1
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Rawson JRG, Martinelli AG, Gill PG, Soares MB, Schultz CL, Rayfield EJ. Brazilian fossils reveal homoplasy in the oldest mammalian jaw joint. Nature 2024; 634:381-388. [PMID: 39322670 PMCID: PMC11464377 DOI: 10.1038/s41586-024-07971-3] [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: 12/08/2023] [Accepted: 08/20/2024] [Indexed: 09/27/2024]
Abstract
The acquisition of the load-bearing dentary-squamosal jaw joint was a key step in mammalian evolution1-5. Although this innovation has received decades of study, questions remain over when and how frequently a mammalian-like skull-jaw contact evolved, hindered by a paucity of three-dimensional data spanning the non-mammaliaform cynodont-mammaliaform transition. New discoveries of derived non-mammaliaform probainognathian cynodonts from South America have much to offer to this discussion. Here, to address this issue, we used micro-computed-tomography scanning to reconstruct the jaw joint anatomy of three key probainognathian cynodonts: Brasilodon quadrangularis, the sister taxon to Mammaliaformes6-8, the tritheledontid-related Riograndia guaibensis9 and the tritylodontid Oligokyphus major. We find homoplastic evolution in the jaw joint in the approach to mammaliaforms, with ictidosaurs (Riograndia plus tritheledontids) independently evolving a dentary-squamosal contact approximately 17 million years before this character first appears in mammaliaforms of the Late Triassic period10-12. Brasilodon, contrary to previous descriptions6-8, lacks an incipient dentary condyle and squamosal glenoid and the jaws articulate solely using a plesiomorphic quadrate-articular joint. We postulate that the jaw joint underwent marked evolutionary changes in probainognathian cynodonts. Some probainognathian clades independently acquired 'double' craniomandibular contacts, with mammaliaforms attaining a fully independent dentary-squamosal articulation with a conspicuous dentary condyle and squamosal glenoid in the Late Triassic. The dentary-squamosal contact, which is traditionally considered to be a typical mammalian feature, therefore evolved more than once and is more evolutionary labile than previously considered.
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Affiliation(s)
- James R G Rawson
- Palaeobiology Research Group, School of Earth Sciences, University of Bristol, Bristol, UK.
| | - Agustín G Martinelli
- Museo Argentino Ciencias Naturales "Bernardino Rivadavia"-CONICET, Buenos Aires, Argentina.
| | - Pamela G Gill
- Palaeobiology Research Group, School of Earth Sciences, University of Bristol, Bristol, UK
- Natural History Museum, London, UK
| | - Marina B Soares
- Museu Nacional, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Cesar L Schultz
- Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Emily J Rayfield
- Palaeobiology Research Group, School of Earth Sciences, University of Bristol, Bristol, UK.
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2
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Pommerening SDV, Martin T. Chewing shrews: Examining the morphology and function of the masticatory musculature in Soricidae via diffusible iodine-based contrast-enhanced computed tomography. J Morphol 2024; 285:e21761. [PMID: 39180211 DOI: 10.1002/jmor.21761] [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: 06/04/2024] [Revised: 07/26/2024] [Accepted: 08/02/2024] [Indexed: 08/26/2024]
Abstract
Essential for sustaining a high metabolic rate is the efficient fragmentation of food, which is determined by molar morphology and the movement of the jaw. The latter is related to the jaw morphology and the arrangement of the masticatory muscles. Soricid jaw apparatuses are unique among mammals, as the articulation facet on the condylar process is separated into a dorsal and a ventral part, which has often been linked to more differentiated jaw motions. Soricidae also possess a remarkably elongated angular process. However, the precise function of the unique morphology of soricid jaw apparatuses has not been fully understood yet. By digitally reconstructing the masticatory musculature via the diffusible iodine-based contrast-enhanced computed tomography technique, we show how the unique jaw morphology is reflected in the spatial organization as well as the inner architecture and respective fascicle orientations of the muscles. From the lines of action of the m. masseter and the m. pterygoideus internus, both muscles inserting on the lateral and medial side of the angular process, respectively, we infer that the angular process is substantial for roll and yaw rotations of the mandible. The m. masseter is subdivided into four and the m. pterygoideus internus into five subunits, each exhibiting a slightly different line of action and torque. This enables Soricidae to adjust and adapt these rotational movements according to the properties of the ingested food, allowing for more efficient fragmentation. Additionally, those guided rotational motions allow for precise occlusion despite tooth wear. The temporalis is the largest of the adductor muscles and is mainly responsible for exerting the bite force. Overall, the unique jaw bone morphology in conjunction with the complex muscle arrangement may contribute towards a more efficient energy gain and the maintenance of a high metabolic rate, which is crucial for small-bodied mammals such as shrews.
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Affiliation(s)
- Sebastian D V Pommerening
- Department of Paleontology, Institute of Organismic Biology, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
| | - Thomas Martin
- Department of Paleontology, Institute of Organismic Biology, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
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3
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Bishop PJ, Pierce SE. The fossil record of appendicular muscle evolution in Synapsida on the line to mammals: Part I-Forelimb. Anat Rec (Hoboken) 2024; 307:1764-1825. [PMID: 37726984 DOI: 10.1002/ar.25312] [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: 03/17/2023] [Revised: 07/15/2023] [Accepted: 08/08/2023] [Indexed: 09/21/2023]
Abstract
This paper is the first in a two-part series that charts the evolution of appendicular musculature along the mammalian stem lineage, drawing upon the exceptional fossil record of extinct synapsids. Here, attention is focused on muscles of the forelimb. Understanding forelimb muscular anatomy in extinct synapsids, and how this changed on the line to mammals, can provide important perspective for interpreting skeletal and functional evolution in this lineage, and how the diversity of forelimb functions in extant mammals arose. This study surveyed the osteological evidence for muscular attachments in extinct mammalian and nonmammalian synapsids, two extinct amniote outgroups, and a large selection of extant mammals, saurians, and salamanders. Observations were integrated into an explicit phylogenetic framework, comprising 73 character-state complexes covering all muscles crossing the shoulder, elbow, and wrist joints. These were coded for 33 operational taxonomic units spanning >330 Ma of tetrapod evolution, and ancestral state reconstruction was used to evaluate the sequence of muscular evolution along the stem lineage from Amniota to Theria. In addition to producing a comprehensive documentation of osteological evidence for muscle attachments in extinct synapsids, this work has clarified homology hypotheses across disparate taxa and helped resolve competing hypotheses of muscular anatomy in extinct species. The evolutionary history of mammalian forelimb musculature was a complex and nonlinear narrative, punctuated by multiple instances of convergence and concentrated phases of anatomical transformation. More broadly, this study highlights the great insight that a fossil-based perspective can provide for understanding the assembly of novel body plans.
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Affiliation(s)
- Peter J Bishop
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA
- Geosciences Program, Queensland Museum, Brisbane, Queensland, Australia
| | - Stephanie E Pierce
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA
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4
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Benoit J, Araujo R, Lund ES, Bolton A, Lafferty T, Macungo Z, Fernandez V. Early synapsids neurosensory diversity revealed by CT and synchrotron scanning. Anat Rec (Hoboken) 2024. [PMID: 38600433 DOI: 10.1002/ar.25445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Revised: 03/17/2024] [Accepted: 03/18/2024] [Indexed: 04/12/2024]
Abstract
Non-mammaliaform synapsids (NMS) represent the closest relatives of today's mammals among the early amniotes. Exploring their brain and nervous system is key to understanding how mammals evolved. Here, using CT and Synchrotron scanning, we document for the first time three extreme cases of neurosensory and behavioral adaptations that probe into the wide range of unexpected NMS paleoneurological diversity. First, we describe adaptations to low-frequency hearing and low-light conditions in the non-mammalian cynodont Cistecynodon parvus, supporting adaptations to an obligatory fossorial lifestyle. Second, we describe the uniquely complex and three-dimensional maxillary canal morphology of the biarmosuchian Pachydectes elsi, which suggests that it may have used its cranial bosses for display or low-energy combat. Finally, we introduce a paleopathology found in the skull of Moschognathus whaitsi. Since the specimen was not fully grown, this condition suggests the possibility that this species might have engaged in playful fighting as juveniles-a behavior that is both social and structured. Additionally, this paper discusses other evidence that could indicate that tapinocephalid dinocephalians were social animals, living and interacting closely with one another. Altogether, these examples evidence the wide range of diversity of neurological structures and complex behavior in NMS.
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Affiliation(s)
- J Benoit
- Evolutionary Studies Institute and School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
| | - R Araujo
- Instituto de Plasmas e Fusão Nuclear, InstitutoSuperior Técnico, Universidade de Lisboa, Lisboa, Portugal
| | - E S Lund
- Evolutionary Studies Institute and School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
| | - A Bolton
- Evolutionary Studies Institute and School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
| | - T Lafferty
- Evolutionary Studies Institute and School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Z Macungo
- Evolutionary Studies Institute and School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
| | - V Fernandez
- European Synchrotron Radiation Facility, Grenoble, France
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5
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She Y, Ren R, Jiang N. Mechanical stress can regulate temporomandibular joint cavitation via signalling pathways. Dev Biol 2024; 507:1-8. [PMID: 38114053 DOI: 10.1016/j.ydbio.2023.12.006] [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: 05/04/2023] [Revised: 12/10/2023] [Accepted: 12/15/2023] [Indexed: 12/21/2023]
Abstract
The temporomandibular joint (TMJ), composed of temporal fossa, mandibular condyle and a fibrocartilage disc with upper and lower cavities, is the biggest synovial joint and biomechanical hinge of the craniomaxillofacial musculoskeletal system. The initial events that give rise to TMJ cavities across diverse species are not fully understood. Most studies focus on the pivotal role of molecules such as Indian hedgehog (Ihh) and hyaluronic acid (HA) in TMJ cavitation. Although biologists have observed that mechanical stress plays an irreplaceable role in the development of biological tissues and organs, few studies have been concerned with how mechanical stress regulates TMJ cavitation. Based on the evidence from human or other animal embryos today, it is implicated that mechanical stress plays an essential role in TMJ cavitation. In this review, we discuss the relationship between mechanical stress and TMJ cavitation from evo-devo perspectives and review the clinical features and potential pathogenesis of TMJ dysplasia.
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Affiliation(s)
- Yilin She
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Disease and West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Rong Ren
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Disease and West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Nan Jiang
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Disease and West China Hospital of Stomatology, Sichuan University, Chengdu, China.
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6
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Wang H, Wang Y. Middle ear innovation in Early Cretaceous eutherian mammals. Nat Commun 2023; 14:6831. [PMID: 37884521 PMCID: PMC10603157 DOI: 10.1038/s41467-023-42606-7] [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: 03/07/2022] [Accepted: 10/16/2023] [Indexed: 10/28/2023] Open
Abstract
The middle ear ossicles in modern mammals are repurposed from postdentary bones in non-mammalian cynodonts. Recent discoveries by palaeontological and embryonic studies have developed different models for the middle ear evolution in mammaliaforms. However, little is known about the evolutionary scenario of the middle ear in early therians. Here we report a detached middle ear preserved in a new eutherian mammal from the Early Cretaceous Jehol Biota. The well-preserved articulation of the malleus and incus suggest that the saddle-shaped incudomallear joint is a major apomorphy of Early Cretaceous eutherians. By contrast to the distinct saddle-like incudomallear articulation in therians, differences between the overlapping versus the half-overlapping incudomallear joints in monotremes and stem mammals would be relatively minor. The middle ear belongs to the microtype by definition, indicating its adaptation to high-frequency hearing. Current evidence indicates that significant evolutionary innovations of the middle ear in modern therians evolved in Early Cretaceous.
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Affiliation(s)
- Haibing Wang
- Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, 100044, Beijing, China.
| | - Yuanqing Wang
- Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, 100044, Beijing, China.
- College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, 100049, Beijing, China.
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7
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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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8
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Hall BK, Hanken J. Modularity, homology, heterochrony: Gavin de Beer's legacy to the mammalian skull. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220078. [PMID: 37183898 PMCID: PMC10184244 DOI: 10.1098/rstb.2022.0078] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023] Open
Abstract
Modularity (segmentation), homology and heterochrony were essential concepts embraced by Gavin de Beer in his studies of the development and evolution of the vertebrate skull. While his pioneering contributions have stood the test of time, our understanding of the biological processes that underlie each concept has evolved. We assess de Beer's initial training as an experimental embryologist; his switch to comparative and descriptive studies of skulls, jaws and middle ear ossicles; and his later research on the mammalian skull, including his approach to head segmentation. The role of cells of neural crest and mesodermal origin in skull development, and developmental, palaeontological and molecular evidence for the origin of middle ear ossicles in the evolutionary transition from reptiles to mammals are used to illustrate our current understanding of modularity, homology and heterochrony. This article is part of the theme issue 'The mammalian skull: development, structure and function'.
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Affiliation(s)
- Brian K Hall
- Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4J1
| | - James Hanken
- Museum of Comparative Zoology, Harvard University, Cambridge, MA 02138, USA
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9
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Harano T, Asahara M. Revisiting the evolutionary trend toward the mammalian lower jaw in non-mammalian synapsids in a phylogenetic context. PeerJ 2023; 11:e15575. [PMID: 37361048 PMCID: PMC10289081 DOI: 10.7717/peerj.15575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 05/25/2023] [Indexed: 06/28/2023] Open
Abstract
The mammalian lower jaw comprises a single bone, the dentary, which is a unique feature among vertebrates. The lower jaws of extinct non-mammalian synapsids were composed of the dentary and several postdentary bones. Synapsid fossils exhibit variation in the dentary size relative to the overall lower jaw. An evolutionary trend toward dentary enlargement and postdentary reduction in non-mammalian synapsids has long been documented but has not been established using modern phylogenetic comparative methods. In this study, we examine the evolutionary pattern of dentary size relative to the lower jaw through phylogenetic analyses of measurements in a broad range of non-mammalian synapsid taxa. Our analyses revealed an evolutionary trend toward dentary area enlargement relative to the overall lower jaw in the lateral view across all non-mammalian synapsids. This trend is likely due to vertical expansion of the dentary given that the same trend is not evident when looking at anterior to posterior measurements of the dentary relative to the lower jaw as a whole in lateral view. Ancestral character reconstructions revealed that the evolution of the measurements was not unidirectional in non-mammalian synapsids. Our results provide no evidence of an evolutionary trend toward the dentary enlargement at the expense of postdentary bones across non-mammalian synapsids. This implies that the evolutionary origin of the mammalian lower jaw is not adequately explained by the evolutionary trend of dentary enlargement throughout non-mammalian synapsids. Instead, selection that occurred during the transition from non-mammalian cynodonts to early mammals may have produced the mammalian lower jaw.
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Affiliation(s)
- Tomohiro Harano
- Division of Liberal Arts and Sciences, Aichi Gakuin University, Nisshin, Aichi, Japan
| | - Masakazu Asahara
- Division of Liberal Arts and Sciences, Aichi Gakuin University, Nisshin, Aichi, Japan
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10
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Capshaw G, Brown AD, Peña JL, Carr CE, Christensen-Dalsgaard J, Tollin DJ, Womack MC, McCullagh EA. The continued importance of comparative auditory research to modern scientific discovery. Hear Res 2023; 433:108766. [PMID: 37084504 PMCID: PMC10321136 DOI: 10.1016/j.heares.2023.108766] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 03/23/2023] [Accepted: 04/05/2023] [Indexed: 04/23/2023]
Abstract
A rich history of comparative research in the auditory field has afforded a synthetic view of sound information processing by ears and brains. Some organisms have proven to be powerful models for human hearing due to fundamental similarities (e.g., well-matched hearing ranges), while others feature intriguing differences (e.g., atympanic ears) that invite further study. Work across diverse "non-traditional" organisms, from small mammals to avians to amphibians and beyond, continues to propel auditory science forward, netting a variety of biomedical and technological advances along the way. In this brief review, limited primarily to tetrapod vertebrates, we discuss the continued importance of comparative studies in hearing research from the periphery to central nervous system with a focus on outstanding questions such as mechanisms for sound capture, peripheral and central processing of directional/spatial information, and non-canonical auditory processing, including efferent and hormonal effects.
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Affiliation(s)
- Grace Capshaw
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD 21218, USA.
| | - Andrew D Brown
- Department of Speech and Hearing Sciences, University of Washington, Seattle, WA 98105, USA
| | - José L Peña
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Catherine E Carr
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | | | - Daniel J Tollin
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; Department of Otolaryngology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Molly C Womack
- Department of Biology, Utah State University, Logan, UT 84322, USA.
| | - Elizabeth A McCullagh
- Department of Integrative Biology, Oklahoma State University, Stillwater, OK 74078, USA.
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11
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Lautenschlager S, Fagan MJ, Luo ZX, Bird CM, Gill P, Rayfield EJ. Functional reorganisation of the cranial skeleton during the cynodont-mammaliaform transition. Commun Biol 2023; 6:367. [PMID: 37046052 PMCID: PMC10097706 DOI: 10.1038/s42003-023-04742-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Accepted: 03/21/2023] [Indexed: 04/14/2023] Open
Abstract
Skeletal simplification occurred in multiple vertebrate clades over the last 500 million years, including the evolution from premammalian cynodonts to mammals. This transition is characterised by the loss and reduction of cranial bones, the emergence of a novel jaw joint, and the rearrangement of the jaw musculature. These modifications have long been hypothesised to increase skull strength and efficiency during feeding. Here, we combine digital reconstruction and biomechanical modelling to show that there is no evidence for an increase in cranial strength and biomechanical performance. Our analyses demonstrate the selective functional reorganisation of the cranial skeleton, leading to reduced stresses in the braincase and the skull roof but increased stresses in the zygomatic region through this transition. This cranial functional reorganisation, reduction in mechanical advantage, and overall miniaturisation in body size are linked with a dietary specialisation to insectivory, permitting the subsequent morphological and ecological diversification of the mammalian lineage.
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Affiliation(s)
- Stephan Lautenschlager
- School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UK.
| | | | - Zhe-Xi Luo
- Department of Organismal Biology and Anatomy, University of Chicago, Chicago, USA
| | - Charlotte M Bird
- School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UK
| | - Pamela Gill
- Earth Sciences Department, The Natural History Museum, London, UK
- Bristol Palaeobiology Group, School of Earth Sciences, University of Bristol, Bristol, UK
| | - Emily J Rayfield
- Bristol Palaeobiology Group, School of Earth Sciences, University of Bristol, Bristol, UK.
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12
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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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13
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First monotreme from the Late Cretaceous of South America. Commun Biol 2023; 6:146. [PMID: 36797304 PMCID: PMC9935847 DOI: 10.1038/s42003-023-04498-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Accepted: 01/18/2023] [Indexed: 02/18/2023] Open
Abstract
Monotremata is a clade of egg-lying mammals, represented by the living platypus and echidnas, which is endemic to Australia, and adjacent islands. Occurrence of basal monotremes in the Early Cretaceous of Australia has led to the consensus that this clade originated on that continent, arriving later to South America. Here we report on the discovery of a Late Cretaceous monotreme from southern Argentina, demonstrating that monotremes were present in circumpolar regions by the end of the Mesozoic, and that their distinctive anatomical features were probably present in these ancient forms as well.
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14
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Anthwal N, Tucker AS. Evolution and development of the mammalian jaw joint: Making a novel structure. Evol Dev 2023; 25:3-14. [PMID: 36504442 PMCID: PMC10078425 DOI: 10.1111/ede.12426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Revised: 11/08/2022] [Accepted: 11/22/2022] [Indexed: 12/14/2022]
Abstract
A jaw joint between the squamosal and dentary is a defining feature of mammals and is referred to as the temporomandibular joint (TMJ) in humans. Driven by changes in dentition and jaw musculature, this new joint evolved early in the mammalian ancestral lineage and permitted the transference of the ancestral jaw joint into the middle ear. The fossil record demonstrates the steps in the cynodont lineage that led to the acquisition of the TMJ, including the expansion of the dentary bone, formation of the coronoid process, and initial contact between the dentary and squamosal. From a developmental perspective, the components of the TMJ form through tissue interactions of muscle and skeletal elements, as well as through interaction between the jaw and the cranial base, with the signals involved in these interactions being both biomechanical and biochemical. In this review, we discuss the development of the TMJ in an evolutionary context. We describe the evolution of the TMJ in the fossil record and the development of the TMJ in embryonic development. We address the formation of key elements of the TMJ and how knowledge from developmental biology can inform our understanding of TMJ evolution.
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Affiliation(s)
- Neal Anthwal
- Centre for Craniofacial and Regenerative Biology, Faculty of Dentisry, Oral and Craniofacial Sciences, London, UK
| | - Abigail S Tucker
- Centre for Craniofacial and Regenerative Biology, Faculty of Dentisry, Oral and Craniofacial Sciences, London, UK
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15
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Schlosser G. Rebuilding ships while at sea-Character individuality, homology, and evolutionary innovation. J Morphol 2023; 284:e21522. [PMID: 36282954 PMCID: PMC10100095 DOI: 10.1002/jmor.21522] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 09/15/2022] [Accepted: 10/15/2022] [Indexed: 11/05/2022]
Abstract
How novel traits originate in evolution is still one of the most perplexing questions in Evolutionary Biology. Building on a previous account of evolutionary innovation, I here propose that evolutionary novelties are those individualized characters that are not homologous to any characters in the ancestor. To clarify this definition, I here provide a detailed analysis of the concepts of "character individuality" and "homology" first, before addressing their role for our understanding of evolutionary innovation. I will argue (1) that functional as well as structural considerations are important for character individualization; and (2) that compositional (structural) and positional homology need to be clearly distinguished to properly describe the evolutionary transformations of hierarchically structured characters. My account will therefore integrate functional and structural perspectives and put forward a new multi-level view of character identity and transformation.
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Affiliation(s)
- Gerhard Schlosser
- School of Biological and Chemical Sciences, University of Galway, Galway, Ireland
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16
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Harano T, Asahara M. The anteriorization of tooth position underlies the atavism of tooth morphology: Insights into the morphogenesis of mammalian molars. Evolution 2022; 76:2986-3000. [PMID: 36200621 DOI: 10.1111/evo.14637] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 08/29/2022] [Accepted: 09/15/2022] [Indexed: 01/22/2023]
Abstract
The evolution and development of complex molars as a key innovation in mammals have long been of interest yet remain poorly understood. With reference to century-old theories and modern findings, we focused on the teeth of pinnipeds (Carnivora) and cetaceans (Cetartiodactyla), which are morphologically simple compared with those of other mammals, and thus can be considered a reversal toward the ancestral state of nonmammalian synapsids. By reconstructing the evolutionary history of tooth complexity for the phylogenies of Carnivora and Cetartiodactyla, we established that a secondary evolution of simple teeth from more complex molars has occurred independently multiple times. Our phylogenetic comparative analyses showed that a simplification in tooth morphology was correlated with a more anterior dentition position relative to the component bones of the upper jaw in both Carnivora and Cetartiodactyla. These results suggest that the anterior shift of tooth position relative to the morphogenetic fields present in the jaw contributed to the evolutionary simplification in molar morphology. Our findings provide insights into the developmental basis of complex mammalian dentition.
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Affiliation(s)
- Tomohiro Harano
- Division of Liberal Arts and Sciences, Aichi Gakuin University, Nisshin, 470-0195, Japan
| | - Masakazu Asahara
- Division of Liberal Arts and Sciences, Aichi Gakuin University, Nisshin, 470-0195, Japan
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17
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Heffner RS, Koay G, Heffner HE, Mason MJ. Hearing in African pygmy hedgehogs (Atelerix albiventris): audiogram, sound localization, and ear anatomy. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2022; 208:653-670. [PMID: 36282301 DOI: 10.1007/s00359-022-01579-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 08/21/2022] [Accepted: 09/24/2022] [Indexed: 12/14/2022]
Abstract
The behavioral audiogram and sound localization performance, together with the middle and inner ear anatomy, were examined in African pygmy hedgehogs Atelerix albiventris. Their auditory sensitivity at 60 dB SPL extended from 2 to 46 kHz, revealing a relatively narrow hearing range of 4.6 octaves, with a best sensitivity of 21 dB at 8 kHz. Their noise-localization acuity around the midline (minimum audible angle) was 14°, matching the mean of terrestrial mammals. The African pygmy hedgehog was not able to localize low-frequency pure tones or a 3-kHz amplitude-modulated tone when forced to rely on the interaural phase-difference cue, a trait shared by at least nine other mammals. The middle ear of Atelerix has a configuration including an ectotympanic which is not fused to the surrounding bones, a substantial pars flaccida, a synostosed malleo-ectotympanic articulation and a 'microtype' malleus. The hearing and sound localization of A. albiventris is compared to that of a broad range of other mammals. It is shown that a malleus morphology like that of Atelerix, including a stiff articulation with the ectotympanic, is a consistent feature of other mammals that do not hear frequencies below 400 Hz.
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Affiliation(s)
- Rickye S Heffner
- Department of Psychology, University of Toledo, Toledo, OH, 43606, USA.
| | - Gimseong Koay
- Department of Psychology, University of Toledo, Toledo, OH, 43606, USA
| | - Henry E Heffner
- Department of Psychology, University of Toledo, Toledo, OH, 43606, USA
| | - Matthew J Mason
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, CB2 3EG, UK
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18
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Schwab JA, Young MT, Walsh SA, Witmer LM, Herrera Y, Brochu CA, Butler IB, Brusatte SL. Ontogenetic variation in the crocodylian vestibular system. J Anat 2022; 240:821-832. [PMID: 34841534 PMCID: PMC9005688 DOI: 10.1111/joa.13601] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 10/29/2021] [Accepted: 11/19/2021] [Indexed: 01/20/2023] Open
Abstract
Crocodylians today live in tropical to subtropical environments, occupying mostly shallow waters. Their body size changes drastically during ontogeny, as do their skull dimensions and bite forces, which are associated with changes in prey preferences. Endocranial neurosensory structures have also shown to change ontogenetically, but less is known about the vestibular system of the inner ear. Here we use 30 high-resolution computed tomography (CT) scans and three-dimensional geometric morphometrics to investigate the size and shape changes of crocodylian endosseous labyrinths throughout ontogeny, across four stages (hatchling, juvenile, subadult and adult). We find two major patterns of ontogenetic change. First, the labyrinth increases in size during ontogeny, with negative allometry in relation to skull size. Second, labyrinth shape changes significantly, with hatchlings having shorter semicircular canal radii, with thicker diameters and an overall dorsoventrally shorter labyrinth than those of more mature individuals. We argue that the modification of the labyrinth during crocodylian ontogeny is related to constraints imposed by skull growth, due to fundamental changes in the crocodylian braincase during ontogeny (e.g. verticalisation of the basicranium), rather than changes in locomotion, diet, or other biological functions or behaviours.
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Affiliation(s)
- Julia A. Schwab
- School of GeoSciencesGrant InstituteUniversity of EdinburghEdinburghUK
| | - Mark T. Young
- School of GeoSciencesGrant InstituteUniversity of EdinburghEdinburghUK
| | - Stig A. Walsh
- School of GeoSciencesGrant InstituteUniversity of EdinburghEdinburghUK
- National Museum of ScotlandEdinburghUK
| | - Lawrence M. Witmer
- Department of Biomedical SciencesHeritage College of Osteopathic MedicineOhio Center for Ecology and Evolutionary StudiesOhio UniversityAthensOhioUSA
| | - Yanina Herrera
- CONICET. División Paleontología VertebradosMuseo de La Plata, FCNyMUNLPLa PlataArgentina
| | | | - Ian B. Butler
- School of GeoSciencesGrant InstituteUniversity of EdinburghEdinburghUK
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19
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Bazzana KD, Evans DC, Bevitt JJ, Reisz RR. Neurosensory anatomy of Varanopidae and its implications for early synapsid evolution. J Anat 2022; 240:833-849. [PMID: 34775594 PMCID: PMC9005680 DOI: 10.1111/joa.13593] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 11/04/2021] [Accepted: 11/04/2021] [Indexed: 12/11/2022] Open
Abstract
Varanopids are a group of Palaeozoic terrestrial amniotes which represent one of the earliest-diverging groups of synapsids, but their palaeoneurology has gone largely unstudied and recent analyses have challenged their traditional placement within synapsids. We utilized computed tomography (CT) to study the virtual cranial and otic endocasts of six varanopids, including representative taxa of both mycterosaurines and varanodontines. Our results show that the varanopid brain is largely plesiomorphic, being tubular in shape and showing no expansion of the cerebrum or olfactory bulbs, but is distinct in showing highly expanded floccular fossae. The housing of the varanopid bony labyrinth is also distinct, in that the labyrinth is bounded almost entirely by the supraoccipital-opisthotic complex, with the prootic only bordering the ventral portion of the vestibule. The bony labyrinth is surprisingly well-ossified, clearly preserving the elliptical, sub-orthogonal canals, prominent ampullae, and the short, undifferentiated vestibule; this high degree of ossification is similar to that seen in therapsid synapsids and supports the traditional placement of varanopids within Synapsida. The enlarged anterior canal, together with the elliptical, orthogonal canals and enlarged floccular fossa, lend support for the fast head movements indicated by the inferred predatory feeding mode of varanopids. Reconstructed neurosensory anatomy indicates that varanopids may have a much lower-frequency hearing range compared to more derived synapsids, suggesting that, despite gaining some active predatory features, varanopids retain plesiomorphic hearing capabilities. As a whole, our data reveal that the neuroanatomy of pelycosaur-grade synapsids is far more complex than previously anticipated.
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Affiliation(s)
- Kayla D. Bazzana
- Department of BiologyUniversity of Toronto MississaugaMississaugaCanada
- Department of Natural HistoryRoyal Ontario MuseumTorontoCanada
| | - David C. Evans
- Department of Natural HistoryRoyal Ontario MuseumTorontoCanada
- Department of Ecology and Evolutionary BiologyUniversity of TorontoTorontoCanada
| | - Joseph J. Bevitt
- Australian Centre for Neutron ScatteringAustralian Nuclear Science and Technology OrganisationLucas HeightsNew South WhalesAustralia
| | - Robert R. Reisz
- Department of BiologyUniversity of Toronto MississaugaMississaugaCanada
- International Center of Future ScienceDinosaur Evolution Research CenterJilin UniversityChangchunJilin ProvinceChina
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20
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Wible JR, Shelley SL, Bi S. Response to 'Monotreme middle ear is not primitive for Mammalia'. Natl Sci Rev 2021; 8:nwab132. [PMID: 34858617 PMCID: PMC8566169 DOI: 10.1093/nsr/nwab132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 07/12/2021] [Accepted: 07/21/2021] [Indexed: 11/15/2022] Open
Affiliation(s)
- John R Wible
- Section of Mammals, Carnegie Museum of Natural History, USA
- Centre for Vertebrate Evolutionary Biology, Yunnan University, China
| | - Sarah L Shelley
- Section of Mammals, Carnegie Museum of Natural History, USA
- School of Geosciences, University of Edinburgh, UK
| | - Shundong Bi
- Section of Mammals, Carnegie Museum of Natural History, USA
- Centre for Vertebrate Evolutionary Biology, Yunnan University, China
- Department of Biology, Indiana University of Pennsylvania, USA
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21
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Waldmann L, Leyhr J, Zhang H, Öhman-Mägi C, Allalou A, Haitina T. The broad role of Nkx3.2 in the development of the zebrafish axial skeleton. PLoS One 2021; 16:e0255953. [PMID: 34411150 PMCID: PMC8376051 DOI: 10.1371/journal.pone.0255953] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 07/27/2021] [Indexed: 11/18/2022] Open
Abstract
The transcription factor Nkx3.2 (Bapx1) is an important chondrocyte maturation inhibitor. Previous Nkx3.2 knockdown and overexpression studies in non-mammalian gnathostomes have focused on its role in primary jaw joint development, while the function of this gene in broader skeletal development is not fully described. We generated a mutant allele of nkx3.2 in zebrafish with CRISPR/Cas9 and applied a range of techniques to characterize skeletal phenotypes at developmental stages from larva to adult, revealing loss of the jaw joint, fusions in bones of the occiput, morphological changes in the Weberian apparatus, and the loss or deformation of bony elements derived from basiventral cartilages of the vertebrae. Axial phenotypes are reminiscent of Nkx3.2 knockout in mammals, suggesting that the function of this gene in axial skeletal development is ancestral to osteichthyans. Our results highlight the broad role of nkx3.2 in zebrafish skeletal development and its context-specific functions in different skeletal elements.
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Affiliation(s)
- Laura Waldmann
- Department of Organismal Biology, Uppsala University, Uppsala, Sweden
| | - Jake Leyhr
- Department of Organismal Biology, Uppsala University, Uppsala, Sweden
| | - Hanqing Zhang
- Division of Visual Information and Interaction, Department of Information Technology, Uppsala University, Uppsala, Sweden
- Science for Life Laboratory BioImage Informatics Facility, Uppsala, Sweden
| | - Caroline Öhman-Mägi
- Department of Materials Science and Engineering, Uppsala University, Uppsala, Sweden
| | - Amin Allalou
- Division of Visual Information and Interaction, Department of Information Technology, Uppsala University, Uppsala, Sweden
- Science for Life Laboratory BioImage Informatics Facility, Uppsala, Sweden
| | - Tatjana Haitina
- Department of Organismal Biology, Uppsala University, Uppsala, Sweden
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22
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Grossnickle DM, Weaver LN, Jäger KRK, Schultz JA. The evolution of anteriorly directed molar occlusion in mammals. Zool J Linn Soc 2021. [DOI: 10.1093/zoolinnean/zlab039] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Abstract
In non-mammalian synapsids and early mammals, evolutionary transformations in the feeding and hearing apparatuses are posited to have been prerequisites for the radiation of extant mammals. Unlike most vertebrates, including many early synapsids, mammals have precise dental occlusion, a lower jaw composed of one bone, and middle ear ossicles derived from ancestral jaw bones. We illuminate a related functional transition: therian mammals (eutherians and metatherians) evolved anteriorly directed chewing strokes, which are absent in other synapsid lineages. Anteriorly directed jaw movement during occlusion necessitates anteriorly directed muscle force vectors, and we posit that a shift in muscle orientation is reflected in the fossil record by the evolutionary appearance of a posteriorly positioned angular process in cladotherians (therians and their close kin). Anteriorly directed occlusion might have been absent in earlier synapsids because of the presence of attached middle ear elements in the posterior region of the jaw that prohibited the posterior insertion of jaw musculature. These changes to the masticatory apparatus in cladotherians are likely to have permitted the evolution of novel masticatory movements, including grinding in both the anterior and medial directions (e.g. rodents and ungulates, respectively). Thus, this evolutionary transition might have been a crucial prerequisite for the dietary diversification of therians.
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Affiliation(s)
- David M Grossnickle
- Department of Biology, Life Sciences Building, University of Washington, Seattle, WA, USA
| | - Lucas N Weaver
- Department of Biology, Life Sciences Building, University of Washington, Seattle, WA, USA
| | - Kai R K Jäger
- Section Palaeontology, Institute of Geosciences, Rheinische Friedrich-Wilhelms-Universität Bonn, Nussallee 8, Bonn, Germany
| | - Julia A Schultz
- Section Palaeontology, Institute of Geosciences, Rheinische Friedrich-Wilhelms-Universität Bonn, Nussallee 8, Bonn, Germany
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23
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Morales-García NM, Gill PG, Janis CM, Rayfield EJ. Jaw shape and mechanical advantage are indicative of diet in Mesozoic mammals. Commun Biol 2021; 4:242. [PMID: 33623117 PMCID: PMC7902851 DOI: 10.1038/s42003-021-01757-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Accepted: 01/14/2021] [Indexed: 01/31/2023] Open
Abstract
Jaw morphology is closely linked to both diet and biomechanical performance, and jaws are one of the most common Mesozoic mammal fossil elements. Knowledge of the dietary and functional diversity of early mammals informs on the ecological structure of palaeocommunities throughout the longest era of mammalian evolution: the Mesozoic. Here, we analyse how jaw shape and mechanical advantage of the masseter (MAM) and temporalis (MAT) muscles relate to diet in 70 extant and 45 extinct mammals spanning the Late Triassic-Late Cretaceous. In extant mammals, jaw shape discriminates well between dietary groups: insectivores have long jaws, carnivores intermediate to short jaws, and herbivores have short jaws. Insectivores have low MAM and MAT, carnivores have low MAM and high MAT, and herbivores have high MAM and MAT. These traits are also informative of diet among Mesozoic mammals (based on previous independent determinations of diet) and set the basis for future ecomorphological studies.
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Affiliation(s)
| | - Pamela G Gill
- School of Earth Sciences, Wills Memorial Building, University of Bristol, Bristol, UK
- Department of Earth Sciences, Natural History Museum, London, UK
| | - Christine M Janis
- School of Earth Sciences, Wills Memorial Building, University of Bristol, Bristol, UK
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI, USA
| | - Emily J Rayfield
- School of Earth Sciences, Wills Memorial Building, University of Bristol, Bristol, UK
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24
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Wang J, Wible JR, Guo B, Shelley SL, Hu H, Bi S. A monotreme-like auditory apparatus in a Middle Jurassic haramiyidan. Nature 2021; 590:279-283. [PMID: 33505017 DOI: 10.1038/s41586-020-03137-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Accepted: 12/10/2020] [Indexed: 01/30/2023]
Abstract
Among extant vertebrates, mammals are distinguished by having a chain of three auditory ossicles (the malleus, incus and stapes) that transduce sound waves and promote an increased range of audible-especially high-frequencies1. By contrast, the homologous bones in early fossil mammals and relatives also functioned in chewing through their bony attachments to the lower jaw2. Recent discoveries of well-preserved Mesozoic mammals have provided glimpses into the transition from the dual (masticatory and auditory) to the single auditory function for the ossicles, which is now widely accepted to have occurred at least three times in mammal evolution3-6. Here we report a skull and postcranium that we refer to the haramiyidan Vilevolodon diplomylos (dating to the Middle Jurassic epoch (160 million years ago)) and that shows excellent preservation of the malleus, incus and ectotympanic (which supports the tympanic membrane). After comparing this fossil with other Mesozoic and extant mammals, we propose that the overlapping incudomallear articulation found in this and other Mesozoic fossils, in extant monotremes and in early ontogeny in extant marsupials and placentals is a morphology that evolved in several groups of mammals in the transition from the dual to the single function for the ossicles.
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Affiliation(s)
- Junyou Wang
- Centre for Vertebrate Evolutionary Biology, Institute of Palaeontology, Yunnan University, Kunming, China.,Inner Mongolia Museum of Natural History, Hohhot, China
| | - John R Wible
- Centre for Vertebrate Evolutionary Biology, Institute of Palaeontology, Yunnan University, Kunming, China. .,Section of Mammals, Carnegie Museum of Natural History, Pittsburgh, PA, USA.
| | - Bin Guo
- Inner Mongolia Museum of Natural History, Hohhot, China
| | - Sarah L Shelley
- Section of Mammals, Carnegie Museum of Natural History, Pittsburgh, PA, USA.,School of Geosciences, University of Edinburgh, Edinburgh, UK
| | - Han Hu
- Zoology Division, School of Environmental and Rural Sciences, University of New England, Armidale, New South Wales, Australia
| | - Shundong Bi
- Centre for Vertebrate Evolutionary Biology, Institute of Palaeontology, Yunnan University, Kunming, China. .,Department of Biology, Indiana University of Pennsylvania, Indiana, PA, USA.
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25
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Svandova E, Anthwal N, Tucker AS, Matalova E. Diverse Fate of an Enigmatic Structure: 200 Years of Meckel's Cartilage. Front Cell Dev Biol 2020; 8:821. [PMID: 32984323 PMCID: PMC7484903 DOI: 10.3389/fcell.2020.00821] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 08/03/2020] [Indexed: 12/16/2022] Open
Abstract
Meckel's cartilage was first described by the German anatomist Johann Friedrich Meckel the Younger in 1820 from his analysis of human embryos. Two hundred years after its discovery this paper follows the development and largely transient nature of the mammalian Meckel's cartilage, and its role in jaw development. Meckel's cartilage acts as a jaw support during early development, and a template for the later forming jaw bones. In mammals, its anterior domain links the two arms of the dentary together at the symphysis while the posterior domain ossifies to form two of the three ear ossicles of the middle ear. In between, Meckel's cartilage transforms to a ligament or disappears, subsumed by the growing dentary bone. Several human syndromes have been linked, directly or indirectly, to abnormal Meckel's cartilage formation. Herein, the evolution, development and fate of the cartilage and its impact on jaw development is mapped. The review focuses on developmental and cellular processes that shed light on the mechanisms behind the different fates of this cartilage, examining the control of Meckel's cartilage patterning, initiation and maturation. Importantly, human disorders and mouse models with disrupted Meckel's cartilage development are highlighted, in order to understand how changes in this cartilage impact on later development of the dentary and the craniofacial complex as a whole. Finally, the relative roles of tissue interactions, apoptosis, autophagy, macrophages and clast cells in the removal process are discussed. Meckel's cartilage is a unique and enigmatic structure, the development and function of which is starting to be understood but many interesting questions still remain.
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Affiliation(s)
- Eva Svandova
- Institute of Animal Physiology and Genetics, Academy of Sciences, Brno, Czechia
| | - Neal Anthwal
- Centre for Craniofacial and Regenerative Biology, King’s College London, Guy’s Hospital, London, United Kingdom
| | - Abigail S. Tucker
- Centre for Craniofacial and Regenerative Biology, King’s College London, Guy’s Hospital, London, United Kingdom
| | - Eva Matalova
- Institute of Animal Physiology and Genetics, Academy of Sciences, Brno, Czechia
- Department of Physiology, University of Veterinary and Pharmaceutical Sciences, Brno, Czechia
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26
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Celik MA, Phillips MJ. Conflict Resolution for Mesozoic Mammals: Reconciling Phylogenetic Incongruence Among Anatomical Regions. Front Genet 2020; 11:0651. [PMID: 32774343 PMCID: PMC7381353 DOI: 10.3389/fgene.2020.00651] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2019] [Accepted: 05/28/2020] [Indexed: 11/13/2022] Open
Abstract
The evolutionary history of Mesozoic mammaliaformes is well studied. Although the backbone of their phylogeny is well resolved, the placement of ecologically specialized groups has remained uncertain. Functional and developmental covariation has long been identified as an important source of phylogenetic error, yet combining incongruent morphological characters altogether is currently a common practice when reconstructing phylogenetic relationships. Ignoring incongruence may inflate the confidence in reconstructing relationships, particularly for the placement of highly derived and ecologically specialized taxa, such as among australosphenidans (particularly, crown monotremes), haramiyidans, and multituberculates. The alternative placement of these highly derived clades can alter the taxonomic constituency and temporal origin of the mammalian crown group. Based on prior hypotheses and correlated homoplasy analyses, we identified cheek teeth and shoulder girdle character complexes as having a high potential to introduce phylogenetic error. We showed that incongruence among mandibulodental, cranial, and postcranial anatomical partitions for the placement of the australosphenidans, haramiyids, and multituberculates could largely be explained by apparently non-phylogenetic covariance from cheek teeth and shoulder girdle characters. Excluding these character complexes brought agreement between anatomical regions and improved the confidence in tree topology. These results emphasize the importance of considering and ameliorating major sources of bias in morphological data, and we anticipate that these will be valuable for confidently integrating morphological and molecular data in phylogenetic and dating analyses.
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Affiliation(s)
- Mélina A. Celik
- School of Biology and Environmental Science, Queensland University of Technology, Brisbane, QLD, Australia
| | - Matthew J. Phillips
- School of Biology and Environmental Science, Queensland University of Technology, Brisbane, QLD, Australia
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27
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Anthwal N, Fenelon JC, Johnston SD, Renfree MB, Tucker AS. Transient role of the middle ear as a lower jaw support across mammals. eLife 2020; 9:e57860. [PMID: 32600529 PMCID: PMC7363448 DOI: 10.7554/elife.57860] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Accepted: 06/17/2020] [Indexed: 12/14/2022] Open
Abstract
Mammals articulate their jaws using a novel joint between the dentary and squamosal bones. In eutherian mammals, this joint forms in the embryo, supporting feeding and vocalisation from birth. In contrast, marsupials and monotremes exhibit extreme altriciality and are born before the bones of the novel mammalian jaw joint form. These mammals need to rely on other mechanisms to allow them to feed. Here, we show that this vital function is carried out by the earlier developing, cartilaginous incus of the middle ear, abutting the cranial base to form a cranio-mandibular articulation. The nature of this articulation varies between monotremes and marsupials, with juvenile monotremes retaining a double articulation, similar to that of the fossil mammaliaform Morganucodon, while marsupials use a versican-rich matrix to stabilise the jaw against the cranial base. These findings provide novel insight into the evolution of mammals and the changing relationship between the jaw and ear.
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Affiliation(s)
- Neal Anthwal
- Centre for Craniofacial and Regenerative Biology, King's College LondonLondonUnited Kingdom
| | - Jane C Fenelon
- School of BioSciences, University of MelbourneVictoriaAustralia
| | - Stephen D Johnston
- School of Agriculture and Food Sciences, University of QueenslandGattonAustralia
| | | | - Abigail S Tucker
- Centre for Craniofacial and Regenerative Biology, King's College LondonLondonUnited Kingdom
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28
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Le Maître A, Grunstra NDS, Pfaff C, Mitteroecker P. Evolution of the Mammalian Ear: An Evolvability Hypothesis. Evol Biol 2020; 47:187-192. [PMID: 32801400 PMCID: PMC7399675 DOI: 10.1007/s11692-020-09502-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 05/12/2020] [Indexed: 11/29/2022]
Abstract
Encapsulated within the temporal bone and comprising the smallest elements of the vertebrate skeleton, the ear is key to multiple senses: balance, posture control, gaze stabilization, and hearing. The transformation of the primary jaw joint into the mammalian ear ossicles is one of the most iconic transitions in vertebrate evolution, but the drivers of this complex evolutionary trajectory are not fully understood. We propose a novel hypothesis: The incorporation of the bones of the primary jaw joint into the middle ear has considerably increased the genetic, regulatory, and developmental complexity of the mammalian ear. This increase in the number of genetic and developmental factors may, in turn, have increased the evolutionary degrees of freedom for independent adaptations of the different functional ear units. The simpler ear anatomy in birds and reptiles may be less susceptible to developmental instabilities and disorders than in mammals but also more constrained in its evolution. Despite the tight spatial entanglement of functional ear components, the increased "evolvability" of the mammalian ear may have contributed to the evolutionary success and adaptive diversification of mammals in the vast diversity of ecological and behavioral niches observable today. A brief literature review revealed supporting evidence for this hypothesis.
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Affiliation(s)
- Anne Le Maître
- Department of Evolutionary Biology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
- Department of Palaeontology, University of Vienna, Vienna, Austria
- PALEVOPRIM - UMR 7262CNRS INEE, Université de Poitiers, Poitiers, France
| | - Nicole D. S. Grunstra
- Department of Evolutionary Biology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
- KLI Institute for Evolution and Cognition Research, Klosterneuburg, Austria
- Mammal Collection, Natural History Museum Vienna, Vienna, Austria
| | - Cathrin Pfaff
- Department of Palaeontology, University of Vienna, Vienna, Austria
| | - Philipp Mitteroecker
- Department of Evolutionary Biology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
- KLI Institute for Evolution and Cognition Research, Klosterneuburg, Austria
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Anthwal N, Tucker AS. The TMJ Disc Is a Common Ancestral Feature in All Mammals, as Evidenced by the Presence of a Rudimentary Disc During Monotreme Development. Front Cell Dev Biol 2020; 8:356. [PMID: 32509783 PMCID: PMC7248220 DOI: 10.3389/fcell.2020.00356] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 04/21/2020] [Indexed: 12/14/2022] Open
Abstract
The novel mammalian jaw joint, known in humans as the temporomandibular joint or TMJ, is cushioned by a fibrocartilage disc. This disc is secondarily absent in therian mammals that have lost their dentition, such as giant anteaters and some baleen whales. The disc is also absent in all monotremes. However, it is not known if the absence in monotremes is secondary to the loss of dentition, or if it is an ancestral absence. We use museum held platypus and echidna histological sections to demonstrate that the developing monotreme jaw joint forms a disc primordium that fails to mature and become separated from the mandibular condyle. We then show that monotreme developmental anatomy is similar to that observed in transgenic mouse mutants with reduced cranial musculature. We therefore suggest that the absence of the disc on monotremes is a consequence of the changes in jaw musculature associated with the loss of adult teeth. Taken together, these data indicate that the ancestors of extant monotremes likely had a jaw joint disc, and that the disc evolved in the last common ancestor of all mammals.
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Affiliation(s)
- Neal Anthwal
- Centre for Craniofacial and Regenerative Biology, King’s College London, London, United Kingdom
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30
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31
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Affiliation(s)
- Julia A Schultz
- Rheinische Friedrich-Wilhelms-Universität Bonn, Institut für Geowissenschaften, Bonn, Germany.
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32
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Meng J, Mao F, Han G, Zheng X, Wang X, Wang Y. A comparative study on auditory and hyoid bones of Jurassic euharamiyidans and contrasting evidence for mammalian middle ear evolution. J Anat 2020; 236:50-71. [PMID: 31498899 PMCID: PMC6904648 DOI: 10.1111/joa.13083] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/06/2019] [Indexed: 12/31/2022] Open
Abstract
The holotypes of euharamiyidan Arboroharamiya allinhopsoni and Arboroharamiya jenkinsi preserve the auditory and hyoid bones, respectively. With additional structures revealed by micro-computerized tomography (CT) and X-ray micro-computed laminography (CL), we provide a detailed description of these minuscule bones. The stapes in the two species of Arboroharamiya are similar in having a strong process for insertion of the stapedius muscle. The incus is similar in having an almond-shaped body and a slim short process, in addition to a robust stapedial process with a short lenticular process preserved in A. allinhopsoni. The plate-like ectotympanic in the two species of Arboroharamiya is similar and comparable to that of Qishou jizantang. The surangular in the two species has a fan-shaped body and a needle-shaped anterior process. The malleus, ectotympanic, and surangular are fully detached from the dentary and should have functioned exclusively for hearing. All the auditory bones of Arboroharamiya display unique features unknown in other mammaliaforms. Moreover, hyoid elements are found in the two species of Arboroharamiya and co-exist with the five auditory bones in the holotype of A. allinhopsoni. The element interpreted as the stylohyal is similar to the bone identified as the ectotympanic in Vilevolodon. We reconstruct the auditory apparatus of Arboroharamiya and compare it with that of Vilevolodon as well as those in extant mammals and basal mammaliaforms. The comparison shows diverse morphological patterns of the auditory region in mammaliaforms. In particular, those of Vilevolodon and Arboroharamiya differ significantly: the former has a mandibular middle ear, whereas the latter possesses a definitive mammalian middle ear. It is puzzling that the two sympatric and dentally similar taxa have such different auditory apparatuses. In light of the available evidence, we argue that the mandibular middle ear reconstructed in Vilevolodon encounters many problems, and the so-called ectotympanic in Vilevolodon may be interpreted as a stylohyal; thus, the dilemma can be resolved.
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Affiliation(s)
- Jin Meng
- Division of PaleontologyAmerican Museum of Natural HistoryNew YorkNYUSA
- Earth and Environmental SciencesGraduate CenterCity University of New YorkNew YorkNYUSA
| | - Fangyuan Mao
- Division of PaleontologyAmerican Museum of Natural HistoryNew YorkNYUSA
- Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of SciencesInstitute of Vertebrate Paleontology and PaleoanthropologyChinese Academy of SciencesBeijingChina
- CAS Center for Excellence in Life and PaleoenvironmentBeijingChina
| | - Gang Han
- Paleontology CenterBohai UniversityJinzhouChina
- Hainan Tropical Ocean UniversitySanyaChina
| | - Xiao‐Ting Zheng
- Institute of Geology and PaleontologyLinyi UniversityLinyiChina
- Shandong Tianyu Museum of NaturePingyiChina
| | - Xiao‐Li Wang
- Institute of Geology and PaleontologyLinyi UniversityLinyiChina
- Shandong Tianyu Museum of NaturePingyiChina
| | - Yuanqing Wang
- Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of SciencesInstitute of Vertebrate Paleontology and PaleoanthropologyChinese Academy of SciencesBeijingChina
- CAS Center for Excellence in Life and PaleoenvironmentBeijingChina
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Cretaceous fossil reveals a new pattern in mammalian middle ear evolution. Nature 2019; 576:102-105. [DOI: 10.1038/s41586-019-1792-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 10/23/2019] [Indexed: 11/09/2022]
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de Simão-Oliveira D, Kerber L, L Pinheiro F. Endocranial morphology of the Brazilian Permian dicynodont Rastodon procurvidens (Therapsida: Anomodontia). J Anat 2019; 236:384-397. [PMID: 31670465 DOI: 10.1111/joa.13107] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/20/2019] [Indexed: 12/18/2022] Open
Abstract
Dicynodontia is a major clade of terrestrial tetrapods that greatly diversified during the Permian and Triassic periods, reaching a worldwide distribution. In this study, the endocranial cavity of the Brazilian Permian dicynodont Rastodon procurvidens is described based on a digital endocast obtained using digital imaging (X-ray computed tomography) and 3D modeling. It was possible to reconstruct the brain, olfactory bulbs, inner ear, some neurovascular canals, cranial nerves, the nasal cavity, and the maxillary recesses. The endocast of R. procurvidens preserves a typical plesiomorphic morphology of non-mammaliaform therapsids, being predominantly tubular and displaying a relatively short and robust hindbrain. Encephalization quotients (EQs) were calculated for R. procurvidens, resulting in EQs of 0.09 ± 0.03 and 0.13 ± 0.05 (Jerison's EQ and Manger's EQ, respectively). Finally, some biological implications of the endocast morphology were inferred for R. procurvidens. Its inner ear is especially small, and its orientation implies a slightly downturned head posture in life. Furthermore, the presence of uncompressed maxillary recesses in R. procurvidens indicates a correlation between the enlargement of the recesses and the reduction of the tusks, also seen in other dicynodonts with reduced tusks.
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Affiliation(s)
- Daniel de Simão-Oliveira
- Laboratório de Paleobiologia, Programa de Pós-Graduação em Ciências Biológicas, Universidade Federal do Pampa (Unipampa), São Gabriel, Rio Grande do Sul, Brazil.,Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia (CAPPA), Programa de Pós-Graduação em Biodiversidade Animal, Universidade Federal de Santa Maria (UFSM), São João do Polêsine, Rio Grande do Sul, Brazil
| | - Leonardo Kerber
- Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia (CAPPA), Programa de Pós-Graduação em Biodiversidade Animal, Universidade Federal de Santa Maria (UFSM), São João do Polêsine, Rio Grande do Sul, Brazil
| | - Felipe L Pinheiro
- Laboratório de Paleobiologia, Programa de Pós-Graduação em Ciências Biológicas, Universidade Federal do Pampa (Unipampa), São Gabriel, Rio Grande do Sul, Brazil
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Mourlam MJ, Orliac MJ. Early evolution of the ossicular chain in Cetacea: into the middle ear gears of a semi-aquatic protocetid whale. Proc Biol Sci 2019; 286:20191417. [PMID: 31575370 DOI: 10.1098/rspb.2019.1417] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Modifications of the morphology and acoustic properties of the ossicular chain are among the major changes that accompanied the adaptation of Cetacea to the aquatic environment. Thus, data on the middle ear ossicles of early whales are crucial clues to understand the first steps of the emblematic terrestrial/aquatic transition that occurred in that group. Yet, the delicate nature and very small size of these bones make their preservation in the fossil record extremely rare. Due to the scarcity of available data, major questions remain concerning the sound transmission pathways in early non-fully aquatic whales. Virtual reconstruction of a partially complete ossicular chain of an Eocene protocetid whale documents for the first time the three ossicles of a semi-aquatic archaeocete. Contrary to previous hypotheses, these ossicles present different evolutionary patterns, showing that the ossicular chain does not act as a single morphological module. Functional analyses of the different middle ear units highlight a mosaic pattern of terrestrial and aquatic signatures. This integrative anatomical and functional study brings strong evidence that protocetids were adapted to their dual acoustic environment with efficient hearing in both air and water.
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Affiliation(s)
- Mickaël J Mourlam
- Institut des Sciences de l'Évolution, UMR 5554 CNRS, IRD, EPHE, Université de Montpellier, Place Eugène Bataillon, 34095 Montpellier cedex 5, France
| | - Maeva J Orliac
- Institut des Sciences de l'Évolution, UMR 5554 CNRS, IRD, EPHE, Université de Montpellier, Place Eugène Bataillon, 34095 Montpellier cedex 5, France
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36
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Harper T, Rougier GW. Petrosal morphology and cochlear function in Mesozoic stem therians. PLoS One 2019; 14:e0209457. [PMID: 31412094 PMCID: PMC6693738 DOI: 10.1371/journal.pone.0209457] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Accepted: 06/07/2019] [Indexed: 11/19/2022] Open
Abstract
Here we describe the bony anatomy of the inner ear and surrounding structures seen in three plesiomorphic crown mammalian petrosal specimens. Our study sample includes the triconodont Priacodon fruitaensis from the Upper Jurassic of North America, and two isolated stem therian petrosal specimens colloquially known as the Höövör petrosals, recovered from Aptian-Albian sediments in Mongolia. The second Höövör petrosal is here described at length for the first time. All three of these petrosals and a comparative sample of extant mammalian taxa have been imaged using micro-CT, allowing for detailed anatomical descriptions of the osteological correlates of functionally significant neurovascular features, especially along the abneural wall of the cochlear canal. The high resolution imaging provided here clarifies several hypotheses regarding the mosaic evolution of features of the cochlear endocast in early mammals. In particular, these images demonstrate that the membranous cochlear duct adhered to the bony cochlear canal abneurally to a secondary bony lamina before the appearance of an opposing primary bony lamina or tractus foraminosus. Additionally, while corroborating the general trend of reduction of venous sinuses and plexuses within the pars cochlearis seen in crownward mammaliaforms generally, the Höövör petrosals show the localized enlargement of a portion of the intrapetrosal venous plexus. This new vascular feature is here interpreted as the bony accommodation for the vein of cochlear aqueduct, a structure that is solely, or predominantly, responsible for the venous drainage of the cochlear apparatus in extant therians. Given that our fossil stem therian inner ear specimens appear to have very limited high-frequency capabilities, the development of these modern vascular features of the cochlear endocast suggest that neither the initiation or enlargement of the stria vascularis (a unique mammalian organ) was originally associated with the capacity for high-frequency hearing or precise sound-source localization.
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Affiliation(s)
- Tony Harper
- Center for Functional Anatomy and Evolution, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Guillermo W. Rougier
- Department of Anatomical Sciences and Neurobiology, University of Louisville, Louisville, Kentucky, United States of America
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Wallace RVS, Martínez R, Rowe T. First record of a basal mammaliamorph from the early Late Triassic Ischigualasto Formation of Argentina. PLoS One 2019; 14:e0218791. [PMID: 31390368 PMCID: PMC6685608 DOI: 10.1371/journal.pone.0218791] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 06/06/2019] [Indexed: 12/03/2022] Open
Abstract
We describe a new probainognathian cynodont, Pseudotherium argentinus, from the early Late Triassic Ischigualasto Formation of Argentina. Pseudotherium adds to a growing assemblage of small Triassic cynodonts that offers new insight into events leading up to the origin of crown Mammalia and the successively more inclusive Mammaliaformes and Mammaliamorpha. Using high-resolution X-ray computed tomography, we illustrate and describe the holotype and only known specimen, which consists of a well-preserved isolated skull. It preserves apomorphic features of the orbit and braincase. Prefrontal and vestigial postorbital bones are present, despite the absence of an ossified postorbital bar. As in Brasilitherium riograndensis, thin turbinal-like bones are present in the nasopharyngeal passage, and we discuss impediments to establishing their identity and function. Compared to more basal cynodonts, the cochlea is elongated but uncoiled and in this and other features it resembles basal mammaliamorphs. Our analysis found weak support for Pseudotherium as the sister taxon of Tritylodontidae. However, a broader assessment of its relationships in light of additional character data from the literature and unpublished computed tomography data suggest that it may be more realistic to view the relationships of Pseudotherium as an unresolved polytomy with tritylodontids, and the taxa referred to as tritheledontids and brasilodontids (groups of variable membership and questionable monophyly). Thus, Pseudotherium may lie just inside or just outside of Mammaliamorpha, and there is also weak character support for its sister taxon relationship with Brasilitherium. Our results amplify previous conclusions that phylogenetic relationships in this adaptive radiation of small cynodonts will remain somewhat uncertain until more complete specimens are recovered, and until high-resolution CT scans of existing specimens become available to the larger community. Toward that goal, we make the CT dataset for the holotype of Pseudotherium argentinus publically available under a Creative Commons license at www.DigiMorph.org.
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Affiliation(s)
- Rachel V. S. Wallace
- Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas, United States of America
| | - Ricardo Martínez
- División Paleontologia de Vertebrados, Instituto y Museo de Ciencias Naturales, Universidad Nacional de San Juan, San Juan, Argentina
| | - Timothy Rowe
- Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas, United States of America
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38
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Pfaff C, Schultz JA, Schellhorn R. The vertebrate middle and inner ear: A short overview. J Morphol 2019; 280:1098-1105. [PMID: 30117612 PMCID: PMC6766920 DOI: 10.1002/jmor.20880] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Revised: 06/30/2018] [Accepted: 07/05/2018] [Indexed: 01/11/2023]
Abstract
The evolution of the various hearing adaptations is connected to major structural changes in nearly all groups of vertebrates. Besides hearing, the detection of acceleration and orientation in space are key functions of this mechanosensory system. The symposium "show me your ear - the inner and middle ear in vertebrates" held at the 11th International Congress of Vertebrate Morphology (ICVM) 2016 in Washington, DC (USA) intended to present current research addressing adaptation and evolution of the vertebrate otic region, auditory ossicles, vestibular system, and hearing physiology. The symposium aimed at an audience with interest in hearing research focusing on morphological, functional, and comparative studies. The presented talks and posters lead to the contributions of this virtual issue highlighting recent advances in the vertebrate balance and hearing system. This article serves as an introduction to the virtual issue contributions and intends to give a short overview of research papers focusing on vertebrate labyrinth and middle ear related structures in past and recent years.
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Affiliation(s)
- Cathrin Pfaff
- University of Vienna, Department of PalaeontologyViennaAustria
| | - Julia A. Schultz
- University of Chicago, Department of Organismal Biology and AnatomyChicagoIllinoisUSA
- Rheinische Friedrich‐Wilhelms‐Universität Bonn, Steinmann Institut für Geologie, Mineralogie und PaläontologieBonnGermany
| | - Rico Schellhorn
- Rheinische Friedrich‐Wilhelms‐Universität Bonn, Steinmann Institut für Geologie, Mineralogie und PaläontologieBonnGermany
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39
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Navarro-Díaz A, Esteve-Altava B, Rasskin-Gutman D. Disconnecting bones within the jaw-otic network modules underlies mammalian middle ear evolution. J Anat 2019; 235:15-33. [PMID: 30977522 DOI: 10.1111/joa.12992] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/06/2019] [Indexed: 01/08/2023] Open
Abstract
The origin of the mammalian middle ear ossicles from the craniomandibular articulation of their synapsid ancestors is a key event in the evolution of vertebrates. The richness of the fossil record and the multitude of developmental studies have provided a stepwise reconstruction of this evolutionary innovation, highlighting the homology between the quadrate, articular, pre-articular and angular bones of early synapsids with the incus, malleus, gonial and ectotympanic bones of derived mammals, respectively. There are several aspects involved in this functional exaptation: (i) an increase of the masticatory musculature; (ii) the separation of the quadrate bone from the cranium; and (iii) the disconnection of the post-dentary bones from the dentary. Here, we compared the jaw-otic complex for 43 synapsid taxa using anatomical network analysis, showing that the disconnection of mandibular bones was a key step in the mammalian middle ear evolution, changing the skull anatomical modularity concomitant to the acquisition of new functions. Furthermore, our analysis allows the identification of three types of anatomical modules evolving through five evolutionary stages during the anatomical transformation of the jawbones into middle ear bones, with the ossification and degradation of Meckel's cartilage in mammals as the key ontogenetic event leading the change of anatomical modularity.
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Affiliation(s)
- Aitor Navarro-Díaz
- Paleobiology and Theoretical biology (Theoretical Biology), Cavanilles Institute of Biodiversity and Evolutionary Biology, University of Valencia, Valencia, Spain
| | - Borja Esteve-Altava
- Institute of Evolutionary Biology (UPF-CSIC), Department of Experimental and Health Sciences, University Pompeu Fabra, Barcelona, Spain
| | - Diego Rasskin-Gutman
- Paleobiology and Theoretical biology (Theoretical Biology), Cavanilles Institute of Biodiversity and Evolutionary Biology, University of Valencia, Valencia, Spain
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40
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Lessner EJ, Gant CA, Hieronymus TL, Vickaryous MK, Holliday CM. Anatomy and Ontogeny of the Mandibular Symphysis in Alligator mississippiensis. Anat Rec (Hoboken) 2019; 302:1696-1708. [PMID: 30883043 DOI: 10.1002/ar.24116] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 11/14/2018] [Accepted: 12/10/2018] [Indexed: 01/13/2023]
Abstract
Crocodylians evolved some of the most characteristic skulls of the animal kingdom with specializations for semiaquatic and ambush lifestyles, resulting in a feeding apparatus capable of tolerating high biomechanical loads and bite forces and a head with a derived sense of trigeminal-nerve-mediated touch. The mandibular symphysis accommodates these specializations being both at the end of a biomechanical lever and an antenna for sensation. Little is known about the anatomy of the crocodylian mandibular symphysis, hampering our understanding of form, function, and evolution of the joint in extant and extinct lineages. We explore mandibular symphysis anatomy of an ontogenetic series of Alligator mississippiensis using imaging, histology, and whole mount methods. Complex sutural ligaments emanating about a midline-fused Meckel's cartilage bridge the symphysis. These tissues organize during days 37-42 of in ovo development. However, interdigitations do not manifest until after hatching. These soft tissues leave a hub and spoke-like bony morphology of the symphyseal plate, which never fuses. Interdigitation morphology varies within the symphysis suggesting differential loading about the joint. Neurovascular canals extend throughout the mandibles to alveoli, integument, and bone adjacent to the symphysis. These features suggest the Alligator mandibular symphysis offers compliance in an otherwise rigid skull. We hypothesize a fused Meckel's cartilage offers stiffness in hatchling mandibles prior to the development of organized sutural ligaments and mineralized bone while offering a scaffold for somatic growth. The porosity of the dentaries due to neurovascular tissues likely allows transmission of sensory and proprioceptive information from the surroundings and the loaded symphysis. Anat Rec, 302:1696-1708, 2019. © 2019 American Association for Anatomy.
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Affiliation(s)
- Emily J Lessner
- Program in Integrative Anatomy, Department of Pathology and Anatomical Sciences, University of Missouri Medical School, Columbia, Missouri
| | - Cortaiga A Gant
- Program in Integrative Anatomy, Department of Pathology and Anatomical Sciences, University of Missouri Medical School, Columbia, Missouri
| | - Tobin L Hieronymus
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, Ohio
| | - Matthew K Vickaryous
- Department of Biomedical Sciences, University of Guelph, Guelpgh, Ontario, Canada
| | - Casey M Holliday
- Program in Integrative Anatomy, Department of Pathology and Anatomical Sciences, University of Missouri Medical School, Columbia, Missouri
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Lautenschlager S, Gill PG, Luo ZX, Fagan MJ, Rayfield EJ. The role of miniaturization in the evolution of the mammalian jaw and middle ear. Nature 2018; 561:533-537. [PMID: 30224748 DOI: 10.1038/s41586-018-0521-4] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 08/13/2018] [Indexed: 11/09/2022]
Abstract
The evolution of the mammalian jaw is one of the most important innovations in vertebrate history, and underpins the exceptional radiation and diversification of mammals over the last 220 million years1,2. In particular, the transformation of the mandible into a single tooth-bearing bone and the emergence of a novel jaw joint-while incorporating some of the ancestral jaw bones into the mammalian middle ear-is often cited as a classic example of the repurposing of morphological structures3,4. Although it is remarkably well-documented in the fossil record, the evolution of the mammalian jaw still poses the paradox of how the bones of the ancestral jaw joint could function both as a joint hinge for powerful load-bearing mastication and as a mandibular middle ear that was delicate enough for hearing. Here we use digital reconstructions, computational modelling and biomechanical analyses to demonstrate that the miniaturization of the early mammalian jaw was the primary driver for the transformation of the jaw joint. We show that there is no evidence for a concurrent reduction in jaw-joint stress and increase in bite force in key non-mammaliaform taxa in the cynodont-mammaliaform transition, as previously thought5-8. Although a shift in the recruitment of the jaw musculature occurred during the evolution of modern mammals, the optimization of mandibular function to increase bite force while reducing joint loads did not occur until after the emergence of the neomorphic mammalian jaw joint. This suggests that miniaturization provided a selective regime for the evolution of the mammalian jaw joint, followed by the integration of the postdentary bones into the mammalian middle ear.
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Affiliation(s)
- Stephan Lautenschlager
- School of Earth Sciences, University of Bristol, Bristol, UK. .,School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UK.
| | - Pamela G Gill
- School of Earth Sciences, University of Bristol, Bristol, UK.,Earth Science Department, The Natural History Museum, London, UK
| | - Zhe-Xi Luo
- Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL, USA
| | - Michael J Fagan
- School of Engineering and Computer Science, University of Hull, Hull, UK
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An Early Cretaceous eutherian and the placental–marsupial dichotomy. Nature 2018; 558:390-395. [DOI: 10.1038/s41586-018-0210-3] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 05/10/2018] [Indexed: 11/08/2022]
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Schultz JA, Ruf I, Martin T. Oldest known multituberculate stapes suggests an asymmetric bicrural pattern as ancestral for Multituberculata. Proc Biol Sci 2018; 285:rspb.2017.2779. [PMID: 29467266 DOI: 10.1098/rspb.2017.2779] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 01/26/2018] [Indexed: 11/12/2022] Open
Abstract
Middle ear ossicles (malleus, incus, stapes) are known for few multituberculate taxa, and three different stapedial morphotypes have been suggested: (i) slender, columelliform and microperforate, (ii) robust and rod-like, and (iii) bicrural. Reinvestigation of Upper Jurassic (Kimmeridgian) mammalian petrosals from the Guimarota coal mine in central Portugal (Western Europe) revealed an asymmetric bicrural stapes (ABS) in the paulchoffatiid Pseudobolodon oreas The middle ear ossicles displaced inside the osseous vestibule were detected by a µCT analysis. The Kimmeridgian age of the Guimarota stapes exceeds the stapes from the Early Cretaceous (Barremian) of Asia (about 122-124 Ma) by approximately 30 Myr, and is only slightly younger than the stapes of the recently described Oxfordian euharamiyidan Arboroharamiya allinhopsoni The Guimarota stapes indicates that the stapes of Lambdopsalis, described as columelliform and microperforate (small stapedial foramen), does not represent a general condition for multituberculates. The stapes of Pseudobolodon is bicrural, the anterior crus sits centrally on the oval footplate, and the stapedial head is simple and smaller than the footplate. We hypothesize that the ABS evolved from the symmetric bicrural stapes (SBS) of non-mammaliaform cynodonts. The ABS appears to be the ancestral morphotype of the mammalian SBS, and the mammalian columelliform imperforate stapes.
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Affiliation(s)
- Julia A Schultz
- Department of Organismal Biology and Anatomy, The University of Chicago, Chicago, IL 60637, USA .,Steinmann-Institut für Geologie, Mineralogie und Paläontologie, Universität Bonn, 53115 Bonn, Germany
| | - Irina Ruf
- Abteilung Messelforschung und Mammalogie, Senckenberg Forschungsinstitut und Naturmuseum Frankfurt, 60325 Frankfurt am Main, Germany
| | - Thomas Martin
- Steinmann-Institut für Geologie, Mineralogie und Paläontologie, Universität Bonn, 53115 Bonn, Germany
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Morphology of the Middle Ear Ossicles in the Rodent Perimys(Neoepiblemidae) and a Comprehensive Anatomical and Morphometric Study of the Phylogenetic Transformations of these Structures in Caviomorphs. J MAMM EVOL 2018. [DOI: 10.1007/s10914-017-9422-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Re-examination of the Jurassic Mammaliaform Docodon victor by Computed Tomography and Occlusal Functional Analysis. J MAMM EVOL 2017. [DOI: 10.1007/s10914-017-9418-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Ferner K, Schultz JA, Zeller U. Comparative anatomy of neonates of the three major mammalian groups (monotremes, marsupials, placentals) and implications for the ancestral mammalian neonate morphotype. J Anat 2017; 231:798-822. [PMID: 28960296 PMCID: PMC5696127 DOI: 10.1111/joa.12689] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/08/2017] [Indexed: 12/16/2022] Open
Abstract
The existing different modes of reproduction in monotremes, marsupials and placentals are the main source for our current understanding of the origin and evolution of the mammalian reproduction. The reproductive strategies and, in particular, the maturity states of the neonates differ remarkably between the three groups. Monotremes, for example, are the only extant mammals that lay eggs and incubate them for the last third of their embryonic development. In contrast, marsupials and placentals are viviparous and rely on intra-uterine development of the neonates via choriovitelline (mainly marsupials) and chorioallantoic (mainly placentals) placentae. The maturity of a newborn is closely linked to the parental care strategy once the neonate is born. The varying developmental degrees of neonates are the main focus of this study. Monotremes and marsupials produce highly altricial and nearly embryonic offspring. Placental mammals always give birth to more developed newborns with the widest range from altricial to precocial. The ability of a newborn to survive and grow in the environment it was born in depends highly on the degree of maturation of vital organs at the time of birth. Here, the anatomy of four neonates of the three major extant mammalian groups is compared. The basis for this study is histological and ultrastructural serial sections of a hatchling of Ornithorhynchus anatinus (Monotremata), and neonates of Monodelphis domestica (Marsupialia), Mesocricetus auratus (altricial Placentalia) and Macroscelides proboscideus (precocial Placentalia). Special attention was given to the developmental stages of the organs skin, lung, liver and kidney, which are considered crucial for the maintenance of vital functions. The state of the organs of newborn monotremes and marsupials are found to be able to support a minimum of vital functions outside the uterus. They are sufficient to survive, but without capacities for additional energetic challenges. The organs of the altricial placental neonate are further developed, able to support the maintenance of vital functions and short-term metabolic increase. The precocial placental newborn shows the most advanced state of organ development, to allow the maintenance of vital functions, stable thermoregulation and high energetic performance. The ancestral condition of a mammalian neonate is interpreted to be similar to the state of organ development found in the newborns of marsupials and monotremes. In comparison, the newborns of altricial and precocial placentals are derived from the ancestral state to a more mature developmental degree associated with advanced organ systems.
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Affiliation(s)
- Kirsten Ferner
- Leibniz‐Institut für Evolutions‐ und BiodiversitätsforschungMuseum für NaturkundeBerlinGermany
| | - Julia A. Schultz
- Department of Organismal Biology and AnatomyUniversity of ChicagoChicagoILUSA
| | - Ulrich Zeller
- Lebenswissenschaftliche FakultätFG Spezielle ZoologieAlbrecht Daniel Thaer‐Institut für Agrar‐ und GartenbauwissenschaftenHumboldt‐Universität zu BerlinBerlinGermany
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Tucker AS. Major evolutionary transitions and innovations: the tympanic middle ear. Philos Trans R Soc Lond B Biol Sci 2017; 372:rstb.2015.0483. [PMID: 27994124 PMCID: PMC5182415 DOI: 10.1098/rstb.2015.0483] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/14/2016] [Indexed: 01/08/2023] Open
Abstract
One of the most amazing transitions and innovations during the evolution of mammals was the formation of a novel jaw joint and the incorporation of the original jaw joint into the middle ear to create the unique mammalian three bone/ossicle ear. In this review, we look at the key steps that led to this change and other unusual features of the middle ear and how developmental biology has been providing an understanding of the mechanisms involved. This starts with an overview of the tympanic (air-filled) middle ear, and how the ear drum (tympanic membrane) and the cavity itself form during development in amniotes. This is followed by an investigation of how the ear is connected to the pharynx and the relationship of the ear to the bony bulla in which it sits. Finally, the novel mammalian jaw joint and versatile dentary bone will be discussed with respect to evolution of the mammalian middle ear.This article is part of the themed issue 'Evo-devo in the genomics era, and the origins of morphological diversity'.
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Affiliation(s)
- Abigail S Tucker
- Department of Craniofacial Development and Stem Cell Biology, King's College London, Floor 27 Guy's Hospital, London Bridge, London SE1 9RT, UK
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New evidence for mammaliaform ear evolution and feeding adaptation in a Jurassic ecosystem. Nature 2017; 548:326-329. [DOI: 10.1038/nature23483] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2016] [Accepted: 07/14/2017] [Indexed: 11/08/2022]
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Grossnickle DM. The evolutionary origin of jaw yaw in mammals. Sci Rep 2017; 7:45094. [PMID: 28322334 PMCID: PMC5359619 DOI: 10.1038/srep45094] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Accepted: 02/17/2017] [Indexed: 11/17/2022] Open
Abstract
Theria comprises all but three living mammalian genera and is one of the most ecologically pervasive clades on Earth. Yet, the origin and early history of therians and their close relatives (i.e., cladotherians) remains surprisingly enigmatic. A critical biological function that can be compared among early mammal groups is mastication. Morphometrics and modeling analyses of the jaws of Mesozoic mammals indicate that cladotherians evolved musculoskeletal anatomies that increase mechanical advantage during jaw rotation around a dorsoventrally-oriented axis (i.e., yaw) while decreasing the mechanical advantage of jaw rotation around a mediolaterally-oriented axis (i.e., pitch). These changes parallel molar transformations in early cladotherians that indicate their chewing cycles included significant transverse movement, likely produced via yaw rotation. Thus, I hypothesize that cladotherian molar morphologies and musculoskeletal jaw anatomies evolved concurrently with increased yaw rotation of the jaw during chewing cycles. The increased transverse movement resulting from yaw rotation may have been a crucial evolutionary prerequisite for the functionally versatile tribosphenic molar morphology, which underlies the molars of all therians and is retained by many extant clades.
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Affiliation(s)
- David M Grossnickle
- University of Chicago, Committee on Evolutionary Biology, Chicago, 60637, USA
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