, CEP 20551-970, Rio de Janeiro, Rio de Janeiro, Brazil
                [5 ]Instituto de Biologia, Universidade Federal de Uberlândia, CEP 38400-902, Uberlândia, Minas Gerais, Brazil
                Author notes

                Competing Interests: The authors have declared that no competing interests exist.

                Conceived and designed the experiments: TA MJC. Performed the experiments: TA MJC. Analyzed the data: AMG DR. Contributed reagents/materials/analysis tools: JPSF EG. Wrote the paper: TA AMG DF JPSF EG.


                This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

                : 7 March 2014
                : 5 January 2015
                Page count
                Figures: 5, Tables: 3, Pages: 14
                The publication cost was fully funded by FAPEMIG and the Post Graduation Department of UFU. The links are: http://www.fapemig.br/ and http://www.portal.ib.ufu.br/. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
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