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Laaß M, Kaestner A. Nasal turbinates of the dicynodont Kawingasaurus fossilis and the possible impact of the fossorial habitat on the evolution of endothermy. J Morphol 2023; 284:e21621. [PMID: 37585231 DOI: 10.1002/jmor.21621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2022] [Revised: 06/28/2023] [Accepted: 06/29/2023] [Indexed: 08/17/2023]
Abstract
The nasal region of the fossorial anomodont Kawingasaurus fossilis was virtually reconstructed from neutron-computed tomographic data and compared with the terrestrial species Pristerodon mackayi and other nonmammalian synapsids. The tomography of the Kawingasaurus skull reveals a pattern of maxillo-, naso-, fronto- and ethmoturbinal ridges that strongly resemble the mammalian condition. On both sides of the nasal cavity, remains of scrolled maxilloturbinals were preserved that were still partially articulated with maxilloturbinal ridges. Furthermore, possible remains of the lamina semicircularis as well as fronto- or ethmoturbinals were found. In Kawingasaurus, the maxilloturbinal ridges were longer and stronger than in Pristerodon. Except for the nasoturbinal ridges, no other ridges in the olfactory region and no remains of turbinates were recognized. This supports the hypothesis that naso-, fronto-, ethmo- and maxilloturbinals were a plesiomorphic feature of synapsids, but due to their cartilaginous nature in most taxa were, in almost all cases, not preserved. The well-developed maxilloturbinals in Kawingasaurus were probably an adaptation to hypoxia-induced hyperventilation in the fossorial habitat, maintaining the high oxygen demands of Kawingasaurus' large brain. The surface area of the respiratory turbinates in Kawingasaurus falls into the mammalian range, which suggests that they functioned as a countercurrent exchange system for thermoregulation and conditioning of the respiratory airflow. Our results suggest that the environmental conditions of the fossorial habitat led to specific sensory adaptations, accompanied by a pulse in brain evolution and of endothermy in cistecephalids, ~50 million years before the origin of endothermy in the mammalian stem line. This supports the Nocturnal Bottleneck Theory, in that we found evidence for a similar evolutionary scenario in cistecephalids as proposed for early mammals.
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Affiliation(s)
- Michael Laaß
- Fakultät für Geowissenschaften, Geotechnik und Bergbau, TU Bergakademie Freiberg, Freiberg, Germany
- FRM II and Physics E21, Technische Universität München, Garching, Germany
| | - Anders Kaestner
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, Villigen PSI, Switzerland
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2
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Gaetano LC, Abdala F, Seoane FD, Tartaglione A, Schulz M, Otero A, Leardi JM, Apaldetti C, Krapovickas V, Steimbach E. A new cynodont from the Upper Triassic Los Colorados Formation (Argentina, South America) reveals a novel paleobiogeographic context for mammalian ancestors. Sci Rep 2022; 12:6451. [PMID: 35468982 PMCID: PMC9038739 DOI: 10.1038/s41598-022-10486-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 03/31/2022] [Indexed: 11/09/2022] Open
Abstract
Probainognathia is a derived lineage of cynodonts which encompass Mammalia as their crown-group. The rich record of probainognathians from the Carnian of Argentina contrasts with their Norian representation, with only one named species. Here we describe a new probainognathian, Tessellatia bonapartei gen. et sp. nov., from the Norian Los Colorados Formation of the Ischigualasto-Villa Unión Basin of Argentina. The new taxon, represented by a partial cranium with associated lower jaws, was analyzed through neutron and X-rays micro-tomography (μCT). The high-resolution neutron μCT data allowed the identification of a unique character combination, including features inaccessible through traditional techniques. We constructed the largest phylogenetic data matrix of non-mammalian cynodonts. The new species and its sister taxon, the Brazilian Therioherpeton cargnini, are recovered as probainognathians, closely related to Mammaliamorpha. We conducted the first quantitative paleobiogeographic analysis of non-mammalian cynodonts, focusing in probainognathians. The results indicate that Probainognathia and Mammaliamorpha originated in southwestern Gondwana (in the Brazilian Paraná Basin), which was an important center of diversification during the Triassic. Finally, the Chinese Lufeng Basin is identified as the ancestral area of Mammaliaformes. These new findings, besides adding to the knowledge of the poorly represented Norian cynodonts from the Los Colorados Formation, are significant to improve our understanding of probainognathian diversity, evolution, and paleobiogeographic history.
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Affiliation(s)
- L C Gaetano
- Instituto de Estudios Andinos "Don Pablo Groeber" (IDEAN, UBA-CONICET), C1428EGA, Ciudad Autónoma de Buenos Aires, Argentina. .,Evolutionary Studies Institute, University of the Witwatersrand, WITS, Johannesburg, 2050, South Africa.
| | - F Abdala
- Evolutionary Studies Institute, University of the Witwatersrand, WITS, Johannesburg, 2050, South Africa.,Unidad Ejecutora Lillo, CONICET-Fundación Miguel Lillo, T4000JFE, San Miguel de Tucumán, Argentina
| | - F D Seoane
- Instituto de Estudios Andinos "Don Pablo Groeber" (IDEAN, UBA-CONICET), C1428EGA, Ciudad Autónoma de Buenos Aires, Argentina
| | - A Tartaglione
- Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II), Technische Universität München, 85747, Garching, Germany
| | - M Schulz
- Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II), Technische Universität München, 85747, Garching, Germany
| | - A Otero
- División Paleontología de Vertebrados (Anexo Laboratorios), Facultad de Ciencias Naturales Y Museo, Universidad Nacional de La Plata, B1900AVW, La Plata, Argentina
| | - J M Leardi
- Instituto de Estudios Andinos "Don Pablo Groeber" (IDEAN, UBA-CONICET), C1428EGA, Ciudad Autónoma de Buenos Aires, Argentina.,Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, C1428EGA, Ciudad Autónoma de Buenos Aires, Argentina
| | - C Apaldetti
- Instituto y Museo de Ciencias Naturales, Universidad Nacional de San Juan, J5400DNQ, San Juan, Argentina
| | - V Krapovickas
- Instituto de Estudios Andinos "Don Pablo Groeber" (IDEAN, UBA-CONICET), C1428EGA, Ciudad Autónoma de Buenos Aires, Argentina
| | - E Steimbach
- Instituto de Estudios Andinos "Don Pablo Groeber" (IDEAN, UBA-CONICET), C1428EGA, Ciudad Autónoma de Buenos Aires, Argentina
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Törnquist E, Le Cann S, Tudisco E, Tengattini A, Andò E, Lenoir N, Hektor J, Raina DB, Tägil M, Hall SA, Isaksson H. Dual modality neutron and x-ray tomography for enhanced image analysis of the bone-metal interface. Phys Med Biol 2021; 66. [PMID: 34010812 DOI: 10.1088/1361-6560/ac02d4] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 05/19/2021] [Indexed: 11/11/2022]
Abstract
The bone tissue formed at the contact interface with metallic implants, particularly its 3D microstructure, plays a pivotal role for the structural integrity of implant fixation. X-ray tomography is the classical imaging technique used for accessing microstructural information from bone tissue. However, neutron tomography has shown promise for visualising the immediate bone-metal implant interface, something which is highly challenging with x-rays due to large differences in attenuation between metal and biological tissue causing image artefacts. To highlight and explore the complementary nature of neutron and x-ray tomography, proximal rat tibiae with titanium-based implants were imaged with both modalities. The two techniques were compared in terms of visualisation of different material phases and by comparing the properties of the individual images, such as the contrast-to-noise ratio. After superimposing the images using a dedicated image registration algorithm, the complementarity was further investigated via analysis of the dual modality histogram, joining the neutron and x-ray data. From these joint histograms, peaks with well-defined grey value intervals corresponding to the different material phases observed in the specimens were identified and compared. The results highlight differences in how neutrons and x-rays interact with biological tissues and metallic implants, as well as the benefits of combining both modalities. Future refinement of the joint histogram analysis could improve the segmentation of structures and tissues, and yield novel information about specimen-specific properties such as moisture content.
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Affiliation(s)
- Elin Törnquist
- Department of Biomedical Engineering, Lund University, Lund, Sweden
| | - Sophie Le Cann
- Department of Biomedical Engineering, Lund University, Lund, Sweden.,MSME, CNRS UMR 8208, Univ Paris Est Creteil, Univ Gustave Eiffel, Creteil, France
| | - Erika Tudisco
- Division of Geotechnical Engineering, Lund University, Lund, Sweden
| | - Alessandro Tengattini
- Institut Laue-Langevin (ILL), Grenoble, France.,Univ. Grenoble Alpes, CNRS, Grenoble INP, 3SR, Grenoble, France
| | - Edward Andò
- Univ. Grenoble Alpes, CNRS, Grenoble INP, 3SR, Grenoble, France
| | - Nicolas Lenoir
- Institut Laue-Langevin (ILL), Grenoble, France.,Univ. Grenoble Alpes, CNRS, Grenoble INP, 3SR, Grenoble, France
| | - Johan Hektor
- LUNARC-Centre for Scientific and Technical Computing at Lund University, Lund University, Lund, Sweden
| | - Deepak Bushan Raina
- Orthopaedics, Department of Clinical Sciences, Lund, Lund University, Lund, Sweden
| | - Magnus Tägil
- Orthopaedics, Department of Clinical Sciences, Lund, Lund University, Lund, Sweden
| | - Stephen A Hall
- Division of Solid Mechanics, Lund University, Lund, Sweden.,Lund Institute of Advanced Neutron and X-ray Science (LINXS), Lund, Sweden
| | - Hanna Isaksson
- Department of Biomedical Engineering, Lund University, Lund, Sweden.,Orthopaedics, Department of Clinical Sciences, Lund, Lund University, Lund, Sweden
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Benoit J, Ruf I, Miyamae JA, Fernandez V, Rodrigues PG, Rubidge BS. The Evolution of the Maxillary Canal in Probainognathia (Cynodontia, Synapsida): Reassessment of the Homology of the Infraorbital Foramen in Mammalian Ancestors. J MAMM EVOL 2019. [DOI: 10.1007/s10914-019-09467-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Benoit J, Angielczyk KD, Miyamae JA, Manger P, Fernandez V, Rubidge B. Evolution of facial innervation in anomodont therapsids (Synapsida): Insights from X-ray computerized microtomography. J Morphol 2018; 279:673-701. [PMID: 29464761 DOI: 10.1002/jmor.20804] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 01/29/2018] [Accepted: 02/03/2018] [Indexed: 12/11/2022]
Abstract
Anomodontia was the most successful herbivorous clade of the mammalian stem lineage (non-mammalian synapsids) during the late Permian and Early Triassic. Among anomodonts, Dicynodontia stands apart because of the presence of an osseous beak that shows evidence of the insertion of a cornified sheath, the ramphotheca. In this study, fourteen anomodont specimens were microCT-scanned and their trigeminal canals reconstructed digitally to understand the origin and evolution of trigeminal nerve innervation of the ramphotheca. We show that the pattern of innervation of the anomodont "beak" is more similar to that in chelonians (the nasopalatine branch is enlarged and innervates the premaxillary part of the ramphotheca) than in birds (where the nasopalatine and maxillary branches play minor roles). The nasopalatine branch is noticeably enlarged in the beak-less basal anomodont Patranomodon, suggesting that this could be an anomodont or chainosaur synapomorphy. Our analyses suggest that the presence or absence of tusks and postcanine teeth are often accompanied by corresponding variations of the rami innervating the caniniform process and the alveolar region, respectively. The degree of ossification of the canal for the nasal ramus of the ophthalmic branch also appears to correlate with the presence of a nasal boss. The nasopalatine canal is absent from the premaxilla in the Bidentalia as they uniquely show a large plexus formed by the internal nasal branch of the maxillary canal instead. The elongated shape of this plexus in Lystrosaurus supports the hypothesis that the rostrum evolved as an elongation of the subnarial region of the snout. Finally, the atrophied and variable aspect of the trigeminal canals in Myosaurus supports the hypothesis that this genus had a reduced upper ramphotheca.
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Affiliation(s)
- Julien Benoit
- Evolutionary Studies Institute (ESI), School of Geosciences, University of the Witwatersrand, Johannesburg, 2050, South Africa
| | - Kenneth D Angielczyk
- Evolutionary Studies Institute (ESI), School of Geosciences, University of the Witwatersrand, Johannesburg, 2050, South Africa.,Integrative Research Center, Field Museum of Natural History, 1400 South Lake Shore Drive, Chicago, Illinois, 60605
| | - Juri A Miyamae
- Department of Geology & Geophysics, P.O. Box 208109, Yale University, New Haven, Connecticut, 06520-8109
| | - Paul Manger
- School of Anatomical Sciences, University of the Witwatersrand, Johannesburg, 2193, South Africa
| | - Vincent Fernandez
- European Synchrotron Radiation Facility, Beamline ID19, Grenoble, 38000, France
| | - Bruce Rubidge
- Evolutionary Studies Institute (ESI), School of Geosciences, University of the Witwatersrand, Johannesburg, 2050, South Africa
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Isaksson H, Le Cann S, Perdikouri C, Turunen MJ, Kaestner A, Tägil M, Hall SA, Tudisco E. Neutron tomographic imaging of bone-implant interface: Comparison with X-ray tomography. Bone 2017; 103:295-301. [PMID: 28739417 DOI: 10.1016/j.bone.2017.07.022] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Revised: 07/19/2017] [Accepted: 07/20/2017] [Indexed: 01/14/2023]
Abstract
Metal implants, in e.g. joint replacements, are generally considered to be a success. As mechanical stability is important for the longevity of a prosthesis, the biological reaction of the bone to the mechanical loading conditions after implantation and during remodelling determines its fate. The bone reaction at the implant interface can be studied using high-resolution imaging. However, commonly used X-ray imaging suffers from image artefacts in the close proximity of metal implants, which limit the possibility to closely examine the bone at the bone-implant interface. An alternative ex vivo 3D imaging method is offered by neutron tomography. Neutrons interact with matter differently than X-rays; therefore, this study explores if neutron tomography may be used to enrich studies on bone-implant interfaces. A stainless steel screw was implanted in a rat tibia and left to integrate for 6weeks. After extracting the tibia, the bone-screw construct was imaged using X-ray and neutron tomography at different resolutions. Artefacts were visible in all X-ray images in the close proximity of the implant, which limited the ability to accurately quantify the bone around the implant. In contrast, neutron images were free of metal artefacts, enabling full analysis of the bone-implant interface. Trabecular structural bone parameters were quantified in the metaphyseal bone away from the implant using all imaging modalities. The structural bone parameters were similar for all images except for the lowest resolution neutron images. This study presents the first proof-of-concept that neutron tomographic imaging can be used for ex-vivo evaluation of bone microstructure and that it constitutes a viable, new tool to study the bone-implant interface tissue remodelling.
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Affiliation(s)
- Hanna Isaksson
- Department of Biomedical Engineering, Lund University, Sweden; Department of Orthopaedics, Lund University, Sweden.
| | - Sophie Le Cann
- Department of Biomedical Engineering, Lund University, Sweden.
| | | | - Mikael J Turunen
- Department of Biomedical Engineering, Lund University, Sweden; Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
| | - Anders Kaestner
- Swiss Spallation Source, Paul Scherrer Institut, Switzerland.
| | - Magnus Tägil
- Department of Orthopaedics, Lund University, Sweden.
| | | | - Erika Tudisco
- Division of Geotechnical Engineering, Lund University, Sweden.
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Le Cann S, Tudisco E, Perdikouri C, Belfrage O, Kaestner A, Hall S, Tägil M, Isaksson H. Characterization of the bone-metal implant interface by Digital Volume Correlation of in-situ loading using neutron tomography. J Mech Behav Biomed Mater 2017; 75:271-278. [PMID: 28759839 DOI: 10.1016/j.jmbbm.2017.07.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 06/19/2017] [Accepted: 07/01/2017] [Indexed: 12/22/2022]
Abstract
Metallic implants are commonly used as surgical treatments for many orthopedic conditions. The long-term stability of implants relies on an adequate integration with the surrounding bone. Unsuccessful integration could lead to implant loosening. By combining mechanical loading with high-resolution 3D imaging methods, followed by image analysis such as Digital Volume Correlation (DVC), we aim at evaluating ex vivo the mechanical resistance of newly formed bone at the interface. X-rays tomography is commonly used to image bone but induces artefacts close to metallic components. Utilizing a different interaction with matter, neutron tomography is a promising alternative but has not yet been used in studies of bone mechanics. This work demonstrates that neutron tomography during in situ loading is a feasible tool to characterize the mechanical response of bone-implant interfaces, especially when combined with DVC. Experiments were performed where metal screws were implanted in rat tibiae during 4 weeks. The screws were pulled-out while the samples were sequentially imaged in situ with neutron tomography. The images were analyzed to quantify bone ingrowth around the implants. DVC was used to track the internal displacements and calculate the strain fields in the bone during loading. The neutron images were free of metal-related artefacts, which enabled accurate quantification of bone ingrowth on the screw (ranging from 60% to 71%). DVC allowed successful identification of the deformation and cracks that occurred during mechanical loading and led to final failure of the bone-implant interface.
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Affiliation(s)
- Sophie Le Cann
- Department of Biomedical Engineering, Lund University, 22100 Lund, Sweden.
| | - Erika Tudisco
- Division of Geotechnical Engineering, Lund University, Sweden.
| | | | - Ola Belfrage
- Department of Orthopaedics, Lund University, Sweden.
| | - Anders Kaestner
- Swiss Spallation Source, Paul Sheerer Institute, Switzerland.
| | - Stephen Hall
- Division of Solid Mechanics, Lund University, Sweden.
| | - Magnus Tägil
- Department of Orthopaedics, Lund University, Sweden.
| | - Hanna Isaksson
- Department of Biomedical Engineering, Lund University, 22100 Lund, Sweden; Department of Orthopaedics, Lund University, Sweden.
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Laaß M, Schillinger B, Kaestner A. What did the "Unossified zone" of the non-mammalian therapsid braincase house? J Morphol 2017. [PMID: 28621458 DOI: 10.1002/jmor.20583] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Most nonmammalian synapsids possess a mid-dorsal depression in the brain cavity known as the "unossified zone." It remains obscure which structures this zone contained, and, as candidates, the vermis of the cerebellum, the superior sagittal sinus, a junction of several blood vessels, the pineal gland or other midbrain structures were considered. Neutron tomography of a skull of Diictodon feliceps (Therapsida, Anomodontia) revealed some clear impressions of canals in this region of the brain cavity. Furthermore, the prootic sinus probably ran on the internal surface of the pila antotica and had a similar course in anomodonts as it has been proposed for cynodonts and Mesozoic mammals. Comparisons with the vascular systems of nonmammalian synapsids and mammals suggest that the unossified zone is best interpreted as a terminal chamber of the anterior segment of the medial head vein, which housed the junction of the superior sagittal sinus and the transverse sinuses. Consequently, the system of cranial vessels in Diictodon reveals a partial division of the medial head vein system into an anterior and a posterior segment at an early stage of synapsid evolution, which is consistent with the well-known common pattern of early ontogenetic development in amniotes. J. Morphol., 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Michael Laaß
- Faculty of Biology, Department of General Zoology, University of Duisburg-Essen, Universitätsstr. 5, Essen, D-45117, Germany
| | - Burkhard Schillinger
- Heinz Maier-Leibnitz Centre and Faculty for Physics E21, Technische Universität München, Lichtenbergstraße 1, Garching, D-85747, Germany
| | - Anders Kaestner
- Neutron Imaging and Activation Group, Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, Villigen, PSI, CH-5232, Switzerland
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Laaß M, Kaestner A. Evidence for convergent evolution of a neocortex-like structure in a late Permian therapsid. J Morphol 2017. [PMID: 28621462 DOI: 10.1002/jmor.20712] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The special sensory, motor, and cognitive capabilities of mammals mainly depend upon the neocortex, which is the six-layered cover of the mammalian forebrain. The origin of the neocortex is still controversial and the current view is that larger brains with neocortex first evolved in late Triassic Mammaliaformes. Here, we report the earliest evidence of a structure analogous to the mammalian neocortex in a forerunner of mammals, the fossorial anomodont Kawingasaurus fossilis from the late Permian of Tanzania. The endocranial cavity of Kawingasaurus is almost completely ossified, which allowed a less hypothetical virtual reconstruction of the brain endocast to be generated. A parietal foramen is absent. A small pit between the cerebral hemispheres is interpreted as a pineal body. The inflated cerebral hemispheres are demarcated from each other by a median sulcus and by a possible rhinal fissure from the rest of the endocast. The encephalization quotient estimated by using the method of Eisenberg is 0.52, which is 2-3 times larger than in other nonmammalian synapsids. Another remarkable feature are the extremely ramified infraorbital canals in the snout. The shape of the brain endocast, the extremely ramified maxillary canals as well as the small frontally placed eyes suggest that special sensory adaptations to the subterranean habitat such as a well developed sense of touch and binocular vision may have driven the parallel evolution of an equivalent of the mammalian neocortex and a mammal-like lemnothalamic visual system in Kawingasaurus. The gross anatomy of the brain endocast of Kawingasaurus supports the Outgroup Hypothesis, according to which the neocortex evolved from the dorsal pallium of an amphibian-like ancestor, which receives sensory projections from the lemnothalamic pathway. The enlarged brain as well as the absence of a parietal foramen may be an indication for a higher metabolic rate of Kawingasaurus compared to other nonmammalian synapsids.
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Affiliation(s)
- Michael Laaß
- Department of General Zoology, Faculty of Biology, University of Duisburg-Essen, Universitätsstr. 2, Essen, D-45117, Germany
| | - Anders Kaestner
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, Villigen PSI, CH-5232, Switzerland
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Abstract
AbstractVirtual paleontology is the study of fossils through three-dimensional digital visualizations; it represents a powerful and well-established set of tools for the analysis and dissemination of fossil data. Techniques are divisible into tomographic (i.e., slice-based) and surface-based types. Tomography has a long predigital history, but the recent explosion of virtual paleontology has resulted primarily from developments in X-ray computed tomography (CT), and of surface-based technologies (e.g., laser scanning). Destructive tomographic methods include forms of physical-optical tomography (e.g., serial grinding); these are powerful but problematic techniques. Focused Ion Beam (FIB) tomography is a modern alternative for microfossils; it is also destructive but is capable of extremely high resolutions. Nondestructive tomographic methods include the many forms of CT, which are the most widely used data-capture techniques at present, but are not universally applicable. Where CT is inappropriate, other nondestructive technologies (e.g., neutron tomography, magnetic resonance imaging, optical tomography) can prove suitable. Surface-based methods provide portable and convenient data capture for surface topography and texture, and might be appropriate when internal morphology is not of interest; technologies include laser scanning, photogrammetry, and mechanical digitization. Reconstruction methods that produce visualizations from raw data are many and various; selection of an appropriate workflow will depend on many factors, but is an important consideration that should be addressed prior to any study. The vast majority of three-dimensional fossils can now be studied using some form of virtual paleontology, and barriers to broader adaptation are being eroded. Technical issues regarding data sharing remain problematic. Technological developments continue; those promising tomographic recovery of compositional data are of particular relevance to paleontology.
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