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Kerber L, Roese-Miron L, Bubadué JM, Martinelli AG. Endocranial anatomy of the early prozostrodonts (Eucynodontia: Probainognathia) and the neurosensory evolution in mammal forerunners. Anat Rec (Hoboken) 2024; 307:1442-1473. [PMID: 37017195 DOI: 10.1002/ar.25215] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 03/09/2023] [Accepted: 03/09/2023] [Indexed: 04/06/2023]
Abstract
Prozostrodon brasiliensis and Therioherpeton cargnini are non-mammaliaform cynodonts that lived ~233 million years ago (late Carnian, Late Triassic) in western Gondwana. They represent some of the earliest divergent members of the clade Prozostrodontia, which includes "tritheledontids", tritylodontids, "brasilodontids", and mammaliaforms (including Mammalia as crown group). Here, we studied the endocranial anatomy (cranial endocast, nerves, vessels, ducts, ear region, and nasal cavity) of these two species. Our findings suggest that during the Carnian, early prozostrodonts had a brain with well-developed olfactory bulbs, expanded cerebral hemispheres divided by the interhemispheric sulcus, and absence of an unossified zone and pineal body. The morphology of the maxillary canal represents the necessary condition for the presence of facial vibrissae. A slight decrease in encephalization is observed at the origin of the clade Prozostrodontia. This new anatomical information provides evidence for the evolution of endocranial traits of the first prozotrodonts, a Late Triassic lineage that culminated in the origin of mammals.
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Affiliation(s)
- Leonardo Kerber
- Programa de Pós-Graduação em Biodiversidade Animal, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil
- Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia, Universidade Federal de Santa Maria (CAPPA/UFSM), São João do Polêsine, RS, Brazil
| | - Lívia Roese-Miron
- Programa de Pós-Graduação em Biodiversidade Animal, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil
- Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia, Universidade Federal de Santa Maria (CAPPA/UFSM), São João do Polêsine, RS, Brazil
| | - Jamile M Bubadué
- Laboratorio de Ciências Ambientais, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brazil
| | - Agustín G Martinelli
- Sección Paleontologia de Vertebrados, Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", Buenos Aires, Argentina
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2
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Maugoust J, Orliac MJ. Anatomical correlates and nomenclature of the chiropteran endocranial cast. Anat Rec (Hoboken) 2023; 306:2791-2829. [PMID: 37018745 DOI: 10.1002/ar.25206] [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: 11/14/2022] [Revised: 02/07/2023] [Accepted: 02/08/2023] [Indexed: 04/07/2023]
Abstract
Bats form a diverse group of mammals that are highly specialized in active flight and ultrasound echolocation. These specializations rely on adaptations that reflect on their morphoanatomy and have been tentatively linked to brain morphology and volumetry. Despite their small size and fragility, bat crania and natural braincase casts ("endocasts") have been preserved in the fossil record, which allows for investigating brain evolution and inferring paleobiology. Advances in imaging techniques have allowed virtual extraction of internal structures, assuming that the shape of the endocast reflects soft organ morphology. However, there is no direct correspondence between the endocast and internal structures because meninges and vascular tissues mark the inner braincase together with the brain they surround, resulting in a mosaic morphology of the endocast. The hypothesis suggesting that the endocast reflects the brain in terms of both external shape and volume has drastic implications when addressing brain evolution, but it has been rarely discussed. To date, only a single study addressed the correspondence between the brain and braincase in bats. Taking advantage of the advent of imaging techniques, we reviewed the anatomical, neuroanatomical, and angiological literature and compare this knowledge available on bat's braincase anatomy with anatomical observations using a sample of endocranial casts representing most modern bat families. Such comparison allows to propose a Chiroptera-scale nomenclature for future descriptions and comparisons among bat endocasts. Describing the imprints of the tissues surrounding the brain also allows to address to what extent brain features can be blurred or hidden (e.g., hypophysis, epiphysis, colliculi, flocculus). Furthermore, this approach encourages further study to formally test the proposed hypotheses.
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Affiliation(s)
- Jacob Maugoust
- Institut des Sciences de l'Evolution de Montpellier, département CHANGE, équipe Paléontologie, UMR 5554 Université de Montpellier, CNRS, IRD, EPHE, Place Eugène Bataillon, Montpellier Cedex 5, 34095, France
| | - Maeva Judith Orliac
- Institut des Sciences de l'Evolution de Montpellier, département CHANGE, équipe Paléontologie, UMR 5554 Université de Montpellier, CNRS, IRD, EPHE, Place Eugène Bataillon, Montpellier Cedex 5, 34095, France
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3
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Norton LA, Abdala F, Benoit J. Craniodental anatomy in Permian-Jurassic Cynodontia and Mammaliaformes (Synapsida, Therapsida) as a gateway to defining mammalian soft tissue and behavioural traits. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220084. [PMID: 37183903 PMCID: PMC10184251 DOI: 10.1098/rstb.2022.0084] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023] Open
Abstract
Mammals are diagnosed by more than 30 osteological characters (e.g. squamosal-dentary jaw joint, three inner ear ossicles, etc.) that are readily preserved in the fossil record. However, it is the suite of physiological, soft tissue and behavioural characters (e.g. endothermy, hair, lactation, isocortex and parental care), the evolutionary origins of which have eluded scholars for decades, that most prominently distinguishes living mammals from other amniotes. Here, we review recent works that illustrate how evolutionary changes concentrated in the cranial and dental morphology of mammalian ancestors, the Permian-Jurassic Cynodontia and Mammaliaformes, can potentially be used to document the origin of some of the most crucial defining features of mammals. We discuss how these soft tissue and behavioural traits are highly integrated, and how their evolution is intermingled with that of craniodental traits, thus enabling the tracing of their previously out-of-reach phylogenetic history. Most of these osteological and dental proxies, such as the maxillary canal, bony labyrinth and dental replacement only recently became more easily accessible-thanks, in large part, to the widespread use of X-ray microtomography scanning in palaeontology-because they are linked to internal cranial characters. This article is part of the theme issue 'The mammalian skull: development, structure and function'.
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Affiliation(s)
- Luke A Norton
- Evolutionary Studies Institute, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa
| | - Fernando Abdala
- Evolutionary Studies Institute, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa
- Unidad Ejecutora Lillo, CONICET-Fundación Miguel Lillo, Miguel Lillo 251, Tucumán 4000, Argentina
| | - Julien Benoit
- Evolutionary Studies Institute, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa
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4
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Melchor R, Perez M, Villegas P, Espinoza N, Umazano A, Cardonatto MC. Early Cretaceous lepidosaur (sphenodontian?) burrows. Sci Rep 2023; 13:10209. [PMID: 37353642 PMCID: PMC10290101 DOI: 10.1038/s41598-023-37385-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Accepted: 06/21/2023] [Indexed: 06/25/2023] Open
Abstract
Scarce fossil tetrapod burrows have been recorded in Cretaceous rocks, which is probably linked to the dominant equable climates that existed for most of this period. The occurrence of Cretaceous tetrapod burrows from Patagonia (Chubut Province, Argentina) dated between 118 and 115 million years ago, gives insights into their paleoecology and paleoenvironment. The rocks containing the tetrapod burrows are of pyroclastic origin and represent eolian dunes and ash-fall deposits, some reworked by fluvial currents and others showing soil development. Fossil burrow casts preserved in a paleosol are composed by a ramp with a slightly curved or straight path in plan-view and lacking bifurcation, a rounded termination with no enlargement, showing a reniform cross-section, and are assigned to the ichnospecies Reniformichnus katikatii. The strongly flattened cross-sectional shape of the burrow casts and comparison with modern lizard burrows suggest that the producers were lepidosaurs (body mass = 50-323 g). Among Cretaceous fossorial lepidosaurs from Patagonia, the best candidate is an eilenodontine sphenodontian. Sphenodontians burrowed in the fossil soils where also arthropods, earthworms and shrubby plants thrived. The rare occurrence of tetrapod burrows in Cretaceous rocks is linked to stressing conditions related to frequent arrival of volcanic ash and a semiarid seasonal climate.
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Affiliation(s)
- Ricardo Melchor
- Instituto de Ciencias de la Tierra y Ambientales de La Pampa (Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de La Pampa), Mendoza 109, 6300, Santa Rosa, La Pampa, Argentina.
- Departamento de Geología, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de La Pampa, Av. Uruguay 151, 6300, Santa Rosa, La Pampa, Argentina.
| | - Mariano Perez
- Departamento de Geología, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de La Pampa, Av. Uruguay 151, 6300, Santa Rosa, La Pampa, Argentina
| | - Pablo Villegas
- Instituto de Ciencias de la Tierra y Ambientales de La Pampa (Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de La Pampa), Mendoza 109, 6300, Santa Rosa, La Pampa, Argentina
| | - Nahuel Espinoza
- Instituto de Ciencias de la Tierra y Ambientales de La Pampa (Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de La Pampa), Mendoza 109, 6300, Santa Rosa, La Pampa, Argentina
| | - Aldo Umazano
- Instituto de Ciencias de la Tierra y Ambientales de La Pampa (Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de La Pampa), Mendoza 109, 6300, Santa Rosa, La Pampa, Argentina
- Departamento de Geología, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de La Pampa, Av. Uruguay 151, 6300, Santa Rosa, La Pampa, Argentina
| | - M Cristina Cardonatto
- Departamento de Geología, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de La Pampa, Av. Uruguay 151, 6300, Santa Rosa, La Pampa, Argentina
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5
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At the root of the mammalian mind: The sensory organs, brain and behavior of pre-mammalian synapsids. PROGRESS IN BRAIN RESEARCH 2023; 275:25-72. [PMID: 36841570 DOI: 10.1016/bs.pbr.2022.10.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
All modern mammals are descendants of the paraphyletic non-mammaliaform Synapsida, colloquially referred to as the "mammal-like reptiles." It has long been assumed that these mammalian ancestors were essentially reptile-like in their morphology, biology, and behavior, i.e., they had a small brain, displayed simple behavior, and their sensory organs were unrefined compared to those of modern mammals. Recent works have, however, revealed that neurological, sensory, and behavioral traits previously considered typically mammalian, such as whiskers, enhanced olfaction, nocturnality, parental care, and complex social interactions evolved before the origin of Mammaliaformes, among the early-diverging "mammal-like reptiles." In contrast, an enlarged brain did not evolve immediately after the origin of mammaliaforms. As such, in terms of paleoneurology, the last "mammal-like reptiles" were not significantly different from the earliest mammaliaforms. The abundant data and literature published in the last 10 years no longer supports the "three pulses" scenario of synapsid brain evolution proposed by Rowe and colleagues in 2011, but supports the new "outside-in" model of Rodrigues and colleagues proposed in 2018, instead. As Mesozoic reptiles were becoming the dominant taxa within terrestrial ecosystems, synapsids gradually adapted to smaller body sizes and nocturnality. This resulted in a sensory revolution in synapsids as olfaction, audition, and somatosensation compensated for the loss of visual cues. This altered sensory input is aligned with changes in the brain, the most significant of which was an increase in relative brain size.
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6
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Lang MM, Bertrand OC, San Martin Flores G, Law CJ, Abdul‐Sater J, Spakowski S, Silcox MT. Scaling Patterns of Cerebellar Petrosal Lobules in Euarchontoglires: Impacts of Ecology and Phylogeny. Anat Rec (Hoboken) 2022; 305:3472-3503. [DOI: 10.1002/ar.24929] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 02/02/2022] [Accepted: 02/21/2022] [Indexed: 11/11/2022]
Affiliation(s)
- Madlen M. Lang
- Department of Anthropology University of Toronto Scarborough Toronto ON Canada
| | - Ornella C. Bertrand
- School of GeoSciences University of Edinburgh, Grant Institute Edinburgh Scotland UK
| | | | - Chris J. Law
- Richard Gilder Graduate School, Department of Mammalogy, and Division of Paleontology American Museum of Natural History, 200 Central Park West New York NY
- Department of Biology University of Washington Seattle WA
- The University of Texas at Austin Austin TX
| | - Jade Abdul‐Sater
- Department of Anthropology University of Toronto Scarborough Toronto ON Canada
| | - Shayda Spakowski
- Department of Anthropology University of Toronto Scarborough Toronto ON Canada
| | - Mary T. Silcox
- Department of Anthropology University of Toronto Scarborough Toronto ON Canada
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7
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Bertrand OC, Shelley SL, Williamson TE, Wible JR, Chester SGB, Flynn JJ, Holbrook LT, Lyson TR, Meng J, Miller IM, Püschel HP, Smith T, Spaulding M, Tseng ZJ, Brusatte SL. Brawn before brains in placental mammals after the end-Cretaceous extinction. Science 2022; 376:80-85. [PMID: 35357913 DOI: 10.1126/science.abl5584] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Mammals are the most encephalized vertebrates, with the largest brains relative to body size. Placental mammals have particularly enlarged brains, with expanded neocortices for sensory integration, the origins of which are unclear. We used computed tomography scans of newly discovered Paleocene fossils to show that contrary to the convention that mammal brains have steadily enlarged over time, early placentals initially decreased their relative brain sizes because body mass increased at a faster rate. Later in the Eocene, multiple crown lineages independently acquired highly encephalized brains through marked growth in sensory regions. We argue that the placental radiation initially emphasized increases in body size as extinction survivors filled vacant niches. Brains eventually became larger as ecosystems saturated and competition intensified.
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Affiliation(s)
- Ornella C Bertrand
- School of GeoSciences, University of Edinburgh, Grant Institute, Edinburgh, Scotland EH9 3FE, UK
| | - Sarah L Shelley
- School of GeoSciences, University of Edinburgh, Grant Institute, Edinburgh, Scotland EH9 3FE, UK.,Section of Mammals, Carnegie Museum of Natural History, Pittsburgh, PA, USA
| | | | - John R Wible
- Section of Mammals, Carnegie Museum of Natural History, Pittsburgh, PA, USA
| | - Stephen G B Chester
- Department of Anthropology, Brooklyn College, City University of New York, Brooklyn, NY, USA.,Department of Anthropology, The Graduate Center, City University of New York, New York, NY, USA.,New York Consortium in Evolutionary Primatology, New York, NY, USA
| | - John J Flynn
- Division of Paleontology, American Museum of Natural History, New York, NY, USA.,Department of Earth and Environmental Sciences, Columbia University, New York, NY, USA.,Ecology, Evolutionary Biology, and Behavior subprogram, PhD Program in Biology, The Graduate Center, City University of New York, New York, NY, USA.,PhD Program in Earth and Environmental Sciences, The Graduate Center, City University of New York, New York, NY, USA
| | - Luke T Holbrook
- Department of Biological Sciences, Rowan University, Glassboro, NJ, USA
| | | | - Jin Meng
- Division of Paleontology, American Museum of Natural History, New York, NY, USA
| | - Ian M Miller
- Denver Museum of Nature & Science, Denver, CO, USA.,National Geographic Society, Washington, DC, USA
| | - Hans P Püschel
- School of GeoSciences, University of Edinburgh, Grant Institute, Edinburgh, Scotland EH9 3FE, UK
| | - Thierry Smith
- Directorate Earth and History of Life, Royal Belgian Institute of Natural Sciences, Brussels, Belgium
| | - Michelle Spaulding
- Department of Biological Sciences, Purdue University Northwest, Westville, IN, USA
| | - Z Jack Tseng
- Department of Integrative Biology and Museum of Paleontology, University of California, Berkeley, CA, USA
| | - Stephen L Brusatte
- School of GeoSciences, University of Edinburgh, Grant Institute, Edinburgh, Scotland EH9 3FE, UK.,New Mexico Museum of Natural History and Science, Albuquerque, NM, USA
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8
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Gheerbrant E, Schmitt A, Billet G. Petrosal and bony labyrinth morphology of the stem paenungulate mammal (Paenungulatomorpha) Ocepeia daouiensis from the Paleocene of Morocco. J Anat 2022; 240:595-611. [PMID: 32735727 PMCID: PMC8930808 DOI: 10.1111/joa.13255] [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: 12/13/2019] [Revised: 05/25/2020] [Accepted: 05/25/2020] [Indexed: 11/29/2022] Open
Abstract
Based on high-resolution computed tomography, we describe in detail the petrosal and inner ear anatomy of one of the few known African stem paenungulates (Paenungulatomorpha), Ocepeia daouiensis from the Selandian of the Ouled Abdoun phosphate basin (Morocco). The petrosal of Ocepeia displays some remarkable, probably derived features (among eutherians) such as relatively small pars cochlearis, pars canalicularis labyrinth (including small semicircular canals), a large wing-like pars mastoidea, a large and inflated tegmen tympani, and the dorsoventral orientation of the large canal for the ramus superior. The presence of small semicircular canals in Ocepeia is an interesting shared trait with tenrecoidean afrotherians. Otherwise, and consistent with a general primitive skull morphology, the middle ear and labyrinth of Ocepeia daouiensis is characterised by many plesiomorphic traits close to the eutherian generalised plan. This adds to the rather generalised morphology of the earliest crown paenungulates such as Eritherium, Phosphatherium and Seggeurius to support an ancestral paenungulatomorph morphotype poorly derived from the eutherian pattern. As a result, Ocepeia provides key morphological and fossil data to test phylogenetic relationships of the Afrotheria (including Paenungulatomorpha) at the placental root mostly inferred from molecular studies.
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Affiliation(s)
- Emmanuel Gheerbrant
- CR2PCentre de Recherche en Paléontologie ParisUMR 7207 (CNRS, MNHN, UPMC, Sorbonne Universités)ParisFrance
| | - Arnaud Schmitt
- CR2PCentre de Recherche en Paléontologie ParisUMR 7207 (CNRS, MNHN, UPMC, Sorbonne Universités)ParisFrance
| | - Guillaume Billet
- CR2PCentre de Recherche en Paléontologie ParisUMR 7207 (CNRS, MNHN, UPMC, Sorbonne Universités)ParisFrance
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9
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Perini FA, Macrini TE, Flynn JJ, Bamba K, Ni X, Croft DA, Wyss AR. Comparative Endocranial Anatomy, Encephalization, and Phylogeny of Notoungulata (Placentalia, Mammalia). J MAMM EVOL 2021. [DOI: 10.1007/s10914-021-09583-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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10
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Weisbecker V, Rowe T, Wroe S, Macrini TE, Garland KLS, Travouillon KJ, Black K, Archer M, Hand SJ, Berlin JC, Beck RMD, Ladevèze S, Sharp AC, Mardon K, Sherratt E. Global elongation and high shape flexibility as an evolutionary hypothesis of accommodating mammalian brains into skulls. Evolution 2021; 75:625-640. [PMID: 33483947 DOI: 10.1111/evo.14163] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Revised: 12/07/2020] [Accepted: 12/13/2020] [Indexed: 12/26/2022]
Abstract
Little is known about how the large brains of mammals are accommodated into the dazzling diversity of their skulls. It has been suggested that brain shape is influenced by relative brain size, that it evolves or develops according to extrinsic or intrinsic mechanical constraints, and that its shape can provide insights into its proportions and function. Here, we characterize the shape variation among 84 marsupial cranial endocasts of 57 species including fossils, using three-dimensional geometric morphometrics and virtual dissections. Statistical shape analysis revealed four main patterns: over half of endocast shape variation ranges from elongate and straight to globular and inclined; little allometric variation with respect to centroid size, and none for relative volume; no association between locomotion and endocast shape; limited association between endocast shape and previously published histological cortex volumes. Fossil species tend to have smaller cerebral hemispheres. We find divergent endocast shapes in closely related species and within species, and diverse morphologies superimposed over the main variation. An evolutionarily and individually malleable brain with a fundamental tendency to arrange into a spectrum of elongate-to-globular shapes-possibly mostly independent of brain function-may explain the accommodation of brains within the enormous diversity of mammalian skull form.
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Affiliation(s)
- Vera Weisbecker
- College of Science and Engineering, Flinders University, Bedford Park, SA, 5042, Australia.,School of Biological Sciences, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Timothy Rowe
- Department of Geological Sciences, The University of Texas at Austin, Austin, Texas, 78712
| | - Stephen Wroe
- School of Environmental and Rural Science, University of New England, Armidale, NSW, 2351, Australia
| | - Thomas E Macrini
- Department of Biological Sciences, St. Mary's University, San Antonio, Texas, 78228
| | | | - Kenny J Travouillon
- Collections and Research, Western Australian Museum, Welshpool, WA, 6986, Australia
| | - Karen Black
- Earth and Sustainability Science Research Center, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Michael Archer
- Earth and Sustainability Science Research Center, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Suzanne J Hand
- Earth and Sustainability Science Research Center, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Jeri C Berlin
- Department of Geological Sciences, The University of Texas at Austin, Austin, Texas, 78712
| | - Robin M D Beck
- School of Science, Engineering and Environment, University of Salford, Salford, M5 4WT, United Kingdom
| | - Sandrine Ladevèze
- CR2P UMR 7207, CNRS/MNHN/Sorbonne Université, Muséum National d'Histoire Naturelle, Paris, F-75005, France
| | - Alana C Sharp
- Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, L7 8TX, United Kingdom
| | - Karine Mardon
- Centre of Advanced Imaging, The University of Queensland, St. Lucia, QLD, 4072, Australia
| | - Emma Sherratt
- School of Biological Sciences, The University of Adelaide, Adelaide, SA, 5005, Australia
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11
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Numerical Analysis of the Cerebral Cortex in Diprotodontids (Marsupialia; Australidelphia) and Comparison with Eutherian Brains. ZOOLOGY 2020; 143:125845. [DOI: 10.1016/j.zool.2020.125845] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 09/09/2020] [Accepted: 09/11/2020] [Indexed: 11/22/2022]
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12
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Eppenberger PE, Čavka M, Radović S, Paar D, Buzjak N, Ahern JCM, Biedermann P, Gruber P, Novak M, Janković I. Radiographic analysis and virtual cleaning of a bioarchaeological remain enclosed in mineral deposits from a limestone cave. Eur Radiol Exp 2020; 4:41. [PMID: 32642831 PMCID: PMC7343914 DOI: 10.1186/s41747-020-00166-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Accepted: 06/03/2020] [Indexed: 11/10/2022] Open
Abstract
In limestone caves, environmental processes often cause alterations of human or animal skeletal remains, complicating classical analytical methods. Exemplary, a proximal femoral skeletal fragment, enclosed by a thick layer of speleothemic calcite deposits, was discovered during the exploration of the Bedara cave in Žumberak, Croatia. An examination without removal of the surrounding mineral deposits, possibly leading to damage of the specimen, was, therefore, desirable.We describe and discuss the applied techniques, including clinical computed tomography, virtual cleaning by a specially developed segmentation protocol using an open-source DICOM viewer, and virtual visualisation and dimensioning using computer-aided design software, so that this "hidden" specimen could be non-invasively examined in great detail. We also report on the circumstances and origin of the find, the results of radiocarbon dating, and its anatomical and taxonomic identification, according to which, the bone fragment belonged to a wild boar (Sus scrofa) from the timeframe of the Middle Eneolithic Retz-Gajary culture in the region (4,781 ± 35 years before present). This study provides a reference for future paleontological and anthropological analyses, seeking to unlock the enormous potential of anatomical studies of comparable skeletal remains that are either petrified or enclosed in speleothemic deposits.
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Affiliation(s)
- Patrick E Eppenberger
- Institute of Evolutionary Medicine, University of Zurich, Winterthurerstr, 190, CH-8057, Zurich, Switzerland.
| | - Mislav Čavka
- Department of Diagnostic and Interventional Radiology, University Hospital Centre "Zagreb", Zagreb, Croatia.,School of Medicine, Chair of Social Medicine and Organization of Healthcare, University Zagreb, Zagreb, Croatia
| | - Siniša Radović
- Institute for Quaternary Paleontology and Geology, Croatian Academy of Sciences and Arts, Zagreb, Croatia
| | - Dalibor Paar
- Department of Physics, Faculty of Science, University Zagreb, Zagreb, Croatia
| | - Nenad Buzjak
- Department of Geography, Faculty of Science, University Zagreb, Zagreb, Croatia
| | - James C M Ahern
- Department of Anthropology, University of Wyoming, Laramie, WY, USA
| | - Philipp Biedermann
- Institute of Evolutionary Medicine, University of Zurich, Winterthurerstr, 190, CH-8057, Zurich, Switzerland
| | - Philipp Gruber
- Institute of Evolutionary Medicine, University of Zurich, Winterthurerstr, 190, CH-8057, Zurich, Switzerland.,Department of Neuroradiology, Kantonsspital Aarau, Aarau, Switzerland
| | - Mario Novak
- Institute for Anthropological Research, Centre for Applied Bioanthropology, Zagreb, Croatia
| | - Ivor Janković
- Department of Anthropology, University of Wyoming, Laramie, WY, USA.,Institute for Anthropological Research, Centre for Applied Bioanthropology, Zagreb, Croatia
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13
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Bertrand OC, Shelley SL, Wible JR, Williamson TE, Holbrook LT, Chester SGB, Butler IB, Brusatte SL. Virtual endocranial and inner ear endocasts of the Paleocene 'condylarth' Chriacus: new insight into the neurosensory system and evolution of early placental mammals. J Anat 2019; 236:21-49. [PMID: 31667836 DOI: 10.1111/joa.13084] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/08/2019] [Indexed: 02/06/2023] Open
Abstract
The end-Cretaceous mass extinction allowed placental mammals to diversify ecologically and taxonomically as they filled ecological niches once occupied by non-avian dinosaurs and more basal mammals. Little is known, however, about how the neurosensory systems of mammals changed after the extinction, and what role these systems played in mammalian diversification. We here use high-resolution computed tomography (CT) scanning to describe the endocranial and inner ear endocasts of two species, Chriacus pelvidens and Chriacus baldwini, which belong to a cluster of 'archaic' placental mammals called 'arctocyonid condylarths' that thrived during the ca. 10 million years after the extinction (the Paleocene Epoch), but whose relationships to extant placentals are poorly understood. The endocasts provide new insight into the paleobiology of the long-mysterious 'arctocyonids', and suggest that Chriacus was an animal with an encephalization quotient (EQ) range of 0.12-0.41, which probably relied more on its sense of smell than vision, because the olfactory bulbs are proportionally large but the neocortex and petrosal lobules are less developed. Agility scores, estimated from the dimensions of the semicircular canals of the inner ear, indicate that Chriacus was slow to moderately agile, and its hearing capabilities, estimated from cochlear dimensions, suggest similarities with the extant aardvark. Chriacus shares many brain features with other Paleocene mammals, such as a small lissencephalic brain, large olfactory bulbs and small petrosal lobules, which are likely plesiomorphic for Placentalia. The inner ear of Chriacus also shares derived characteristics of the elliptical and spherical recesses with extinct species that belong to Euungulata, the extant placental group that includes artiodactyls and perissodactyls. This lends key evidence to the hypothesized close relationship between Chriacus and the extant ungulate groups, and demonstrates that neurosensory features can provide important insight into both the paleobiology and relationships of early placental mammals.
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Affiliation(s)
- Ornella C Bertrand
- School of GeoSciences, University of Edinburgh, Grant Institute, Edinburgh, UK
| | - Sarah L Shelley
- Section of Mammals, Carnegie Museum of Natural History, Pittsburgh, PA, USA
| | - John R Wible
- Section of Mammals, Carnegie Museum of Natural History, Pittsburgh, PA, USA
| | | | - Luke T Holbrook
- Department of Biological Sciences, Rowan University, Glassboro, NJ, USA
| | - Stephen G B Chester
- Department of Anthropology and Archaeology, Brooklyn College, City University of New York, Brooklyn, NY, USA.,Department of Anthropology, The Graduate Center, City University of New York, New York, NY, USA.,New York Consortium in Evolutionary Primatology, New York, NY, USA
| | - Ian B Butler
- School of GeoSciences, University of Edinburgh, Grant Institute, Edinburgh, UK
| | - Stephen L Brusatte
- School of GeoSciences, University of Edinburgh, Grant Institute, Edinburgh, UK.,New Mexico Museum of Natural History and Science, Albuquerque, NM, USA
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14
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Lyras GA. Brain Changes during Phyletic Dwarfing in Elephants and Hippos. BRAIN, BEHAVIOR AND EVOLUTION 2019; 92:167-181. [PMID: 30943507 DOI: 10.1159/000497268] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Accepted: 01/27/2019] [Indexed: 11/19/2022]
Abstract
Of all known insular mammals, hippos and elephants present the extremes of body size decrease, reducing to 4 and a mere 2% of their ancestral mainland size, respectively. Despite the numerous studies on these taxa, what happens to their relative brain size during phyletic dwarfing is not well known, and results are sometimes conflicting. For example, relative brain size increase has been noted in the Sicilian dwarf elephant, Palaeoloxodon falconeri, whereas relative brain size decrease has been postulated for Malagasy dwarf hippos. Here, I perform an analysis of brain, skull, and body size of 3 insular elephants (Palaeoloxodon "mnaidriensis," P. tiliensis, and P. falconeri) and 3 insular hippos (Hippopotamus madagascariensis, H. lemerlei, and H. minor) to address this issue and to test whether relative brain size in phyletic dwarf species can be predicted. The results presented here show that the encephalization of all insular elephants and hippos is higher than that of their continental relatives. P. falconeri in particular has an enormous encephalization increase, which has so far not been reported in any other insular mammal. Insular brain size cannot be reliably predicted using either static allometric or ontogenetic scaling models. The results of this study indicate that insular dwarf species follow brain-body allometric relationships different from the expected patterns seen for their mainland relatives.
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Affiliation(s)
- George A Lyras
- Department of Geology and Geoenvironment, National and Kapodistrian University of Athens, Athens, Greece,
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15
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Cameron J, Shelley SL, Williamson TE, Brusatte SL. The Brain and Inner Ear of the Early Paleocene “Condylarth”
Carsioptychus coarctatus
: Implications for Early Placental Mammal Neurosensory Biology and Behavior. Anat Rec (Hoboken) 2018; 302:306-324. [DOI: 10.1002/ar.23903] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 04/04/2018] [Accepted: 04/16/2018] [Indexed: 11/08/2022]
Affiliation(s)
- Joe Cameron
- School of GeoSciences University of Edinburgh, Grant Institute Edinburgh Scotland UK
| | - Sarah L. Shelley
- School of GeoSciences University of Edinburgh, Grant Institute Edinburgh Scotland UK
| | | | - Stephen L. Brusatte
- School of GeoSciences University of Edinburgh, Grant Institute Edinburgh Scotland UK
- New Mexico Museum of Natural History and Science Albuquerque New Mexico
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16
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Racicot RA, Darroch SAF, Kohno N. Neuroanatomy and inner ear labyrinths of the narwhal, Monodon monoceros, and beluga, Delphinapterus leucas (Cetacea: Monodontidae). J Anat 2018; 233:421-439. [PMID: 30033539 PMCID: PMC6131972 DOI: 10.1111/joa.12862] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/20/2018] [Indexed: 10/28/2022] Open
Abstract
Narwhals (Monodon monoceros) and belugas (Delphinapterus leucas) are the only extant members of the Monodontidae, and are charismatic Arctic-endemic cetaceans that are at risk from global change. Investigating the anatomy and sensory apparatuses of these animals is essential to understanding their ecology and evolution, and informs efforts for their conservation. Here, we use X-ray CT scans to compare aspects of the endocranial and inner ear labyrinth anatomy of extant monodontids and use the overall morphology to draw larger inferences about the relationship between morphology and ecology. We show that differences in the shape of the brain, vasculature, and neural canals of both species may relate to differences in diving and other behaviors. The cochleae are similar in morphology in the two species, signifying similar hearing ranges and a close evolutionary relationship. Lastly, we compare two different methods for calculating 90var - a calculation independent of body size that is increasingly being used as a proxy for habitat preference. We show that a 'direct' angular measurement method shows significant differences between Arctic and other habitat preferences, but angle measurements based on planes through the semicircular canals do not, emphasizing the need for more detailed study and standardization of this measurement. This work represents the first comparative internal anatomical study of the endocranium and inner ear labyrinths of this small clade of toothed whales.
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Affiliation(s)
- Rachel A. Racicot
- Department of Earth and Environmental SciencesVanderbilt UniversityNashvilleTNUSA
- The Dinosaur InstituteNatural History Museum of Los Angeles CountyLos AngelesCAUSA
| | - Simon A. F. Darroch
- Department of Earth and Environmental SciencesVanderbilt UniversityNashvilleTNUSA
| | - Naoki Kohno
- Department of Geology and PaleontologyNational Museum of Nature and ScienceTokyoJapan
- Graduate School of Life and Environmental SciencesUniversity of TsukubaTsukubaJapan
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17
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Boscaini A, Iurino DA, Sardella R, Tirao G, Gaudin TJ, Pujos F. Digital Cranial Endocasts of the Extinct Sloth Glossotherium robustum (Xenarthra, Mylodontidae) from the Late Pleistocene of Argentina: Description and Comparison with the Extant Sloths. J MAMM EVOL 2018. [DOI: 10.1007/s10914-018-9441-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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18
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Huttenlocker AK, Grossnickle DM, Kirkland JI, Schultz JA, Luo ZX. Late-surviving stem mammal links the lowermost Cretaceous of North America and Gondwana. Nature 2018; 558:108-112. [DOI: 10.1038/s41586-018-0126-y] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 04/10/2018] [Indexed: 11/09/2022]
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19
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Dome-headed, small-brained island mammal from the Late Cretaceous of Romania. Proc Natl Acad Sci U S A 2018; 115:4857-4862. [PMID: 29686084 DOI: 10.1073/pnas.1801143115] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The island effect is a well-known evolutionary phenomenon, in which island-dwelling species isolated in a resource-limited environment often modify their size, anatomy, and behaviors compared with mainland relatives. This has been well documented in modern and Cenozoic mammals, but it remains unclear whether older, more primitive Mesozoic mammals responded in similar ways to island habitats. We describe a reasonably complete and well-preserved skeleton of a kogaionid, an enigmatic radiation of Cretaceous island-dwelling multituberculate mammals previously represented by fragmentary fossils. This skeleton, from the latest Cretaceous of Romania, belongs to a previously unreported genus and species that possesses several aberrant features, including an autapomorphically domed skull and one of the smallest brains relative to body size of any advanced mammaliaform, which nonetheless retains enlarged olfactory bulbs and paraflocculi for sensory processing. Drawing on parallels with more recent island mammals, we interpret these unusual neurosensory features as related to the island effect. This indicates that the ability to adapt to insular environments developed early in mammalian history, before the advent of therian mammals, and mammals with insular-related modifications were key components of well-known dwarfed dinosaur faunas. Furthermore, the specimen suggests that brain size reduction, in association with heightened sensory acuity but without marked body size change, is a novel expression of the island effect in mammals.
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20
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New Virtual Endocasts of Eocene Ischyromyidae and Their Relevance in Evaluating Neurological Changes Occurring Through Time in Rodentia. J MAMM EVOL 2018. [DOI: 10.1007/s10914-017-9425-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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21
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Virtual Endocast Morphology of Mesotheriidae (Mammalia, Notoungulata, Typotheria): New Insights and Implications on Notoungulate Encephalization and Brain Evolution. J MAMM EVOL 2017. [DOI: 10.1007/s10914-017-9416-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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22
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Benoit J, Manger PR, Norton L, Fernandez V, Rubidge BS. Synchrotron scanning reveals the palaeoneurology of the head-butting Moschops capensis (Therapsida, Dinocephalia). PeerJ 2017; 5:e3496. [PMID: 28828230 PMCID: PMC5554600 DOI: 10.7717/peerj.3496] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Accepted: 06/02/2017] [Indexed: 12/17/2022] Open
Abstract
Dinocephalian therapsids are renowned for their massive, pachyostotic and ornamented skulls adapted for head-to-head fighting during intraspecific combat. Synchrotron scanning of the tapinocephalid Moschops capensis reveals, for the first time, numerous anatomical adaptations of the central nervous system related to this combative behaviour. Many neural structures (such as the brain, inner ear and ophthalmic branch of the trigeminal nerve) were completely enclosed and protected by bones, which is unusual for non-mammaliaform therapsids. The nearly complete ossification of the braincase enables precise determination of the brain cavity volume and encephalization quotient, which appears greater than expected for such a large and early herbivore. The practice of head butting is often associated with complex social behaviours and gregariousness in extant species, which are known to influence brain size evolution. Additionally, the plane of the lateral (horizontal) semicircular canal of the bony labyrinth is oriented nearly vertically if the skull is held horizontally, which suggests that the natural position of the head was inclined about 60–65°to the horizontal. This is consistent with the fighting position inferred from osteology, as well as ground-level browsing. Finally, the unusually large parietal tube may have been filled with thick conjunctive tissue to protect the delicate pineal eye from injury sustained during head butting.
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Affiliation(s)
- Julien Benoit
- Evolutionary Institute, School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa.,School of Anatomical Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Paul R Manger
- School of Anatomical Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Luke Norton
- Evolutionary Institute, School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Vincent Fernandez
- Beamline ID19, European Synchrotron Radiation Facility, Grenoble, France
| | - Bruce S Rubidge
- Evolutionary Institute, School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
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23
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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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24
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Origin of the Lateral Wall of the Mammalian Skull: Fossils, Monotremes and Therians Revisited. J MAMM EVOL 2017. [DOI: 10.1007/s10914-017-9388-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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25
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Bertrand OC, Amador‐Mughal F, Silcox MT. Virtual endocast of the early Oligocene Cedromus wilsoni (Cedromurinae) and brain evolution in squirrels. J Anat 2017; 230:128-151. [PMID: 27580644 PMCID: PMC5192888 DOI: 10.1111/joa.12537] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/19/2016] [Indexed: 01/21/2023] Open
Abstract
Extant squirrels exhibit extensive variation in brain size and shape, but published endocranial data for living squirrels are limited, and no study has ever examined brain evolution in Sciuridae from the perspective of the fossil record to understand how this diversity emerged. We describe the first virtual endocast for a fossil sciurid, Cedromus wilsoni, which is known from a complete cranium from Wyoming (Orellan, Oligocene), and make comparisons to a diverse sample of virtual endocasts for living sciurids (N = 20). The virtual endocasts were obtained from high-resolution X-ray micro-computed tomography data. Comparisons were also made with endocasts of extinct ischyromyid rodents, the most primitive rodents known from an endocranial record, which provide the opportunity to study the neuroanatomical changes occurring near the base of Sciuridae. The encephalization quotient of C. wilsoni is higher than that of Ischyromys typus from the same epoch, and falls within the range of modern terrestrial squirrel variation, but below the range of extant scansorial, arboreal and gliding sciurids when using cheek-tooth area for the estimation of body mass. In a principal components analysis, the shape of the endocast of C. wilsoni is found to be intermediate between that of primitive fossil taxa and the modern sample. Cedromus wilsoni has a more expanded neocortical surface area, especially the caudal region of the cerebrum, compared with ischyromyid rodents. Furthermore, C. wilsoni had proportionally larger paraflocculi and a more complex cerebellar morphology compared with ischyromyid rodents. These neurological differences may be associated with improvements in vision, although it is worth noting that the size of the parts of the brain most directly involved with vision [the rostral (superior) colliculi and the primary visual cortex] cannot be directly assessed on endocasts. The changes observed could also relate to balance and limb coordination. Ultimately, the available evidence suggests that early squirrels were more agile and visually oriented animals compared with more primitive rodents, which may relate to the process of becoming arboreal. Extant sciurids have an even more expanded neocortical surface area, while exhibiting proportionally smaller paraflocculi, compared with C. wilsoni. This suggests that the neocortex may continue increasing in size in more recent sciurid rodents in relation to other factors than arboreality. Despite the fact that both Primates and Rodentia exhibit neocortical expansion through time, since the adoption of arboreality preceded major increases in the neocortex in Primates, those neurological changes may be related to different ecological factors, underlining the complexity of the inter-relationship between time and ecology in shaping the brain in even closely related clades.
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Affiliation(s)
- Ornella C. Bertrand
- Department of AnthropologyUniversity of Toronto ScarboroughTorontoOntarioCanada
| | | | - Mary T. Silcox
- Department of AnthropologyUniversity of Toronto ScarboroughTorontoOntarioCanada
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26
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Balanoff AM, Bever GS, Colbert MW, Clarke JA, Field DJ, Gignac PM, Ksepka DT, Ridgely RC, Smith NA, Torres CR, Walsh S, Witmer LM. Best practices for digitally constructing endocranial casts: examples from birds and their dinosaurian relatives. J Anat 2016; 229:173-90. [PMID: 26403623 PMCID: PMC4948053 DOI: 10.1111/joa.12378] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/17/2015] [Indexed: 11/28/2022] Open
Abstract
The rapidly expanding interest in, and availability of, digital tomography data to visualize casts of the vertebrate endocranial cavity housing the brain (endocasts) presents new opportunities and challenges to the field of comparative neuroanatomy. The opportunities are many, ranging from the relatively rapid acquisition of data to the unprecedented ability to integrate critically important fossil taxa. The challenges consist of navigating the logistical barriers that often separate a researcher from high-quality data and minimizing the amount of non-biological variation expressed in endocasts - variation that may confound meaningful and synthetic results. Our purpose here is to outline preferred approaches for acquiring digital tomographic data, converting those data to an endocast, and making those endocasts as meaningful as possible when considered in a comparative context. This review is intended to benefit those just getting started in the field but also serves to initiate further discussion between active endocast researchers regarding the best practices for advancing the discipline. Congruent with the theme of this volume, we draw our examples from birds and the highly encephalized non-avian dinosaurs that comprise closely related outgroups along their phylogenetic stem lineage.
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Affiliation(s)
- Amy M. Balanoff
- Department of Anatomical SciencesStony Brook UniversityStony BrookNYUSA
| | - G. S. Bever
- Department of AnatomyNew York Institute of TechnologyCollege of Osteopathic MedicineOld WestburyNYUSA
| | - Matthew W. Colbert
- Department of Geological SciencesThe University of Texas at AustinAustinTXUSA
| | - Julia A. Clarke
- Department of Geological SciencesThe University of Texas at AustinAustinTXUSA
| | - Daniel J. Field
- Department of Geology and GeophysicsYale UniversityNew HavenCTUSA
| | - Paul M. Gignac
- Department of Anatomy and Cell BiologyOklahoma State University Center for Health SciencesTulsaOKUSA
| | | | - Ryan C. Ridgely
- Department of Biomedical SciencesHeritage College of Osteopathic MedicineOhio UniversityAthensOHUSA
| | - N. Adam Smith
- Department of Earth SciencesThe Field Museum of Natural HistoryChicagoILUSA
| | | | - Stig Walsh
- Department of Natural SciencesNational Museums ScotlandEdinburghUK
| | - Lawrence M. Witmer
- Department of Biomedical SciencesHeritage College of Osteopathic MedicineOhio UniversityAthensOHUSA
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Forasiepi AM, MacPhee RDE, Del Pino SH, Schmidt GI, Amson E, Grohé C. Exceptional Skull of Huayqueriana (Mammalia, Litopterna, Macraucheniidae) From the Late Miocene of Argentina: Anatomy, Systematics, and Paleobiological Implications. BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY 2016. [DOI: 10.1206/0003-0090-404.1.1] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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28
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Anterior commissure versus corpus callosum: A quantitative comparison across mammals. ZOOLOGY 2016; 119:126-136. [DOI: 10.1016/j.zool.2016.02.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 01/11/2016] [Accepted: 02/22/2016] [Indexed: 11/20/2022]
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29
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Mota B, Herculano-Houzel S. Response to Comments on "Cortical folding scales universally with surface area and thickness, not number of neurons". Science 2016; 351:826. [PMID: 26912888 DOI: 10.1126/science.aad2346] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
De Lussanet claims that our model that accounts for the degree of folding of the cerebral cortex based on the product of cortical surface area and the square root of cortical thickness is better reduced to the product of gray-matter proportion and folding index. Lewitus et al., in turn, claim that the assumptions of our model are in conflict with experimental data; that the model does not accurately fit the data; and that the ancestral mammalian brain was gyrencephalic. Here, we show that both claims are inappropriate.
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Affiliation(s)
- Bruno Mota
- Instituto de Física, Universidade Federal do Rio de Janeiro, Brasil
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30
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Bertrand OC, Amador-Mughal F, Silcox MT. Virtual endocasts of Eocene Paramys (Paramyinae): oldest endocranial record for Rodentia and early brain evolution in Euarchontoglires. Proc Biol Sci 2016; 283:20152316. [PMID: 26817776 PMCID: PMC4795019 DOI: 10.1098/rspb.2015.2316] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Accepted: 01/07/2016] [Indexed: 11/12/2022] Open
Abstract
Understanding the pattern of brain evolution in early rodents is central to reconstructing the ancestral condition for Glires, and for other members of Euarchontoglires including Primates. We describe the oldest virtual endocasts known for fossil rodents, which pertain to Paramys copei (Early Eocene) and Paramys delicatus (Middle Eocene). Both specimens of Paramys have larger olfactory bulbs and smaller paraflocculi relative to total endocranial volume than later occurring rodents, which may be primitive traits for Rodentia. The encephalization quotients (EQs) of Pa. copei and Pa. delicatus are higher than that of later occurring (Oligocene) Ischyromys typus, which contradicts the hypothesis that EQ increases through time in all mammalian orders. However, both species of Paramys have a lower relative neocortical surface area than later rodents, suggesting neocorticalization occurred through time in this Order, although to a lesser degree than in Primates. Paramys has a higher EQ but a lower neocortical ratio than any stem primate. This result contrasts with the idea that primates were always exceptional in their degree of overall encephalization and shows that relative brain size and neocortical surface area do not necessarily covary through time. As such, these data contradict assumptions made about the pattern of brain evolution in Euarchontoglires.
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Affiliation(s)
- Ornella C Bertrand
- Department of Anthropology, University of Toronto Scarborough, Toronto, Ontario, Canada M1C 1A4
| | - Farrah Amador-Mughal
- Department of Anthropology, University of Toronto Scarborough, Toronto, Ontario, Canada M1C 1A4
| | - Mary T Silcox
- Department of Anthropology, University of Toronto Scarborough, Toronto, Ontario, Canada M1C 1A4
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31
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Laaß M. Virtual reconstruction and description of the cranial endocast of Pristerodon mackayi (Therapsida, Anomodontia). J Morphol 2015; 276:1089-99. [PMID: 26129638 DOI: 10.1002/jmor.20397] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 03/02/2015] [Accepted: 04/25/2015] [Indexed: 11/06/2022]
Abstract
The cranial endocast of Pristerodon mackayi is described, which has been virtually reconstructed on the basis of neutron tomographic data. The gross anatomy of the cranial endocast of Pristerodon resembles other nonmammalian synapsids such as Thrinaxodon liorhinus in having a narrow, tubular forebrain, well developed olfactory bulbs, a large parietal foramen and unossified zone. As it is the case in cynodonts the hindbrain of Pristerodon is broader than the mid- and forebrain. Large paraflocculi are developed. The medulla oblongata can be well distinguished from the pons. The pons is divided by a median ridge into two portions. There is no evidence for a neocortex, which seems to be also reflected in the low encephalization quotient of 0.18 estimated according to the method of Eisenberg.
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Affiliation(s)
- Michael Laaß
- Department of General Zoology, Faculty of Biology, University of Duisburg-Essen, Duisburg-Essen, Germany
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First Digital Cranial Endocasts of late Oligocene Notohippidae (Notoungulata): Implications for Endemic South American Ungulates Brain Evolution. J MAMM EVOL 2015. [DOI: 10.1007/s10914-015-9298-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Intraspecific Variation of Endocranial Structures in Extant Equus: A Prelude to Endocranial Studies in Fossil Equoids. J MAMM EVOL 2015. [DOI: 10.1007/s10914-015-9293-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Billet G, de Muizon C, Schellhorn R, Ruf I, Ladevèze S, Bergqvist L. Petrosal and inner ear anatomy and allometry amongst specimens referred to Litopterna (Placentalia). Zool J Linn Soc 2015. [DOI: 10.1111/zoj.12219] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Guillaume Billet
- Steinmann-Institut für Geologie; Mineralogie und Paläontologie; Rheinische Friedrich-Wilhelms-Universität Bonn; Nussallee 8 53115 Bonn Germany
- CR2P - UMR 7207 CNRS; MNHN; Univ Paris 06 - Muséum national d'Histoire naturelle; 8 rue Buffon CP 38 75005 Paris France
| | - Christian de Muizon
- CR2P - UMR 7207 CNRS; MNHN; Univ Paris 06 - Muséum national d'Histoire naturelle; 8 rue Buffon CP 38 75005 Paris France
| | - Rico Schellhorn
- Steinmann-Institut für Geologie; Mineralogie und Paläontologie; Rheinische Friedrich-Wilhelms-Universität Bonn; Nussallee 8 53115 Bonn Germany
| | - Irina Ruf
- Steinmann-Institut für Geologie; Mineralogie und Paläontologie; Rheinische Friedrich-Wilhelms-Universität Bonn; Nussallee 8 53115 Bonn Germany
- Senckenberg Forschungsinstitut und Naturmuseum Frankfurt; Abteilung Paläoanthropologie und Messelforschung; Senckenberganlage 25 60325 Frankfurt am Main Germany
| | - Sandrine Ladevèze
- CR2P - UMR 7207 CNRS; MNHN; Univ Paris 06 - Muséum national d'Histoire naturelle; 8 rue Buffon CP 38 75005 Paris France
| | - Lilian Bergqvist
- Avenida Athos da Silveira Ramos; 274, bloco G; Centro de Ciências Matemáticas e da Natureza; Universidade Federal do Rio de Janeiro; Rio de Janeiro 21941-916 Brasil
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Kirk EC, Daghighi P, Macrini TE, Bhullar BAS, Rowe TB. Cranial anatomy of the Duchesnean primate Rooneyia viejaensis : New insights from high resolution computed tomography. J Hum Evol 2014; 74:82-95. [DOI: 10.1016/j.jhevol.2014.03.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Revised: 02/28/2014] [Accepted: 03/13/2014] [Indexed: 11/16/2022]
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Ahrens HE. Morphometric study of phylogenetic and ecologic signals in procyonid (mammalia: carnivora) endocasts. Anat Rec (Hoboken) 2014; 297:2318-30. [PMID: 25066912 DOI: 10.1002/ar.22996] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Accepted: 05/30/2014] [Indexed: 11/09/2022]
Abstract
Endocasts provide a proxy for brain morphology but are rarely incorporated in phylogenetic analyses despite the potential for new suites of characters. The phylogeny of Procyonidae, a carnivoran family with relatively limited taxonomic diversity, is not well resolved because morphological and molecular data yield conflicting topologies. The presence of phylogenetic and ecologic signals in the endocasts of procyonids will be determined using three-dimensional geometric morphometrics. Endocasts of seven ingroup species and four outgroup species were digitally rendered and 21 landmarks were collected from the endocast surface. Two phylogenetic hypotheses of Procyonidae will be examined using methods testing for phylogenetic signal in morphometric data. In analyses of all taxa, there is significant phylogenetic signal in brain shape for both the morphological and molecular topologies. However, the analyses of ingroup taxa recover a significant phylogenetic signal for the morphological topology only. These results indicate support for the molecular outgroup topology, but not the ingroup topology given the brain shape data. Further examination of brain shape using principal components analysis and wireframe comparisons suggests procyonids possess more developed areas of the brain associated with motor control, spatial perception, and balance relative to the basal musteloid condition. Within Procyonidae, similar patterns of variation are present, and may be associated with increased arboreality in certain taxa. Thus, brain shape derived from endocasts may be used to test for phylogenetic signal and preliminary analyses suggest an association with behavior and ecology.
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Affiliation(s)
- Heather E Ahrens
- Center for Functional Anatomy and Evolution, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA
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Orliac MJ, Ladevèze S, Gingerich PD, Lebrun R, Smith T. Endocranial morphology of Palaeocene Plesiadapis tricuspidens and evolution of the early primate brain. Proc Biol Sci 2014; 281:20132792. [PMID: 24573845 PMCID: PMC3953834 DOI: 10.1098/rspb.2013.2792] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2013] [Accepted: 02/03/2014] [Indexed: 11/12/2022] Open
Abstract
Expansion of the brain is a key feature of primate evolution. The fossil record, although incomplete, allows a partial reconstruction of changes in primate brain size and morphology through time. Palaeogene plesiadapoids, closest relatives of Euprimates (or crown-group primates), are crucial for understanding early evolution of the primate brain. However, brain morphology of this group remains poorly documented, and major questions remain regarding the initial phase of euprimate brain evolution. Micro-CT investigation of the endocranial morphology of Plesiadapis tricuspidens from the Late Palaeocene of Europe--the most complete plesiadapoid cranium known--shows that plesiadapoids retained a very small and simple brain. Plesiadapis has midbrain exposure, and minimal encephalization and neocorticalization, making it comparable with that of stem rodents and lagomorphs. However, Plesiadapis shares a domed neocortex and downwardly shifted olfactory-bulb axis with Euprimates. If accepted phylogenetic relationships are correct, then this implies that the euprimate brain underwent drastic reorganization during the Palaeocene, and some changes in brain structure preceded brain size increase and neocortex expansion during evolution of the primate brain.
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Affiliation(s)
- Maeva J. Orliac
- Institut des Sciences de l'Evolution (ISEM UMR 5554), Université Montpellier 2, CC 064, Place Eugène Bataillon, 34270 Montpellier Cedex 05, France
| | - Sandrine Ladevèze
- Muséum national d'Histoire naturelle, UMR 7207 CR2P CNRS/MNHN/UPMC, 8 rue Buffon, CP 38, 75231 Paris Cedex 05, France
| | - Philip D. Gingerich
- Museum of Paleontology, The University of Michigan, Ann Arbor, MI 48109-1079, USA
| | - Renaud Lebrun
- Institut des Sciences de l'Evolution (ISEM UMR 5554), Université Montpellier 2, CC 064, Place Eugène Bataillon, 34270 Montpellier Cedex 05, France
| | - Thierry Smith
- O.D. Earth & History of life, Royal Belgian Institute of Natural History, 29 rue Vautier, 1000 Brussels, Belgium
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Castanhinha R, Araújo R, Júnior LC, Angielczyk KD, Martins GG, Martins RMS, Chaouiya C, Beckmann F, Wilde F. Bringing dicynodonts back to life: paleobiology and anatomy of a new emydopoid genus from the Upper Permian of Mozambique. PLoS One 2013; 8:e80974. [PMID: 24324653 PMCID: PMC3852158 DOI: 10.1371/journal.pone.0080974] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Accepted: 10/04/2013] [Indexed: 11/19/2022] Open
Abstract
Dicynodontia represent the most diverse tetrapod group during the Late Permian. They survived the Permo-Triassic extinction and are central to understanding Permo-Triassic terrestrial ecosystems. Although extensively studied, several aspects of dicynodont paleobiology such as, neuroanatomy, inner ear morphology and internal cranial anatomy remain obscure. Here we describe a new dicynodont (Therapsida, Anomodontia) from northern Mozambique: Niassodon mfumukasi gen. et sp. nov. The holotype ML1620 was collected from the Late Permian K5 formation, Metangula Graben, Niassa Province northern Mozambique, an almost completely unexplored basin and country for vertebrate paleontology. Synchrotron radiation based micro-computed tomography (SRµCT), combined with a phylogenetic analysis, demonstrates a set of characters shared with Emydopoidea. All individual bones were digitally segmented allowing a 3D visualization of each element. In addition, we reconstructed the osseous labyrinth, endocast, cranial nerves and vasculature. The brain is narrow and the cerebellum is broader than the forebrain, resembling the conservative, "reptilian-grade" morphology of other non-mammalian therapsids, but the enlarged paraflocculi occupy the same relative volume as in birds. The orientation of the horizontal semicircular canals indicates a slightly more dorsally tilted head posture than previously assumed in other dicynodonts. In addition, synchrotron data shows a secondary center of ossification in the femur. Thus ML1620 represents, to our knowledge, the oldest fossil evidence of a secondary center of ossification, pushing back the evolutionary origins of this feature. The fact that the specimen represents a new species indicates that the Late Permian tetrapod fauna of east Africa is still incompletely known.
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Affiliation(s)
- Rui Castanhinha
- Instituto Gulbenkian de Ciência, Oeiras, Portugal
- Museu da Lourinhã, Lourinhã, Portugal
| | - Ricardo Araújo
- Museu da Lourinhã, Lourinhã, Portugal
- Huffington Department of Earth Sciences, Southern Methodist University, Dallas, Texas, United States of America
| | | | - Kenneth D. Angielczyk
- Integrative Research Center, Field Museum of Natural History, Chicago, Illinois, United States of America
| | - Gabriel G. Martins
- Centro de Biologia Ambiental, Faculdade de Ciências, Universidade de Lisboa, Lisboa, Portugal
| | - Rui M. S. Martins
- Museu da Lourinhã, Lourinhã, Portugal
- Campus Tecnológico e Nuclear, Instituto Superior Técnico, Bobadela, Portugal
- Centro de Investigação em Materiais, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal
- Centro de Física Nuclear da Universidade de Lisboa, Lisboa, Portugal
| | | | | | - Fabian Wilde
- Helmholtz-Zentrum Geesthacht, Geesthacht, Germany
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Racicot RA, Colbert MW. Morphology and Variation in Porpoise (Cetacea: Phocoenidae) Cranial Endocasts. Anat Rec (Hoboken) 2013; 296:979-92. [DOI: 10.1002/ar.22704] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Accepted: 03/20/2013] [Indexed: 11/09/2022]
Affiliation(s)
- Rachel A. Racicot
- Department of Geology and Geophysics; Yale University; New Haven Connecticut
| | - Matthew W. Colbert
- Jackson School of Geosciences; The University of Texas at Austin; Austin Texas
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Benoit J, Crumpton N, Mérigeaud S, Tabuce R. A Memory Already like an Elephant's? The Advanced Brain Morphology of the Last Common Ancestor of Afrotheria (Mammalia). BRAIN, BEHAVIOR AND EVOLUTION 2013; 81:154-69. [DOI: 10.1159/000348481] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Accepted: 01/24/2013] [Indexed: 11/19/2022]
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Averianov AO, Martin T, Lopatin AV. A new phylogeny for basal Trechnotheria and Cladotheria and affinities of South American endemic Late Cretaceous mammals. Naturwissenschaften 2013; 100:311-26. [PMID: 23494201 DOI: 10.1007/s00114-013-1028-3] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Revised: 02/22/2013] [Accepted: 02/26/2013] [Indexed: 11/25/2022]
Abstract
The endemic South American mammals Meridiolestida, considered previously as dryolestoid cladotherians, are found to be non-cladotherian trechnotherians related to spalacotheriid symmetrodontans based on a parsimony analysis of 137 morphological characters among 44 taxa. Spalacotheriidae is the sister taxon to Meridiolestida, and the latter clade is derived from a primitive spalacolestine that migrated to South America from North America at the beginning of the Late Cretaceous. Meridiolestida survived until the early Paleocene (Peligrotherium) and early Miocene (Necrolestes) in South America, and their extinction is probably linked to the increasing competition with metatherian and eutherian tribosphenic mammals. The clade Meridiolestida plus Spalacotheriidae is the sister taxon to Cladotheria and forms a new clade Alethinotheria. Alethinotheria and its sister taxon Zhangheotheria, new clade (Zhangheotheriidae plus basal taxa), comprise Trechnotheria. Cladotheria is divided into Zatheria (plus stem taxa, including Amphitherium) and Dryolestida, including Dryolestidae and a paraphyletic array of basal dryolestidans (formerly classified as "Paurodontidae"). The South American Vincelestes and Groebertherium are basal dryolestidans.
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Affiliation(s)
- Alexander O Averianov
- Zoological Institute of the Russian Academy of Sciences, Universitetskaya nab. 1, 199034 Saint Petersburg, Russia.
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42
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LUO ZHEXI, RUF IRINA, MARTIN THOMAS. The petrosal and inner ear of the Late Jurassic cladotherian mammalDryolestes leiriensisand implications for ear evolution in therian mammals. Zool J Linn Soc 2012. [DOI: 10.1111/j.1096-3642.2012.00852.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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43
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KSEPKA DANIELT, BALANOFF AMYM, WALSH STIG, REVAN ARIEL, HO AMY. Evolution of the brain and sensory organs in Sphenisciformes: new data from the stem penguin Paraptenodytes antarcticus. Zool J Linn Soc 2012. [DOI: 10.1111/j.1096-3642.2012.00835.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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44
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Orliac MJ, Gilissen E. Virtual endocranial cast of earliest Eocene Diacodexis (Artiodactyla, Mammalia) and morphological diversity of early artiodactyl brains. Proc Biol Sci 2012; 279:3670-7. [PMID: 22764165 DOI: 10.1098/rspb.2012.1156] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The study of brain evolution, particularly that of the neocortex, is of primary interest because it directly relates to how behavioural variations arose both between and within mammalian groups. Artiodactyla is one of the most diverse mammalian clades. However, the first 10 Myr of their brain evolution has remained undocumented so far. Here, we used high-resolution X-ray computed tomography to investigate the endocranial cast of Diacodexis ilicis of earliest Eocene age. Its virtual reconstruction provides unprecedented access to both metric parameters and fine anatomy of the most complete endocast of the earliest artiodactyl. This picture is assessed in a broad comparative context by reconstructing endocasts of 14 other Early and Middle Eocene representatives of basal artiodactyls, allowing the tracking of the neocortical structure of artiodactyls back to its simplest pattern. We show that the earliest artiodactyls share a simple neocortical pattern, so far never observed in other ungulates, with an almond-shaped gyrus instead of parallel sulci as previously hypothesized. Our results demonstrate that artiodactyls experienced a tardy pulse of encephalization during the Late Neogene, well after the onset of cortical complexity increase. Comparisons with Eocene perissodactyls show that the latter reached a high level of cortical complexity earlier than the artiodactyls.
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Affiliation(s)
- M J Orliac
- ISE-M, Université Montpellier2, Place Eugène Bataillon, 34095 Montpellier cedex 05, France.
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45
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Silcox MT, Benham AE, Bloch JI. Endocasts of Microsyops (Microsyopidae, Primates) and the evolution of the brain in primitive primates. J Hum Evol 2010; 58:505-21. [PMID: 20444495 DOI: 10.1016/j.jhevol.2010.03.008] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2009] [Revised: 03/18/2010] [Accepted: 03/23/2010] [Indexed: 11/24/2022]
Abstract
We describe a virtual endocast produced from ultra high resolution X-ray computed tomography (CT) data for the microsyopid, Microsyops annectens (middle Eocene, Wyoming). It is the most complete and least distorted endocast known for a plesiadapiform primate and because of the relatively basal position of Microsyopidae, has particular importance to reconstructing primitive characteristics for Primates. Cranial capacity is estimated at 5.9 cm(3), yielding encephalization quotients (EQ) of 0.26-0.39 (Jerison's equation) and 0.32-0.52 (Eisenberg's equation), depending on the body mass estimate. Even the lowest EQ estimate for M. annectens is higher than that for Plesiadapis cookei, while the range of estimates overlaps with that of Ignacius graybullianus and with the lower end of the range of estimates for fossil euprimates. As in other plesiadapiforms, the olfactory bulbs of M. annectens are large. The cerebrum does not extend onto the cerebellum or form a ventrally protruding temporal lobe with a clear temporal pole, suggesting less development of the visual sense and a greater emphasis on olfaction than in euprimates. Contrasts between the virtual endocast of M. annectens, and both a natural endocast of the same species and a partial endocast from the earlier-occurring Microsyops sp., cf. Microsyops elegans, suggest that the coverage of the caudal colliculi by the cerebrum evolved within the Microsyops lineage. This implies that microsyopids expanded their cerebra and perhaps evolved an improved visual sense independent of euprimates. With a growing body of data on the morphology of the brain in primitive primates, it is becoming clear that many of the characteristics of the brain common to euprimates evolved after the divergence of stem primates from other euarchontans and likely in parallel in different lineages. These new data suggest a different model for the ancestors of euprimates than has been assumed based on the anatomy of the brain in visually specialized diurnal tree shrews.
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Affiliation(s)
- Mary T Silcox
- Department of Anthropology, University of Winnipeg, 515 Portage Avenue, Winnipeg, MB R3B 2E9, Canada.
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Virtual endocast of Ignacius graybullianus (Paromomyidae, Primates) and brain evolution in early primates. Proc Natl Acad Sci U S A 2009; 106:10987-92. [PMID: 19549862 DOI: 10.1073/pnas.0812140106] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Extant primates are distinctive among mammals in having relatively large brains. As stem primates, Paleogene plesiadapiforms provide direct information relevant to the earliest stages in the evolution of this characteristic. Here we describe a virtual endocast reconstructed from ultra high resolution X-ray computed tomography data for the paromomyid plesiadapiform Ignacius graybullianus (USNM 421608) from the early Eocene of Wyoming. This represents the most complete endocast known for a stem primate, allowing for an unprecedented study of both size and fine details of anatomy. Relative to fossil and extant euprimates, I. graybullianus had large olfactory lobes, but less caudal development of the cerebrum and a poorly demarcated temporal lobe, suggesting more emphasis on olfaction and a less well developed visual system. Although its brain was small compared to those of extant primates, the encephalization quotient of I. graybullianus is higher than that calculated for Paleocene Plesiadapis cookei and overlaps the lower portion of the range documented for fossil euprimates. Comparison to the basal gliroid Rhombomylus suggests that early primates exhibited some expansion of the cerebrum compared to their ancestors. The relatively small brain size of I. graybullianus, an arboreal frugivore, implies that neither arboreality nor frugivory was primarily responsible for the expanded brains of modern primates. However, the contrasts in features related to the visual system between I. graybullianus and fossil and extant euprimates suggest that improvements to these portions of the brain contributed to increases in brain size within Euprimates.
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Asher RJ, Geisler JH, Sánchez-Villagra MR. Morphology, paleontology, and placental mammal phylogeny. Syst Biol 2008; 57:311-7. [PMID: 18432551 DOI: 10.1080/10635150802033022] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Affiliation(s)
- Robert J Asher
- Department of Zoology, University of Cambridge, Downing Street, UK
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Macrini TE, Rowe T, Vandeberg JL. Cranial endocasts from a growth series ofMonodelphis domestica (Didelphidae, Marsupialia): A study of individual and ontogenetic variation. J Morphol 2007; 268:844-65. [PMID: 17626259 DOI: 10.1002/jmor.10556] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Intraspecific variation (e.g., ontogenetic, individual, sexual dimorphic) is rarely examined among cranial endocasts (infillings of the braincase cavity) because of the difficulty in obtaining multiple specimens of a species, particularly fossil taxa. We extracted digital cranial endocasts from CT scans of a growth series of skulls of Monodelphis domestica, the gray short-tailed opossum, as a preliminary assessment of the amount of intraspecific variation in mammalian endocranial morphology. The goals of this study were 1) to provide an anatomical description to document developmental changes in endocranial morphology of M. domestica and 2) to examine ontogenetic and individual variation with respect to phylogenetic characters of endocranial cavities that are known to be variable between different mammalian taxa. In this study, "ontogenetic variation" refers to variation between specimens of different ages whereas "individual variation" (i.e., polymorphism) is restricted to variation between specimens of comparable age. Aside from size, changes in shape account for the greatest amount of morphological variation between the endocasts of different ages. Endocast length, width, and volume increase with age for the growth series. Relative olfactory bulb cast size increases with age in the growth series, but the relative size of the parafloccular casts shows a slight negative allometric trend through ontogeny. More than one-third of the phylogenetic characters of the endocranial cavity we examined showed some sort of variation (ontogenetic, individual, or both). This suggests that although endocasts are potentially informative for systematics, both ontogenetic and individual variation affect how endocranial characters are scored for phylogenetic analysis. Further studies such as this are necessary to determine the taxonomic extent of significant intraspecific variation of these endocranial characters.
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Affiliation(s)
- Thomas E Macrini
- Department of Mammalogy, American Museum of Natural History, New York, New York 10024, USA.
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