The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform
Emily J. Rayfield - One of the best experts on this subject based on the ideXlab platform.
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Validation experiments on finite element models of an ostrich (Struthio camelus) cranium.
PeerJ, 2015Co-Authors: Andrew R. Cuff, Jen A. Bright, Emily J. RayfieldAbstract:The first finite element (FE) validation of a complete avian cranium was performed on an extant palaeognath, the ostrich (Struthio camelus). Ex-vivo strains were collected from the cranial bone and Rhamphotheca. These experimental strains were then compared to convergence tested, specimen-specific finite element (FE) models. The FE models contained segmented cortical and trabecular bone, sutures and the keratinous Rhamphotheca as identified from micro-CT scan data. Each of these individual materials was assigned isotropic material properties either from the literature or from nanoindentation, and the FE models compared to the ex-vivo results. The FE models generally replicate the location of peak strains and reflect the correct mode of deformation in the rostral region. The models are too stiff in regions of experimentally recorded high strain and too elastic in regions of low experimentally recorded low strain. The mode of deformation in the low strain neurocranial region is not replicated by the FE models, and although the models replicate strain orientations to within 10° in some regions, in most regions the correlation is not strong. Cranial sutures, as has previously been found in other taxa, are important for modifying both strain magnitude and strain patterns across the entire skull, but especially between opposing the sutural junctions. Experimentally, we find that the strains on the surface of the Rhamphotheca are much lower than those found on nearby bone. The FE models produce much higher principal strains despite similar strain ratios across the entirety of the Rhamphotheca. This study emphasises the importance of attempting to validate FE models, modelling sutures and Rhamphothecae in birds, and shows that whilst location of peak strain and patterns of deformation can be modelled, replicating experimental data in digital models of avian crania remains problematic.
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Retrodeformation and muscular reconstruction of ornithomimosaurian dinosaur crania
PeerJ, 2015Co-Authors: Andrew R. Cuff, Emily J. RayfieldAbstract:Ornithomimosaur dinosaurs evolved lightweight, edentulous skulls that possessed keratinous Rhamphothecae. Understanding the anatomy of these taxa allows for a greater understanding of “ostrich-mimic” dinosaurs and character change during theropod dinosaur evolution. However, taphonomic processes during fossilisation often distort fossil remains. Retrodeformation offers a means by which to recover a hypothesis of the original anatomy of the specimen, and 3D scanning technologies present a way to constrain and document the retrodeformation process. Using computed tomography (CT) scan data, specimen specific retrodeformations were performed on three-dimensionally preserved but taphonomically distorted skulls of the deinocheirid Garudimimus brevipes Barsbold, 1981 and the ornithomimids Struthiomimus altus Lambe, 1902 and Ornithomimus edmontonicus Sternberg, 1933. This allowed for a reconstruction of the adductor musculature, which was then mapped onto the crania, from which muscle mechanical advantage and bite forces were calculated pre- and post-retrodeformation. The extent of the Rhamphotheca was varied in each taxon to represent morphologies found within modern Aves. Well constrained retrodeformation allows for increased confidence in anatomical and functional analysis of fossil specimens and offers an opportunity to more fully understand the soft tissue anatomy of extinct taxa.
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Cranial anatomy of Erlikosaurus andrewsi (Dinosauria, Therizinosauria): New insights based on digital reconstruction
Journal of Vertebrate Paleontology, 2014Co-Authors: Stephan Lautenschlager, Lawrence M Witmer, Perle Altangerel, Lindsay E. Zanno, Emily J. RayfieldAbstract:ABSTRACTThe skull of Erlikosaurus andrewsi from the Upper Cretaceous Baishin Tsav locality of Mongolia represents the only known three-dimensionally preserved and nearly complete skull of a therizinosaurian. Computed tomographic (CT) scanning of the original specimen and three-dimensional visualization techniques allow the cranial skeleton to be digitally prepared, disarticulated, and restored. Here, we present a detailed description of the restored skull morphology and the individual cranial elements, including visualization of the internal neurovascular and pneumatic structures. Information gained from this study is used in a revised and emended diagnosis for E. andrewsi. A reappraisal of the evolutionary and functional changes in the cranial skeleton as provided by this study supports prior proposals that a keratinous sheath or Rhamphotheca was developed early in the evolution of Therizinosauria. Paralleled by the reduction of functional and replacement teeth, this development indicates a shift in the ...
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Cranial anatomy of Erlikosaurus andrewsi (Dinosauria, Therizinosauria): new insights based on digital reconstruction
2014Co-Authors: Stephan Lautenschlager, Lawrence M Witmer, Perle Altangerel, Lindsay E. Zanno, Emily J. RayfieldAbstract:ABSTRACTThe skull of Erlikosaurus andrewsi from the Upper Cretaceous Baishin Tsav locality of Mongolia represents the only known three-dimensionally preserved and nearly complete skull of a therizinosaurian. Computed tomographic (CT) scanning of the original specimen and three-dimensional visualization techniques allow the cranial skeleton to be digitally prepared, disarticulated, and restored. Here, we present a detailed description of the restored skull morphology and the individual cranial elements, including visualization of the internal neurovascular and pneumatic structures. Information gained from this study is used in a revised and emended diagnosis for E. andrewsi. A reappraisal of the evolutionary and functional changes in the cranial skeleton as provided by this study supports prior proposals that a keratinous sheath or Rhamphotheca was developed early in the evolution of Therizinosauria. Paralleled by the reduction of functional and replacement teeth, this development indicates a shift in the manner of food processing/procurement at the tip of the snout. Extensive pneumatization of the braincase, most evidently developed in E. andrewsi in comparison with other known therizinosaurians, appears to have led to a reduction of the adductor musculature and thus the potential bite force in derived therizinosaurians. In addition, the application of digital data, as presented in this study, introduces a novel way to document fossil data that will allow for morphological and anatomical data to be made widely accessible.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP
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edentulism beaks and biomechanical innovations in the evolution of theropod dinosaurs
Proceedings of the National Academy of Sciences of the United States of America, 2013Co-Authors: Stephan Lautenschlager, Lawrence M Witmer, Perle Altangerel, Emily J. RayfieldAbstract:Maniraptoriformes, the speciose group of derived theropod dinosaurs that ultimately gave rise to modern birds, display a diverse and remarkable suite of skeletal adaptations. Apart from the evolution of flight, a large-scale change in dietary behavior appears to have been one of the main triggers for specializations in the bauplan of these derived theropods. Among the different skeletal specializations, partial or even complete edentulism and the development of keratinous beaks form a recurring and persistent trend in from the evolution of derived nonavian dinosaurs. Therizinosauria is an enigmatic maniraptoriform clade, whose members display these and other osteological characters thought to be correlated with the shift from carnivory to herbivory. This makes therizinosaurians prime candidates to assess the functional significance of these morphological characters. Based on a highly detailed biomechanical model of Erlikosaurus andrewsi, a therizinosaurid from the Upper Cretaceous of Mongolia, different morphological configurations incorporating soft-tissue structures, such as a keratinous Rhamphotheca, are evaluated for their biomechanical performance. Our results indicate that the development of beaks and the presence of a keratinous Rhamphotheca would have helped to dissipate stress and strain, making the rostral part of the skull less susceptible to bending and displacement, and this benefit may extend to other vertebrate clades that possess Rhamphothecae. Keratinous beaks, paralleled by edentulism, thus represent an evolutionary innovation developed early in derived theropods to enhance cranial stability, distinct to postulated mass-saving benefits associated with the origin of flight.
Stephan Lautenschlager - One of the best experts on this subject based on the ideXlab platform.
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Cranial anatomy of Erlikosaurus andrewsi (Dinosauria, Therizinosauria): New insights based on digital reconstruction
Journal of Vertebrate Paleontology, 2014Co-Authors: Stephan Lautenschlager, Lawrence M Witmer, Perle Altangerel, Lindsay E. Zanno, Emily J. RayfieldAbstract:ABSTRACTThe skull of Erlikosaurus andrewsi from the Upper Cretaceous Baishin Tsav locality of Mongolia represents the only known three-dimensionally preserved and nearly complete skull of a therizinosaurian. Computed tomographic (CT) scanning of the original specimen and three-dimensional visualization techniques allow the cranial skeleton to be digitally prepared, disarticulated, and restored. Here, we present a detailed description of the restored skull morphology and the individual cranial elements, including visualization of the internal neurovascular and pneumatic structures. Information gained from this study is used in a revised and emended diagnosis for E. andrewsi. A reappraisal of the evolutionary and functional changes in the cranial skeleton as provided by this study supports prior proposals that a keratinous sheath or Rhamphotheca was developed early in the evolution of Therizinosauria. Paralleled by the reduction of functional and replacement teeth, this development indicates a shift in the ...
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Cranial anatomy of Erlikosaurus andrewsi (Dinosauria, Therizinosauria): new insights based on digital reconstruction
2014Co-Authors: Stephan Lautenschlager, Lawrence M Witmer, Perle Altangerel, Lindsay E. Zanno, Emily J. RayfieldAbstract:ABSTRACTThe skull of Erlikosaurus andrewsi from the Upper Cretaceous Baishin Tsav locality of Mongolia represents the only known three-dimensionally preserved and nearly complete skull of a therizinosaurian. Computed tomographic (CT) scanning of the original specimen and three-dimensional visualization techniques allow the cranial skeleton to be digitally prepared, disarticulated, and restored. Here, we present a detailed description of the restored skull morphology and the individual cranial elements, including visualization of the internal neurovascular and pneumatic structures. Information gained from this study is used in a revised and emended diagnosis for E. andrewsi. A reappraisal of the evolutionary and functional changes in the cranial skeleton as provided by this study supports prior proposals that a keratinous sheath or Rhamphotheca was developed early in the evolution of Therizinosauria. Paralleled by the reduction of functional and replacement teeth, this development indicates a shift in the manner of food processing/procurement at the tip of the snout. Extensive pneumatization of the braincase, most evidently developed in E. andrewsi in comparison with other known therizinosaurians, appears to have led to a reduction of the adductor musculature and thus the potential bite force in derived therizinosaurians. In addition, the application of digital data, as presented in this study, introduces a novel way to document fossil data that will allow for morphological and anatomical data to be made widely accessible.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP
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edentulism beaks and biomechanical innovations in the evolution of theropod dinosaurs
Proceedings of the National Academy of Sciences of the United States of America, 2013Co-Authors: Stephan Lautenschlager, Lawrence M Witmer, Perle Altangerel, Emily J. RayfieldAbstract:Maniraptoriformes, the speciose group of derived theropod dinosaurs that ultimately gave rise to modern birds, display a diverse and remarkable suite of skeletal adaptations. Apart from the evolution of flight, a large-scale change in dietary behavior appears to have been one of the main triggers for specializations in the bauplan of these derived theropods. Among the different skeletal specializations, partial or even complete edentulism and the development of keratinous beaks form a recurring and persistent trend in from the evolution of derived nonavian dinosaurs. Therizinosauria is an enigmatic maniraptoriform clade, whose members display these and other osteological characters thought to be correlated with the shift from carnivory to herbivory. This makes therizinosaurians prime candidates to assess the functional significance of these morphological characters. Based on a highly detailed biomechanical model of Erlikosaurus andrewsi, a therizinosaurid from the Upper Cretaceous of Mongolia, different morphological configurations incorporating soft-tissue structures, such as a keratinous Rhamphotheca, are evaluated for their biomechanical performance. Our results indicate that the development of beaks and the presence of a keratinous Rhamphotheca would have helped to dissipate stress and strain, making the rostral part of the skull less susceptible to bending and displacement, and this benefit may extend to other vertebrate clades that possess Rhamphothecae. Keratinous beaks, paralleled by edentulism, thus represent an evolutionary innovation developed early in derived theropods to enhance cranial stability, distinct to postulated mass-saving benefits associated with the origin of flight.
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The endocranial anatomy of therizinosauria and its implications for sensory and cognitive function.
PloS one, 2012Co-Authors: Stephan Lautenschlager, Emily J. Rayfield, Perle Altangerel, Lindsay E. Zanno, Lawrence M WitmerAbstract:Background: Therizinosauria is one of the most enigmatic and peculiar clades among theropod dinosaurs, exhibiting an unusual suite of characters, such as lanceolate teeth, a rostral Rhamphotheca, long manual claws, and a wide, opisthopubic pelvis. This specialized anatomy has been associated with a shift in dietary preferences and an adaptation to herbivory. Despite a large number of discoveries in recent years, the fossil record for Therizinosauria is still relatively poor, and cranial remains are particularly rare. Methodology/Principal Findings: Based on computed tomographic (CT) scanning of the nearly complete and articulated skull of Erlikosaurus andrewsi, as well as partial braincases of two other therizinosaurian taxa, the endocranial anatomy is reconstructed and described. The wider phylogenetic range of the described specimens permits the evaluation of sensory and cognitive capabilities of Therizinosauria in an evolutionary context. The endocranial anatomy reveals a mosaic of plesiomorphic and derived characters in therizinosaurians. The anatomy of the olfactory apparatus and the endosseous labyrinth suggests that olfaction, hearing, and equilibrium were well-developed in therizinosaurians and might have affected or benefited from an enlarged telencephalon. Conclusion/Significance: This study presents the first appraisal of the evolution of endocranial anatomy and sensory adaptations in Therizinosauria. Despite their phylogenetically basal position among maniraptoran dinosaurs, therizinosaurians had developed the neural pathways for a well developed sensory repertoire. In particular olfaction and hearing may have played an important role in foraging, predator evasion, and/or social complexity.
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The endocranial anatomy of Therizinosauria and its implications for sensory and cognitive function
2012Co-Authors: Stephan Lautenschlager, Emily J. Rayfield, Perle Altangerel, Lindsay E. Zanno, Lawrence M WitmerAbstract:Background: Therizinosauria is one of the most enigmatic and peculiar clades among theropod dinosaurs, exhibiting an unusual suite of characters, such as lanceolate teeth, a rostral Rhamphotheca, long manual claws, and a wide, opisthopubic pelvis. This specialized anatomy has been associated with a shift in dietary preferences and an adaptation to herbivory. Despite a large number of discoveries in recent years, the fossil record for Therizinosauria is still relatively poor, and cranial remains are particularly rare. Methodology/Principal Findings: Based on computed tomographic (CT) scanning of the nearly complete and articulated skull of Erlikosaurus andrewsi, as well as partial braincases of two other therizinosaurian taxa, the endocranial anatomy is reconstructed and described. The wider phylogenetic range of the described specimens permits the evaluation of sensory and cognitive capabilities of Therizinosauria in an evolutionary context. The endocranial anatomy reveals a mosaic of plesiomorphic and derived characters in therizinosaurians. The anatomy of the olfactory apparatus and the endosseous labyrinth suggests that olfaction, hearing, and equilibrium were well-developed in therizinosaurians and might have affected or benefited from an enlarged telencephalon. Conclusion/Significance: This study presents the first appraisal of the evolution of endocranial anatomy and sensory adaptations in Therizinosauria. Despite their phylogenetically basal position among maniraptoran dinosaurs, therizinosaur
Lawrence M Witmer - One of the best experts on this subject based on the ideXlab platform.
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Cranial anatomy of Erlikosaurus andrewsi (Dinosauria, Therizinosauria): New insights based on digital reconstruction
Journal of Vertebrate Paleontology, 2014Co-Authors: Stephan Lautenschlager, Lawrence M Witmer, Perle Altangerel, Lindsay E. Zanno, Emily J. RayfieldAbstract:ABSTRACTThe skull of Erlikosaurus andrewsi from the Upper Cretaceous Baishin Tsav locality of Mongolia represents the only known three-dimensionally preserved and nearly complete skull of a therizinosaurian. Computed tomographic (CT) scanning of the original specimen and three-dimensional visualization techniques allow the cranial skeleton to be digitally prepared, disarticulated, and restored. Here, we present a detailed description of the restored skull morphology and the individual cranial elements, including visualization of the internal neurovascular and pneumatic structures. Information gained from this study is used in a revised and emended diagnosis for E. andrewsi. A reappraisal of the evolutionary and functional changes in the cranial skeleton as provided by this study supports prior proposals that a keratinous sheath or Rhamphotheca was developed early in the evolution of Therizinosauria. Paralleled by the reduction of functional and replacement teeth, this development indicates a shift in the ...
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Cranial anatomy of Erlikosaurus andrewsi (Dinosauria, Therizinosauria): new insights based on digital reconstruction
2014Co-Authors: Stephan Lautenschlager, Lawrence M Witmer, Perle Altangerel, Lindsay E. Zanno, Emily J. RayfieldAbstract:ABSTRACTThe skull of Erlikosaurus andrewsi from the Upper Cretaceous Baishin Tsav locality of Mongolia represents the only known three-dimensionally preserved and nearly complete skull of a therizinosaurian. Computed tomographic (CT) scanning of the original specimen and three-dimensional visualization techniques allow the cranial skeleton to be digitally prepared, disarticulated, and restored. Here, we present a detailed description of the restored skull morphology and the individual cranial elements, including visualization of the internal neurovascular and pneumatic structures. Information gained from this study is used in a revised and emended diagnosis for E. andrewsi. A reappraisal of the evolutionary and functional changes in the cranial skeleton as provided by this study supports prior proposals that a keratinous sheath or Rhamphotheca was developed early in the evolution of Therizinosauria. Paralleled by the reduction of functional and replacement teeth, this development indicates a shift in the manner of food processing/procurement at the tip of the snout. Extensive pneumatization of the braincase, most evidently developed in E. andrewsi in comparison with other known therizinosaurians, appears to have led to a reduction of the adductor musculature and thus the potential bite force in derived therizinosaurians. In addition, the application of digital data, as presented in this study, introduces a novel way to document fossil data that will allow for morphological and anatomical data to be made widely accessible.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP
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edentulism beaks and biomechanical innovations in the evolution of theropod dinosaurs
Proceedings of the National Academy of Sciences of the United States of America, 2013Co-Authors: Stephan Lautenschlager, Lawrence M Witmer, Perle Altangerel, Emily J. RayfieldAbstract:Maniraptoriformes, the speciose group of derived theropod dinosaurs that ultimately gave rise to modern birds, display a diverse and remarkable suite of skeletal adaptations. Apart from the evolution of flight, a large-scale change in dietary behavior appears to have been one of the main triggers for specializations in the bauplan of these derived theropods. Among the different skeletal specializations, partial or even complete edentulism and the development of keratinous beaks form a recurring and persistent trend in from the evolution of derived nonavian dinosaurs. Therizinosauria is an enigmatic maniraptoriform clade, whose members display these and other osteological characters thought to be correlated with the shift from carnivory to herbivory. This makes therizinosaurians prime candidates to assess the functional significance of these morphological characters. Based on a highly detailed biomechanical model of Erlikosaurus andrewsi, a therizinosaurid from the Upper Cretaceous of Mongolia, different morphological configurations incorporating soft-tissue structures, such as a keratinous Rhamphotheca, are evaluated for their biomechanical performance. Our results indicate that the development of beaks and the presence of a keratinous Rhamphotheca would have helped to dissipate stress and strain, making the rostral part of the skull less susceptible to bending and displacement, and this benefit may extend to other vertebrate clades that possess Rhamphothecae. Keratinous beaks, paralleled by edentulism, thus represent an evolutionary innovation developed early in derived theropods to enhance cranial stability, distinct to postulated mass-saving benefits associated with the origin of flight.
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The endocranial anatomy of therizinosauria and its implications for sensory and cognitive function.
PloS one, 2012Co-Authors: Stephan Lautenschlager, Emily J. Rayfield, Perle Altangerel, Lindsay E. Zanno, Lawrence M WitmerAbstract:Background: Therizinosauria is one of the most enigmatic and peculiar clades among theropod dinosaurs, exhibiting an unusual suite of characters, such as lanceolate teeth, a rostral Rhamphotheca, long manual claws, and a wide, opisthopubic pelvis. This specialized anatomy has been associated with a shift in dietary preferences and an adaptation to herbivory. Despite a large number of discoveries in recent years, the fossil record for Therizinosauria is still relatively poor, and cranial remains are particularly rare. Methodology/Principal Findings: Based on computed tomographic (CT) scanning of the nearly complete and articulated skull of Erlikosaurus andrewsi, as well as partial braincases of two other therizinosaurian taxa, the endocranial anatomy is reconstructed and described. The wider phylogenetic range of the described specimens permits the evaluation of sensory and cognitive capabilities of Therizinosauria in an evolutionary context. The endocranial anatomy reveals a mosaic of plesiomorphic and derived characters in therizinosaurians. The anatomy of the olfactory apparatus and the endosseous labyrinth suggests that olfaction, hearing, and equilibrium were well-developed in therizinosaurians and might have affected or benefited from an enlarged telencephalon. Conclusion/Significance: This study presents the first appraisal of the evolution of endocranial anatomy and sensory adaptations in Therizinosauria. Despite their phylogenetically basal position among maniraptoran dinosaurs, therizinosaurians had developed the neural pathways for a well developed sensory repertoire. In particular olfaction and hearing may have played an important role in foraging, predator evasion, and/or social complexity.
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The endocranial anatomy of Therizinosauria and its implications for sensory and cognitive function
2012Co-Authors: Stephan Lautenschlager, Emily J. Rayfield, Perle Altangerel, Lindsay E. Zanno, Lawrence M WitmerAbstract:Background: Therizinosauria is one of the most enigmatic and peculiar clades among theropod dinosaurs, exhibiting an unusual suite of characters, such as lanceolate teeth, a rostral Rhamphotheca, long manual claws, and a wide, opisthopubic pelvis. This specialized anatomy has been associated with a shift in dietary preferences and an adaptation to herbivory. Despite a large number of discoveries in recent years, the fossil record for Therizinosauria is still relatively poor, and cranial remains are particularly rare. Methodology/Principal Findings: Based on computed tomographic (CT) scanning of the nearly complete and articulated skull of Erlikosaurus andrewsi, as well as partial braincases of two other therizinosaurian taxa, the endocranial anatomy is reconstructed and described. The wider phylogenetic range of the described specimens permits the evaluation of sensory and cognitive capabilities of Therizinosauria in an evolutionary context. The endocranial anatomy reveals a mosaic of plesiomorphic and derived characters in therizinosaurians. The anatomy of the olfactory apparatus and the endosseous labyrinth suggests that olfaction, hearing, and equilibrium were well-developed in therizinosaurians and might have affected or benefited from an enlarged telencephalon. Conclusion/Significance: This study presents the first appraisal of the evolution of endocranial anatomy and sensory adaptations in Therizinosauria. Despite their phylogenetically basal position among maniraptoran dinosaurs, therizinosaur
Perle Altangerel - One of the best experts on this subject based on the ideXlab platform.
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Cranial anatomy of Erlikosaurus andrewsi (Dinosauria, Therizinosauria): New insights based on digital reconstruction
Journal of Vertebrate Paleontology, 2014Co-Authors: Stephan Lautenschlager, Lawrence M Witmer, Perle Altangerel, Lindsay E. Zanno, Emily J. RayfieldAbstract:ABSTRACTThe skull of Erlikosaurus andrewsi from the Upper Cretaceous Baishin Tsav locality of Mongolia represents the only known three-dimensionally preserved and nearly complete skull of a therizinosaurian. Computed tomographic (CT) scanning of the original specimen and three-dimensional visualization techniques allow the cranial skeleton to be digitally prepared, disarticulated, and restored. Here, we present a detailed description of the restored skull morphology and the individual cranial elements, including visualization of the internal neurovascular and pneumatic structures. Information gained from this study is used in a revised and emended diagnosis for E. andrewsi. A reappraisal of the evolutionary and functional changes in the cranial skeleton as provided by this study supports prior proposals that a keratinous sheath or Rhamphotheca was developed early in the evolution of Therizinosauria. Paralleled by the reduction of functional and replacement teeth, this development indicates a shift in the ...
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Cranial anatomy of Erlikosaurus andrewsi (Dinosauria, Therizinosauria): new insights based on digital reconstruction
2014Co-Authors: Stephan Lautenschlager, Lawrence M Witmer, Perle Altangerel, Lindsay E. Zanno, Emily J. RayfieldAbstract:ABSTRACTThe skull of Erlikosaurus andrewsi from the Upper Cretaceous Baishin Tsav locality of Mongolia represents the only known three-dimensionally preserved and nearly complete skull of a therizinosaurian. Computed tomographic (CT) scanning of the original specimen and three-dimensional visualization techniques allow the cranial skeleton to be digitally prepared, disarticulated, and restored. Here, we present a detailed description of the restored skull morphology and the individual cranial elements, including visualization of the internal neurovascular and pneumatic structures. Information gained from this study is used in a revised and emended diagnosis for E. andrewsi. A reappraisal of the evolutionary and functional changes in the cranial skeleton as provided by this study supports prior proposals that a keratinous sheath or Rhamphotheca was developed early in the evolution of Therizinosauria. Paralleled by the reduction of functional and replacement teeth, this development indicates a shift in the manner of food processing/procurement at the tip of the snout. Extensive pneumatization of the braincase, most evidently developed in E. andrewsi in comparison with other known therizinosaurians, appears to have led to a reduction of the adductor musculature and thus the potential bite force in derived therizinosaurians. In addition, the application of digital data, as presented in this study, introduces a novel way to document fossil data that will allow for morphological and anatomical data to be made widely accessible.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP
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edentulism beaks and biomechanical innovations in the evolution of theropod dinosaurs
Proceedings of the National Academy of Sciences of the United States of America, 2013Co-Authors: Stephan Lautenschlager, Lawrence M Witmer, Perle Altangerel, Emily J. RayfieldAbstract:Maniraptoriformes, the speciose group of derived theropod dinosaurs that ultimately gave rise to modern birds, display a diverse and remarkable suite of skeletal adaptations. Apart from the evolution of flight, a large-scale change in dietary behavior appears to have been one of the main triggers for specializations in the bauplan of these derived theropods. Among the different skeletal specializations, partial or even complete edentulism and the development of keratinous beaks form a recurring and persistent trend in from the evolution of derived nonavian dinosaurs. Therizinosauria is an enigmatic maniraptoriform clade, whose members display these and other osteological characters thought to be correlated with the shift from carnivory to herbivory. This makes therizinosaurians prime candidates to assess the functional significance of these morphological characters. Based on a highly detailed biomechanical model of Erlikosaurus andrewsi, a therizinosaurid from the Upper Cretaceous of Mongolia, different morphological configurations incorporating soft-tissue structures, such as a keratinous Rhamphotheca, are evaluated for their biomechanical performance. Our results indicate that the development of beaks and the presence of a keratinous Rhamphotheca would have helped to dissipate stress and strain, making the rostral part of the skull less susceptible to bending and displacement, and this benefit may extend to other vertebrate clades that possess Rhamphothecae. Keratinous beaks, paralleled by edentulism, thus represent an evolutionary innovation developed early in derived theropods to enhance cranial stability, distinct to postulated mass-saving benefits associated with the origin of flight.
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The endocranial anatomy of therizinosauria and its implications for sensory and cognitive function.
PloS one, 2012Co-Authors: Stephan Lautenschlager, Emily J. Rayfield, Perle Altangerel, Lindsay E. Zanno, Lawrence M WitmerAbstract:Background: Therizinosauria is one of the most enigmatic and peculiar clades among theropod dinosaurs, exhibiting an unusual suite of characters, such as lanceolate teeth, a rostral Rhamphotheca, long manual claws, and a wide, opisthopubic pelvis. This specialized anatomy has been associated with a shift in dietary preferences and an adaptation to herbivory. Despite a large number of discoveries in recent years, the fossil record for Therizinosauria is still relatively poor, and cranial remains are particularly rare. Methodology/Principal Findings: Based on computed tomographic (CT) scanning of the nearly complete and articulated skull of Erlikosaurus andrewsi, as well as partial braincases of two other therizinosaurian taxa, the endocranial anatomy is reconstructed and described. The wider phylogenetic range of the described specimens permits the evaluation of sensory and cognitive capabilities of Therizinosauria in an evolutionary context. The endocranial anatomy reveals a mosaic of plesiomorphic and derived characters in therizinosaurians. The anatomy of the olfactory apparatus and the endosseous labyrinth suggests that olfaction, hearing, and equilibrium were well-developed in therizinosaurians and might have affected or benefited from an enlarged telencephalon. Conclusion/Significance: This study presents the first appraisal of the evolution of endocranial anatomy and sensory adaptations in Therizinosauria. Despite their phylogenetically basal position among maniraptoran dinosaurs, therizinosaurians had developed the neural pathways for a well developed sensory repertoire. In particular olfaction and hearing may have played an important role in foraging, predator evasion, and/or social complexity.
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The endocranial anatomy of Therizinosauria and its implications for sensory and cognitive function
2012Co-Authors: Stephan Lautenschlager, Emily J. Rayfield, Perle Altangerel, Lindsay E. Zanno, Lawrence M WitmerAbstract:Background: Therizinosauria is one of the most enigmatic and peculiar clades among theropod dinosaurs, exhibiting an unusual suite of characters, such as lanceolate teeth, a rostral Rhamphotheca, long manual claws, and a wide, opisthopubic pelvis. This specialized anatomy has been associated with a shift in dietary preferences and an adaptation to herbivory. Despite a large number of discoveries in recent years, the fossil record for Therizinosauria is still relatively poor, and cranial remains are particularly rare. Methodology/Principal Findings: Based on computed tomographic (CT) scanning of the nearly complete and articulated skull of Erlikosaurus andrewsi, as well as partial braincases of two other therizinosaurian taxa, the endocranial anatomy is reconstructed and described. The wider phylogenetic range of the described specimens permits the evaluation of sensory and cognitive capabilities of Therizinosauria in an evolutionary context. The endocranial anatomy reveals a mosaic of plesiomorphic and derived characters in therizinosaurians. The anatomy of the olfactory apparatus and the endosseous labyrinth suggests that olfaction, hearing, and equilibrium were well-developed in therizinosaurians and might have affected or benefited from an enlarged telencephalon. Conclusion/Significance: This study presents the first appraisal of the evolution of endocranial anatomy and sensory adaptations in Therizinosauria. Despite their phylogenetically basal position among maniraptoran dinosaurs, therizinosaur
Marc A. Meyers - One of the best experts on this subject based on the ideXlab platform.
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Mechanical behavior of prosthesis in Toucan beak (Ramphastos toco)
Materials Science and Engineering: C, 2010Co-Authors: Roberto Silveira Fecchio, Yasuaki Seki, Sara Bodde, M.s. Gomes, J. Kolososki, João Luiz Rossi, Marco Antonio Gioso, Marc A. MeyersAbstract:article i nfo The purpose of this study is to characterize the structure of the beak of Toco Toucan (Ramphastos toco) and to investigate means for arresting fractures in the rhinotheca using acrylic resin. The structure of the rhamphastid bill has been described as a sandwich structured composite having a thin exterior comprised of keratin and a thick foam core constructed of mineralized collagenous rods (trabeculae). The keratinous Rhamphotheca consists of superposed polygonal scales (approximately 50 µm in diameter and 1 µm in thickness). In order to simulate the orientation of loading to which the beak is subjected during exertion of bite force, for example, we conducted flexure tests on the dorso-ventral axis of the maxilla. The initially intact (without induced fracture) beak fractured in the central portion when subjected to a force of 270 N, at a displacement of 23 mm. The location of this fracture served as a reference for the fractures induced in other beaks tested. The second beak was fractured and repaired by applying resin on both lateral surfaces. The repaired maxilla sustained a force of 70 N with 6.5 mm deflection. The third maxilla was repaired similarly except that it was conditioned in acid for 60s prior to fixation with resin. It resisted a force of up to 63 N at 6m m of deflection. The experimental results were compared with finite element calculations for unfractured beak in bending configuration. The repaired specimens were found to have strength equal to only one third of the intact beak. Finite element simulations allow visualization of how the beak system (sandwich shell and cellular core) sustains high flexural strength.
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Toucan and hornbill beaks: a comparative study.
Acta biomaterialia, 2009Co-Authors: Yasuaki Seki, Sara Bodde, Marc A. MeyersAbstract:Abstract The structure and mechanical behavior of Toco Toucan ( Ramphastos toco ) and Wreathed Hornbill ( Rhyticeros undulatus ) beaks were compared. The beak of both species is a sandwich-structured composite, having an exterior, or Rhamphotheca, consisting of multiple layers of keratin scales and a core composed of a fibrous network of bony closed-cell foam. The Rhamphotheca is an arrangement of ∼50 μm diameter, overlapping, keratin tiles. The hornbill Rhamphotheca exhibits a surface morphology on the ridged casque that is distinguishable from that observed on the bill proper. Intermediate filaments in the keratin matrix were observed by transmission electron microscopy. The Young’s modulus measurements of toucan Rhamphotheca indicate isotropy in longitudinal and transverse directions, whereas those of hornbill Rhamphotheca may suggest anisotropy. The compressive response of beak foam is governed by brittle crushing behavior. The crushing strength of hornbill foam is six times higher than that of toucan foam. Micro- and nanoindentation hardness values were measured for Rhamphotheca and foam trabeculae of toucan and hornbill specimens. The sandwich design of beaks was analyzed using the Karam–Gibson and Dawson–Gibson models. The presence of a cellular core increases the bending resistance (Brazier moment) by a factor of 3–6 while decreasing the compressive strength by only 50%.