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      Cranial bone histology of Metoposaurus krasiejowensis (Amphibia, Temnospondyli) from the Late Triassic of Poland

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      PeerJ
      PeerJ Inc.
      Skull, Dermal bones, Microanatomy, Growth pattern

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          Abstract

          In this study, 21 skull bones of Metoposaurus krasiejowensis from the Late Triassic of Poland were investigated histologically. Dermal bones show a diploë structure, with an ornamented external surface. The ridges consist of mostly well vascularized parallel-fibered bone; the valleys are built of an avascular layer of lamellar bone. The thick middle region consists of cancellous bone, with varying porosity. The thin and less vascularized internal cortex consists of parallel-fibered bone. The numerous Sharpey’s fibers and ISF are present in all bones. The cyclicity of growth is manifested as an alternation of thick, avascular annuli and high vascularized zones as well as a sequence of resting lines. The detailed histological framework of dermal bones varies even within a single bone; this seems to be related to the local biomechanical loading of the particular part of the skull. The dynamic processes observed during the ornamentation creation indicate that the positions of the ridges and grooves change during growth and could be a specific adaptation to changing biomechanical conditions and stress distribution during bone development. In the supratemporal, the cementing lines show that the remodeling process could be involved in the creations of sculpture. The common occurrence of ISF suggests that metaplastic ossification plays an important role during cranial development. Endochondral bones preserved the numerous remains of calcified cartilage. This indicates that ossification follows a pattern known for stereospondyl intercentra, with relatively slow ossification of the trabecular part and late development of the periosteal cortex. The large accumulation of Sharpey’s fibers in the occipital condyles indicates the presence of strong muscles and ligaments connecting the skull to the vertebral column.

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          A beaked herbivorous archosaur with dinosaur affinities from the early Late Triassic of Poland

          Jerzy Dzik (2003)
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            Longbone histology of the Tendaguru sauropods: implications for growth and biology

            P. Sander (2000)
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              Assessing dinosaur growth patterns: a microscopic revolution.

              Some of the longest standing questions in dinosaur paleontology pertain to their development. Did dinosaurs grow at slow rates similar to extant reptiles or rapidly similar to living birds and mammals? How did some forms attain gigantic proportions? Conversely, how did birds (avian dinosaurs) become miniaturized? New data on dinosaur longevity garnered from bone microstructure (i.e. osteohistology) are making it possible to assess basic life-history parameters of the dinosaurs such as growth rates and timing of developmental events. Analyses of these data in an evolutionary context are enabling the identification of developmental patterns that lead to size changes within the Dinosauria. Furthermore, this rich new database is providing inroads for studying individual and population biology. All in all, paleohistological research is proving to be the most promising avenue towards gaining a comprehensive understanding of dinosaur biology.
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                Author and article information

                Contributors
                Journal
                PeerJ
                PeerJ
                peerj
                peerj
                PeerJ
                PeerJ Inc. (San Francisco, USA )
                2167-8359
                8 November 2016
                2016
                : 4
                : e2685
                Affiliations
                [1 ]Department of Biosystematics, University of Opole , Opole, Poland
                [2 ]European Centre of Palaeontology, University of Opole , Opole, Poland
                [3 ]Steinmann Institute, University of Bonn , Bonn, Germany
                Article
                2685
                10.7717/peerj.2685
                5103832
                47946056-2f78-4ac3-afe9-ae5fee544739
                ©2016 Gruntmejer et al.

                This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ) and either DOI or URL of the article must be cited.

                History
                : 7 April 2016
                : 13 October 2016
                Funding
                The authors received no funding for this work.
                Categories
                Paleontology
                Histology

                skull,dermal bones,microanatomy,growth pattern
                skull, dermal bones, microanatomy, growth pattern

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