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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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2
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Lauters P, Vercauteren M, Godefroit P. Endocasts of ornithopod dinosaurs: Comparative anatomy. PROGRESS IN BRAIN RESEARCH 2023; 275:1-23. [PMID: 36841565 DOI: 10.1016/bs.pbr.2022.10.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Ornithopod dinosaurs were a successful group before they became extinct at the end of the Cretaceous. They were present on every continent, though they were rare in the Southern Hemisphere. We present the results of our work on the brain of these dinosaurs as an attempt to determine which evolutionary trends affected it. Old and new technologies allow us to peer into the skull of long extinct animals and retrieve information about their brain. First we provide a short description of the brain of ornithopod dinosaurs from Europe and Asia, then we sum up the characteristics that can be gathered from it. The presence of valleculae helps us to assess the actual size of the brain with more confidence. The olfactory peduncles are large and these animals had a good sense of smell. There is a trend toward an increase in the size of the cerebral hemispheres, and a more straight-lined brain. The latter can be the result of the ontogeny and the size achieved by the adult animal on the development of the brain. Other characteristics, like the development of the cerebral hemispheres and the encephalization quotient, allude to Hadrosauridae having had cognitive abilities more developed than previously assumed. This is in adequacy with other data from the physical characteristics (e.g., crests) and the social life (e.g., living in herds, communal nests) of these dinosaurs, which denote high and complex behaviors like care for their young, sexual courtship, and gregariousness.
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Affiliation(s)
- Pascaline Lauters
- Université Libre de Bruxelles, Brussels, Belgium; Royal Belgian Institute of Natural Sciences, Brussels, Belgium.
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3
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Wible JR. The history and homology of the os paradoxum or dumb-bell-shaped bone of the platypus Ornithorhynchus anatinus (Mammalia, Monotremata). VERTEBRATE ZOOLOGY 2022. [DOI: 10.3897/vz.72.e80508] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Abstract
The os paradoxum or dumb-bell-shaped bone is a paired bone occurring in the middle of the specialized bill of the platypus Ornithorhynchus anatinus. It has been variously considered as a neomorph of the platypus, as the homologue of the paired vomer of sauropsids, or as a part of the paired premaxillae. A review of the near 200-year history of this element strongly supports the os paradoxum as a remnant of the medial palatine processes of the premaxillae given its ontogenetic continuity with the premaxillae and association with the vomeronasal organ and cartilage, incisive foramen, and cartilaginous nasal septum. In conjunction with this hypothesis, homologies of the unpaired vomer of extant mammals and the paired vomer of extant sauropsids are also supported. These views are reinforced with observations from CT scans of O. anatinus, the Miocene ornithorhynchid Obdurodon dicksoni, and the extant didelphid marsupial Didelphis marsupialis. At the choanae, Obdurodon has what appears to be a separate parasphenoid bone unknown in extant monotremes.
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4
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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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5
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Ferreira JD, Dozo MT, de Moura Bubadué J, Kerber L. Morphology and postnatal ontogeny of the cranial endocast and paranasal sinuses of capybara (Hydrochoerus hydrochaeris), the largest living rodent. J Morphol 2021; 283:66-90. [PMID: 34775628 DOI: 10.1002/jmor.21428] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Revised: 11/04/2021] [Accepted: 11/07/2021] [Indexed: 01/22/2023]
Abstract
Recent studies have analyzed and described the endocranial cavities of caviomorph rodents. However, no study has documented the changes in the morphology and relative size of such cavities during ontogeny. Expecting to contribute to the discussion of the endocranial spaces of extinct caviomorphs, we aimed to characterize the cranial endocast morphology and paranasal sinuses of the largest living rodent, Hydrochoerus hydrochaeris, by focusing on its ontogenetic growth patterns. We analyzed 12 specimens of different ontogenetic stages and provided a comparison with other cavioids. Our study demonstrates that the adult cranial endocast of H. hydrochaeris is characterized by olfactory bulbs with an irregular shape, showing an elongated olfactory tract without a clear circular fissure, a marked temporal region that makes the endocast with rhombus outline, and gyrencephaly. Some of these traits change as the brain grows. The cranial pneumatization is present in the frontal and lacrimal bones. We identified two recesses (frontal and lacrimal) and one sinus (frontal). These pneumatic cavities increase their volume as the cranium grows, covering the cranial region of the cranial endocast. The encephalization quotient was calculated for each specimen, demonstrating that it decreases as the individual grows, being much higher in younger specimens than in adults. Our results show that the ontogenetic stage can be a confounding factor when it comes to the general patterns of encephalization of extinct rodents, reinforcing the need for paleobiologists to take the age of the specimens into account in future studies on this subject to avoid age-related biases.
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Affiliation(s)
- José D Ferreira
- Programa de Pós-Graduação em Biodiversidade Animal, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, Brazil.,Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, Brazil
| | - Maria Teresa Dozo
- Instituto Patagónico de Geología y Paleontología, CCT CONICET-CENPAT, Puerto Madryn, Argentina
| | - Jamile de Moura Bubadué
- Laboratório de Ciências Ambientais, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brazil
| | - Leonardo Kerber
- Programa de Pós-Graduação em Biodiversidade Animal, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, Brazil.,Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, Brazil.,Museu Paraense Emílio Goeldi, Coordenação de Ciências da Terra e Ecologia, Belém, Brazil
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6
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Gutarra S, Rahman IA. The locomotion of extinct secondarily aquatic tetrapods. Biol Rev Camb Philos Soc 2021; 97:67-98. [PMID: 34486794 DOI: 10.1111/brv.12790] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 08/14/2021] [Accepted: 08/18/2021] [Indexed: 02/06/2023]
Abstract
The colonisation of freshwater and marine ecosystems by land vertebrates has repeatedly occurred in amphibians, reptiles, birds and mammals over the course of 300 million years. Functional interpretations of the fossil record are crucial to understanding the forces shaping these evolutionary transitions. Secondarily aquatic tetrapods have acquired a suite of anatomical, physiological and behavioural adaptations to locomotion in water. However, much of this information is lost for extinct clades, with fossil evidence often restricted to osteological data and a few extraordinary specimens with soft tissue preservation. Traditionally, functional morphology in fossil secondarily aquatic tetrapods was investigated through comparative anatomy and correlation with living functional analogues. However, in the last two decades, biomechanics in palaeobiology has experienced a remarkable methodological shift. Anatomy-based approaches are increasingly rigorous, informed by quantitative techniques for analysing shape. Moreover, the incorporation of physics-based methods has enabled objective tests of functional hypotheses, revealing the importance of hydrodynamic forces as drivers of evolutionary innovation and adaptation. Here, we present an overview of the latest research on the locomotion of extinct secondarily aquatic tetrapods, with a focus on amniotes, highlighting the state-of-the-art experimental approaches used in this field. We discuss the suitability of these techniques for exploring different aspects of locomotory adaptation, analysing their advantages and limitations and laying out recommendations for their application, with the aim to inform future experimental strategies. Furthermore, we outline some unexplored research avenues that have been successfully deployed in other areas of palaeobiomechanical research, such as the use of dynamic models in feeding mechanics and terrestrial locomotion, thus providing a new methodological synthesis for the field of locomotory biomechanics in extinct secondarily aquatic vertebrates. Advances in imaging technology and three-dimensional modelling software, new developments in robotics, and increased availability and awareness of numerical methods like computational fluid dynamics make this an exciting time for analysing form and function in ancient vertebrates.
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Affiliation(s)
- Susana Gutarra
- School of Earth Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol, BS8 1TQ, U.K.,Department of Earth Sciences, the Natural History Museum, Cromwell Road, London, U.K
| | - Imran A Rahman
- Department of Earth Sciences, the Natural History Museum, Cromwell Road, London, U.K.,Oxford University Museum of Natural History, Parks Road, Oxford, OX1 3PW, U.K
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7
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MacPhee R, Del Pino SH, Kramarz A, Forasiepi AM, Bond M, Sulser RB. Cranial Morphology and Phylogenetic Relationships of Trigonostylops wortmani, an Eocene South American Native Ungulate. BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY 2021. [DOI: 10.1206/0003-0090.449.1.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
- R.D.E. MacPhee
- Department of Mammalogy/Vertebrate Zoology and Richard Gilder Graduate School, American Museum of Natural History
| | | | - Alejandro Kramarz
- Sección Paleontología de Vertebrados, Museo Argentino de Ciencias Naturales Bernardino Rivadavia, CONICET, Buenos Aires, Argentina
| | | | - Mariano Bond
- Departamento Científico de Paleontología Vertebrados, Museo de La Plata, Paseo del Bosque s/n, 1900 La Plata, Argentina
| | - R. Benjamin Sulser
- Department of Mammalogy/Vertebrate Zoology and Richard Gilder Graduate School, American Museum of Natural History
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8
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Smaers JB, Rothman RS, Hudson DR, Balanoff AM, Beatty B, Dechmann DKN, de Vries D, Dunn JC, Fleagle JG, Gilbert CC, Goswami A, Iwaniuk AN, Jungers WL, Kerney M, Ksepka DT, Manger PR, Mongle CS, Rohlf FJ, Smith NA, Soligo C, Weisbecker V, Safi K. The evolution of mammalian brain size. SCIENCE ADVANCES 2021; 7:7/18/eabe2101. [PMID: 33910907 PMCID: PMC8081360 DOI: 10.1126/sciadv.abe2101] [Citation(s) in RCA: 65] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 03/10/2021] [Indexed: 05/08/2023]
Abstract
Relative brain size has long been considered a reflection of cognitive capacities and has played a fundamental role in developing core theories in the life sciences. Yet, the notion that relative brain size validly represents selection on brain size relies on the untested assumptions that brain-body allometry is restrained to a stable scaling relationship across species and that any deviation from this slope is due to selection on brain size. Using the largest fossil and extant dataset yet assembled, we find that shifts in allometric slope underpin major transitions in mammalian evolution and are often primarily characterized by marked changes in body size. Our results reveal that the largest-brained mammals achieved large relative brain sizes by highly divergent paths. These findings prompt a reevaluation of the traditional paradigm of relative brain size and open new opportunities to improve our understanding of the genetic and developmental mechanisms that influence brain size.
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Affiliation(s)
- J B Smaers
- Department of Anthropology, Stony Brook University, Stony Brook, NY 11794, USA.
- Division of Anthropology, American Museum of Natural History, New York, NY 10024, USA
| | - R S Rothman
- Interdepartmental Doctoral Program in Anthropological Sciences, Stony Brook University, Stony Brook, NY 11794, USA
| | - D R Hudson
- Interdepartmental Doctoral Program in Anthropological Sciences, Stony Brook University, Stony Brook, NY 11794, USA
| | - A M Balanoff
- Department of Psychological and Brain Sciences Johns Hopkins University, Baltimore, MD 21218, USA
- Division of Paleontology, American Museum of Natural History, New York, NY 10024, USA
| | - B Beatty
- NYIT College of Osteopathic Medicine, Old Westbury, NY 11568, USA
- United States National Museum, Smithsonian Institution, Washington, DC 20560, USA
| | - D K N Dechmann
- Department of Migration, Max-Planck Institute of Animal Behavior, 78315 Radolfzell, Germany
- Department of Biology, University of Konstanz, 78464 Konstanz, Germany
| | - D de Vries
- Ecosystems and Environment Research Centre, School of Science, Engineering and Environment, University of Salford, Manchester M5 4WX, UK
| | - J C Dunn
- Division of Biological Anthropology, University of Cambridge, Cambridge CB2 3QG, UK
- Behavioral Ecology Research Group, Anglia Ruskin University, Cambridge CB1 1PT, UK
- Department of Cognitive Biology, University of Vienna, Vienna 1090, Austria
| | - J G Fleagle
- Department of Anatomical Sciences, Stony Brook University, Stony Brook, NY 11794, USA
| | - C C Gilbert
- NYIT College of Osteopathic Medicine, Old Westbury, NY 11568, USA
- Department of Anthropology, Hunter College, New York, NY 10065, USA
- PhD Program in Anthropology, Graduate Center of the City University of New York, 365 Fifth Avenue, New York, NY 10016, USA
- New York Consortium in Evolutionary Primatology, New York, NY 10065, USA
| | - A Goswami
- Department of Life Sciences, Natural History Museum, London SW7 5BD, UK
| | - A N Iwaniuk
- Department of Neuroscience, University of Lethbridge, Lethbridge, AB T1K-3M4, Canada
| | - W L Jungers
- Department of Anatomical Sciences, Stony Brook University, Stony Brook, NY 11794, USA
- Association Vahatra, BP 3972, Antananarivo 101, Madagascar
| | - M Kerney
- Behavioral Ecology Research Group, Anglia Ruskin University, Cambridge CB1 1PT, UK
| | - D T Ksepka
- Bruce Museum, Greenwich, CT 06830, USA
- Department of Ornithology, American Museum of Natural History, New York, NY 10024, USA
- Division of Science and Education, Field Museum of Natural History, Chicago, IL 60605, USA
- Department of Paleobiology, Smithsonian Institution, Washington, DC 20013, USA
| | - P R Manger
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - C S Mongle
- Division of Anthropology, American Museum of Natural History, New York, NY 10024, USA
- Interdepartmental Doctoral Program in Anthropological Sciences, Stony Brook University, Stony Brook, NY 11794, USA
- Turkana Basin Institute, Stony Brook University, Stony Brook, NY 11794, USA
| | - F J Rohlf
- Department of Anthropology, Stony Brook University, Stony Brook, NY 11794, USA
| | - N A Smith
- Division of Science and Education, Field Museum of Natural History, Chicago, IL 60605, USA
- Campbell Geology Museum, Clemson University, Clemson, SC 29634, USA
| | - C Soligo
- Department of Anthropology, University College London, London WC1H 0BW, UK
| | - V Weisbecker
- College of Science and Engineering, Flinders University, Bedford Park, SA 5042, Australia
| | - K Safi
- Department of Migration, Max-Planck Institute of Animal Behavior, 78315 Radolfzell, Germany
- Department of Biology, University of Konstanz, 78464 Konstanz, Germany
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9
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Bino G, Kingsford RT, Archer M, Connolly JH, Day J, Dias K, Goldney D, Gongora J, Grant T, Griffiths J, Hawke T, Klamt M, Lunney D, Mijangos L, Munks S, Sherwin W, Serena M, Temple-Smith P, Thomas J, Williams G, Whittington C. The platypus: evolutionary history, biology, and an uncertain future. J Mammal 2019; 100:308-327. [PMID: 31043761 PMCID: PMC6479513 DOI: 10.1093/jmammal/gyz058] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 02/25/2019] [Indexed: 12/21/2022] Open
Abstract
The platypus (Ornithorhynchus anatinus) is one of the world's most evolutionarily distinct mammals, one of five extant species of egg-laying mammals, and the only living species within the family Ornithorhynchidae. Modern platypuses are endemic to eastern mainland Australia, Tasmania, and adjacent King Island, with a small introduced population on Kangaroo Island, South Australia, and are widely distributed in permanent river systems from tropical to alpine environments. Accumulating knowledge and technological advancements have provided insights into many aspects of its evolutionary history and biology but have also raised concern about significant knowledge gaps surrounding distribution, population sizes, and trends. The platypus' distribution coincides with many of Australia's major threatening processes, including highly regulated and disrupted rivers, intensive habitat destruction, and fragmentation, and they were extensively hunted for their fur until the early 20th century. Emerging evidence of local population declines and extinctions identifies that ecological thresholds have been crossed in some populations and, if threats are not addressed, the species will continue to decline. In 2016, the IUCN Red Listing for the platypus was elevated to "Near Threatened," but the platypus remains unlisted on threatened species schedules of any Australian state, apart from South Australia, or nationally. In this synthesis, we review the evolutionary history, genetics, biology, and ecology of this extraordinary mammal and highlight prevailing threats. We also outline future research directions and challenges that need to be met to help conserve the species.
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Affiliation(s)
- Gilad Bino
- Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Richard T Kingsford
- Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Michael Archer
- Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Joanne H Connolly
- School of Animal and Veterinary Sciences, Charles Sturt University, Wagga Wagga, New South Wales, Australia.,Graham Centre for Agricultural Innovation, Wagga Wagga, New South Wales, Australia
| | - Jenna Day
- Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, Sydney, New South Wales, Australia
| | - Kimberly Dias
- Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, Sydney, New South Wales, Australia
| | - David Goldney
- Charles Sturt University, Wagga Wagga, New South Wales, Australia
| | - Jaime Gongora
- Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, Sydney, New South Wales, Australia
| | - Tom Grant
- Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | | | - Tahneal Hawke
- Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Melissa Klamt
- Biological Sciences, Monash University, Melbourne, Victoria, Australia
| | - Daniel Lunney
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia.,Office of Environment and Heritage, Hurstville, New South Wales, Australia
| | - Luis Mijangos
- Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Sarah Munks
- School of Biological Sciences, University of Tasmania, Tasmania, Australia.,Forest Practices Authority, Hobart, Tasmania, Australia
| | - William Sherwin
- Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Melody Serena
- Australian Platypus Conservancy, Wiseleigh, Victoria, Australia
| | - Peter Temple-Smith
- Department of Obstetrics and Gynaecology, Southern Clinical School, Monash University, Clayton, Victoria, Australia
| | | | - Geoff Williams
- Australian Platypus Conservancy, Wiseleigh, Victoria, Australia
| | - Camilla Whittington
- Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, Sydney, New South Wales, Australia.,School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia
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10
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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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11
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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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12
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Triviño LN, Albino AM, Dozo MT, Williams JD. First Natural Endocranial Cast of a Fossil Snake (Cretaceous of Patagonia, Argentina). Anat Rec (Hoboken) 2017; 301:9-20. [DOI: 10.1002/ar.23686] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 03/20/2017] [Accepted: 03/23/2017] [Indexed: 11/09/2022]
Affiliation(s)
- Laura N. Triviño
- CONICET, Sección Herpetología; Museo de La Plata, Universidad Nacional de La Plata; Paseo del Bosque s/n, La Plata B1900FWA Argentina
| | - Adriana M. Albino
- CONICET, Departamento de Biología; Universidad Nacional de Mar del Plata; Funes 3250, Mar del Plata B7602AYJ Argentina
| | - María T. Dozo
- CONICET, Centro Nacional Patagónico; Instituto Patagónico de Geología y Paleontología; Boulevard Brown 2915, Puerto, Madryn U9120ACD Argentina
| | - Jorge D. Williams
- CONICET, Sección Herpetología; Museo de La Plata, Universidad Nacional de La Plata; Paseo del Bosque s/n, La Plata B1900FWA Argentina
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13
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Arbez T, Dahoumane A, Steyer JS. Exceptional endocranium and middle ear of Stanocephalosaurus (Temnospondyli: Capitosauria) from the Triassic of Algeria revealed by micro-CT scan, with new functional interpretations of the hearing system. Zool J Linn Soc 2017. [DOI: 10.1093/zoolinnean/zlw007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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14
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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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Asahara M, Koizumi M, Macrini TE, Hand SJ, Archer M. Comparative cranial morphology in living and extinct platypuses: Feeding behavior, electroreception, and loss of teeth. SCIENCE ADVANCES 2016; 2:e1601329. [PMID: 27757425 PMCID: PMC5061491 DOI: 10.1126/sciadv.1601329] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/12/2016] [Accepted: 09/08/2016] [Indexed: 06/06/2023]
Abstract
The modern platypus, Ornithorhynchus anatinus, has an eye structure similar to aquatic mammals; however, platypuses also have a "sixth sense" associated with the bill electro- and mechanoreception that they use without opening their eyes underwater. We hypothesize that Ornithorhynchus and the Miocene taxon Obdurodon have different sensory capacities, which may have resulted from differences in foraging behavior. To estimate differences in foraging, sensory systems, and anatomical divergence between these monotremes, we compared their skull morphologies. Results indicate that the bill of Obdurodon is more dorsally deflected than that of Ornithorhynchus, suggesting a pelagic foraging behavior in Obdurodon compared to the bottom-feeding behavior in Ornithorhynchus. The infraorbital foramen of Obdurodon, through which the maxillary nerve passes sensory data from the bill to the brain, is relatively less developed than that of Ornithorhynchus. Whereas bill-focused sensory perception was likely shared among Mesozoic monotremes, the highly developed electrosensory system of Ornithorhynchus may represent an adaptation to foraging in cloudy water. Computed tomography imagery indicates that the enlarged infraorbital canal of Ornithorhynchus restricts the space available for maxillary tooth roots. Hence, loss of functional teeth in Ornithorhynchus may possibly have resulted from a shift in foraging behavior and coordinate elaboration of the electroreceptive sensory system. Well-developed electroreceptivity in monotremes is known at least as far back as the early Cretaceous; however, there are differences in the extent of elaboration of the feature among members of the ornithorhynchid lineage.
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Affiliation(s)
- Masakazu Asahara
- College of Liberal Arts and Sciences, Mie University, Kurima-machiya-cho 1577, Tsu, Mie 514-8507, Japan
| | - Masahiro Koizumi
- Department of Acupuncture and Moxibustion, Tokyo Ariake University of Medical and Health Sciences, 2-9-1 Ariake, Koto-ku, Tokyo 135-0063, Japan
| | - Thomas E. Macrini
- Department of Biological Sciences, St. Mary’s University, One Camino Santa Maria, San Antonio, TX 78228, USA
| | - Suzanne J. Hand
- Palaeontology, Geobiology and Earth Archives Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Michael Archer
- Palaeontology, Geobiology and Earth Archives Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
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16
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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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17
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Thiery G, Ducrocq S. Endocasts and brain evolution in Anthracotheriidae (Artiodactyla, Hippopotamoidea). J Anat 2016; 227:277-85. [PMID: 26278931 DOI: 10.1111/joa.12348] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/09/2015] [Indexed: 11/30/2022] Open
Abstract
Anthracotheres are a fossil family of 'Suiformes' from the Old World, North and Central America. They are known from the middle Eocene to the late Pliocene, and are suggested to be the stem group of Hippopotamidae. Yet, their soft anatomy remains poorly known. In this study we describe the virtual endocast of the late Oligocene anthracothere Microbunodon minimum, reconstructed using microtomography, as well as the natural endocast of Merycopotamus medioximus from the late Miocene. These are the first anthracothere endocasts ever described. Particular attention is given to the relative proportions of the brain, the neocortex, the cerebellum and the olfactory bulbs. The 'backward shift' of the pituitary of M. minimum, and the possible presence of a K lobe in M. medioximus, is discussed. Previous statements that some endocranial characters were subject to convergence among mammals are also corroborated.
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Affiliation(s)
- Ghislain Thiery
- iPHEP: Institut de Paléoprimatologie, Paléontologie Humaine: Evolution et Paléoenvironnements, UMR CNRS 7262, TSA 51106, 6 rue Michel Brunet, 86073 Poitiers, France
| | - Stéphane Ducrocq
- iPHEP: Institut de Paléoprimatologie, Paléontologie Humaine: Evolution et Paléoenvironnements, UMR CNRS 7262, TSA 51106, 6 rue Michel Brunet, 86073 Poitiers, France
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Rowe TB, Shepherd GM. Role of ortho-retronasal olfaction in mammalian cortical evolution. J Comp Neurol 2016; 524:471-95. [PMID: 25975561 PMCID: PMC4898483 DOI: 10.1002/cne.23802] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Revised: 03/16/2015] [Accepted: 04/29/2015] [Indexed: 02/02/2023]
Abstract
Fossils of mammals and their extinct relatives among cynodonts give evidence of correlated transformations affecting olfaction as well as mastication, head movement, and ventilation, and suggest evolutionary coupling of these seemingly separate anatomical regions into a larger integrated system of ortho-retronasal olfaction. Evidence from paleontology and physiology suggests that ortho-retronasal olfaction played a critical role at three stages of mammalian cortical evolution: early mammalian brain development was driven in part by ortho-retronasal olfaction; the bauplan for neocortex had higher-level association functions derived from olfactory cortex; and human cortical evolution was enhanced by ortho-retronasal smell.
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Affiliation(s)
- Timothy B. Rowe
- Jackson School of Geosciences, The University of Texas at Austin, Austin, TX, 78712 USA
| | - Gordon M. Shepherd
- Department of Neurobiology, Yale University School of Medicine, New Haven, CT, 06510 USA
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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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20
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Ashwell KWS. Quantitative analysis of somatosensory cortex development in eutherians, with a comparison with metatherians and monotremes. Somatosens Mot Res 2015; 32:137-52. [DOI: 10.3109/08990220.2015.1004046] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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21
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Ashwell KWS. Quantitative analysis of somatosensory cortex development in metatherians and monotremes, with comparison to the laboratory rat. Somatosens Mot Res 2014; 32:87-98. [DOI: 10.3109/08990220.2014.978849] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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22
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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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23
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Green PA, Van Valkenburgh B, Pang B, Bird D, Rowe T, Curtis A. Respiratory and olfactory turbinal size in canid and arctoid carnivorans. J Anat 2012; 221:609-21. [PMID: 23035637 DOI: 10.1111/j.1469-7580.2012.01570.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/11/2012] [Indexed: 11/29/2022] Open
Abstract
Within the nasal cavity of mammals is a complex scaffold of paper-thin bones that function in respiration and olfaction. Known as turbinals, the bones greatly enlarge the surface area available for conditioning inspired air, reducing water loss, and improving olfaction. Given their functional significance, the relative development of turbinal bones might be expected to differ among species with distinct olfactory, thermoregulatory and/or water conservation requirements. Here we explore the surface area of olfactory and respiratory turbinals relative to latitude and diet in terrestrial Caniformia, a group that includes the canid and arctoid carnivorans (mustelids, ursids, procyonids, mephitids, ailurids). Using high-resolution computed tomography x-ray scans, we estimated respiratory and olfactory turbinal surface area and nasal chamber volume from three-dimensional virtual models of skulls. Across the Caniformia, respiratory surface area scaled isometrically with estimates of body size and there was no significant association with climate, as estimated by latitude. Nevertheless, one-on-one comparisons of sister taxa suggest that arctic species may have expanded respiratory turbinals. Olfactory surface area scaled isometrically among arctoids, but showed positive allometry in canids, reflecting the fact that larger canids, all of which are carnivorous, had relatively greater olfactory surface areas. In addition, among the arctoids, large carnivorous species such as the polar bear (Ursus maritimus) and wolverine (Gulo gulo) also displayed enlarged olfactory turbinals. More omnivorous caniform species that feed on substantial quantities of non-vertebrate foods had less expansive olfactory turbinals. Because large carnivorous species hunt widely dispersed prey, an expanded olfactory turbinal surface area may improve a carnivore's ability to detect prey over great distances using olfactory cues.
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Affiliation(s)
- Patrick A Green
- Department of Ecology and Evolutionary Biology, UCLA, Los Angeles, CA 90095-1606, USA
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Ashwell KWS, Hardman CD. Distinct development of the trigeminal sensory nuclei in platypus and echidna. BRAIN, BEHAVIOR AND EVOLUTION 2012; 79:261-74. [PMID: 22722086 DOI: 10.1159/000338079] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Accepted: 03/13/2012] [Indexed: 11/19/2022]
Abstract
Both lineages of the modern monotremes have been reported to be capable of electroreception using the trigeminal pathways and it has been argued that electroreception arose in an aquatic platypus-like ancestor of both modern monotreme groups. On the other hand, the trigeminal sensory nuclear complex of the platypus is highly modified for processing tactile and electrosensory information from the bill, whereas the trigeminal sensory nuclear complex of the short-beaked echidna (Tachyglossus aculeatus) is not particularly specialized. If the common ancestor for both platypus and echidna were an electroreceptively and trigeminally specialized aquatic feeder, one would expect the early stages of development of the trigeminal sensory nuclei in both species to show evidence of structural specialization from the outset. To determine whether this is the case, we examined the development of the trigeminal sensory nuclei in the platypus and short-beaked echidna using the Hill and Hubrecht embryological collections. We found that the highly specialized features of the platypus trigeminal sensory nuclei (i.e. the large size of the principal nucleus and oral part of the spinal trigeminal nuclear complex, and the presence of a dorsolateral parvicellular segment in the principal nucleus) appear around the time of hatching in the platypus, but are never seen at any stage in the echidna. Our findings support the proposition that the modern echidna and platypus are derived from a common ancestor with only minimal trigeminal specialization and that the peculiar anatomy of the trigeminal sensory nuclei in the modern platypus emerged in the ornithorhynchids after divergence from the tachyglossids.
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Affiliation(s)
- Ken W S Ashwell
- Department of Anatomy, School of Medical Sciences, University of New South Wales, Sydney, Australia.
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Macrini TE. Comparative Morphology of the Internal Nasal Skeleton of Adult Marsupials Based on X-ray Computed Tomography. BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY 2012. [DOI: 10.1206/365.1] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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26
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Kranioti EF, Holloway R, Senck S, Ciprut T, Grigorescu D, Harvati K. Virtual Assessment of the Endocranial Morphology of the Early Modern European Fossil Calvaria From Cioclovina, Romania. Anat Rec (Hoboken) 2011; 294:1083-92. [DOI: 10.1002/ar.21420] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2010] [Revised: 01/16/2011] [Accepted: 03/25/2011] [Indexed: 11/09/2022]
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27
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Olori JC. Digital Endocasts of the Cranial Cavity and Osseous Labyrinth of the Burrowing Snake Uropeltis woodmasoni (Alethinophidia: Uropeltidae). COPEIA 2010. [DOI: 10.1643/ch-09-082] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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28
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Abstract
Over two centuries after the first platypus specimen stirred the scientific community in Europe, the whole-genome sequence of the duck-billed platypus has been completed and is publicly available. After publication of eutherian and marsupial genomes, this is the first genome of a monotreme filling an important evolutionary gap between the divergence of birds more that 300 million years ago and marsupials more than 140 million years ago. Monotremes represent the most basal surviving branch of mammals and the platypus genome sequence allows unprecedented insights into the evolution of mammals and the fascinating biology of the egg-laying mammals. Here, we discuss some of the key findings of the analysis of the platypus genome and point to new findings and future research directions, which illustrate the broad impact of the platypus genome project for understanding monotreme biology and mammalian genome evolution.
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29
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Dong W. Virtual cranial endocast of the oldest giant panda (Ailuropoda microta) reveals great similarity to that of its extant relative. Naturwissenschaften 2008; 95:1079-83. [PMID: 18600311 DOI: 10.1007/s00114-008-0419-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2008] [Revised: 06/03/2008] [Accepted: 06/04/2008] [Indexed: 10/21/2022]
Abstract
Recent development of computed tomography and three-dimensional visualization techniques has enabled the non-destructive inspection of the endocast morphology of fossil neurocranium, the basic material for paleoneurological study. A virtual cranial endocast was reconstructed based on the first skull of the oldest giant panda, Ailuropoda microta, discovered recently and dated at more than 2 Myr (million years) ago. It was compared with that of the extant giant panda (A. melanoleuca) and that of the polar bear (Ursus maritimus), as well as CT slices of the late Pleistocene A. baconi. The overall endocast morphology of A. microta is more similar to that of A. baconi and A. melanoleuca than to that of U. maritimus. The absolute endocast size is the smallest in A. microta, largest in A. baconi, and intermediate in A. melanoleuca. However, the proportion of cerebral volume to total endocast size is very close to each other between the oldest and extant giant panda, as well as the sulcal length per unit area of cerebral endocast surface.
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Affiliation(s)
- Wei Dong
- Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, 100044, China.
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30
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Rowe T, Rich TH, Vickers-Rich P, Springer M, Woodburne MO. The oldest platypus and its bearing on divergence timing of the platypus and echidna clades. Proc Natl Acad Sci U S A 2008; 105:1238-42. [PMID: 18216270 PMCID: PMC2234122 DOI: 10.1073/pnas.0706385105] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2007] [Indexed: 11/18/2022] Open
Abstract
Monotremes have left a poor fossil record, and paleontology has been virtually mute during two decades of discussion about molecular clock estimates of the timing of divergence between the platypus and echidna clades. We describe evidence from high-resolution x-ray computed tomography indicating that Teinolophos, an Early Cretaceous fossil from Australia's Flat Rocks locality (121-112.5 Ma), lies within the crown clade Monotremata, as a basal platypus. Strict molecular clock estimates of the divergence between platypus and echidnas range from 17 to 80 Ma, but Teinolophos suggests that the two monotreme clades were already distinct in the Early Cretaceous, and that their divergence may predate even the oldest strict molecular estimates by at least 50%. We generated relaxed molecular clock models using three different data sets, but only one yielded a date overlapping with the age of Teinolophos. Morphology suggests that Teinolophos is a platypus in both phylogenetic and ecological aspects, and tends to contradict the popular view of rapid Cenozoic monotreme diversification. Whereas the monotreme fossil record is still sparse and open to interpretation, the new data are consistent with much slower ecological, morphological, and taxonomic diversification rates for monotremes than in their sister taxon, the therian mammals. This alternative view of a deep geological history for monotremes suggests that rate heterogeneities may have affected mammalian evolution in such a way as to defeat strict molecular clock models and to challenge even relaxed molecular clock models when applied to mammalian history at a deep temporal scale.
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Affiliation(s)
- Timothy Rowe
- *Jackson School of Geosciences, University of Texas, C1100, Austin, TX 78712
| | - Thomas H. Rich
- Museum Victoria, PO Box 666, Melbourne, Victoria 3001, Australia
- School of Geosciences, PO Box 28E, Monash University, Victoria 3800, Australia
| | | | - Mark Springer
- Department of Biology, University of California, Riverside, CA 92521; and
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GIANNINI NORBERTOP, SIMMONS NANCYB. The Chiropteran Premaxilla: A Reanalysis of Morphological Variation and Its Phylogenetic Interpretation. AMERICAN MUSEUM NOVITATES 2007. [DOI: 10.1206/0003-0082(2007)3585[1:tcparo]2.0.co;2] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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32
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Macrini TE, Rougier GW, Rowe T. Description of a Cranial Endocast from the Fossil MammalVincelestes neuquenianus (Theriiformes) and its Relevance to the Evolution of Endocranial Characters in Therians. Anat Rec (Hoboken) 2007; 290:875-92. [PMID: 17506058 DOI: 10.1002/ar.20551] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We generated a digital cranial endocast (infilling of the braincase) of Vincelestes neuquenianus, a Cretaceous theriiform mammal from Argentina, to achieve two goals. First, we described this endocast of Vincelestes to reconstruct the brain, associated soft-tissue structures, and internal osteological features. This report represents the first description of an endocast from a stem therian that is near crown group Theria (marsupials, placentals, and all descendants of that ancestor). Second, we examined 21 morphological characters related to the morphology of endocasts and endocranial osteology across 19 taxa (including Vincelestes) in the context of a current hypothesis about mammal phylogeny to identify potential synapomorphies for Theria. The digital endocast of Vincelestes is mostly complete, facilitating description in all views and allowing collection of accurate linear and volumetric measurements. However, it is unclear if the midbrain is exposed on the dorsal surface of the brain because of damage to this region of the endocast. Other portions of this specimen are extraordinarily well preserved, allowing identification of the accessory olfactory bulbs on the endocast, an ossified falx cerebri, and an osseous tentorium. The encephalization quotient (EQ) calculated for Vincelestes falls within the range of EQs of crown therians. Comparison of the endocranial characters across different mammalian taxa did not reveal any new synapomorphies for the clade Theria.
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Affiliation(s)
- Thomas E Macrini
- Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas, USA.
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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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