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Fonseca PHM, Martinelli AG, Gill PG, Rayfield EJ, Schultz CL, Kerber L, Ribeiro AM, Soares MB. Anatomy of the maxillary canal of Riograndia guaibensis (Cynodontia, Probainognathia)-A prozostrodont from the Late Triassic of southern Brazil. Anat Rec (Hoboken) 2024. [PMID: 39039851 DOI: 10.1002/ar.25540] [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: 02/28/2024] [Revised: 06/24/2024] [Accepted: 07/02/2024] [Indexed: 07/24/2024]
Abstract
Investigating the evolutionary trajectory of synapsid sensory and cephalic systems is pivotal for understanding the emergence and diversification of mammals. Recent studies using CT-scanning to analyze the rostral foramina and maxillary canals morphology in fossilized specimens of probainognathian cynodonts have contributed to clarifying the homology and paleobiological interpretations of these structures. In the present work, μCT-scannings of three specimens of Riograndia guaibensis, an early Norian cynodont from southern Brazil, were analyzed and revealed an incomplete separation between the lacrimal and maxillary canals, with points of contact via non-ossified areas. While the maxillary canal exhibits a consistent morphological pattern with other Prozostrodontia, featuring three main branches along the lateral region of the snout, the rostral alveolar canal in Riograndia displays variability in the number of extra branches terminating in foramina on the lateral surface of the maxilla, showing differences among individuals and within the same skull. Additionally, pneumatization is observed in the anterior region of the skull, resembling similar structures found in reptiles and mammals. Through this pneumatization, certain branches originating from the maxillary canal extend to the canine alveolus. Further investigation is warranted to elucidate the functionality of this structure and its occurrence in other cynodont groups.
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Affiliation(s)
- Pedro Henrique Morais Fonseca
- Programa de Pós-Graduação em Geociências, Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Agustín Guillermo Martinelli
- CONICET-Sección Paleontología de Vertebrados, Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", Buenos Aires, Argentina
- Núcleo Milenio EVOTEM-Evolutionary Transitions of Early Mammals-ANID, Santiago, Chile
| | - Pamela G Gill
- Palaeobiology Research Group, School of Earth Sciences, University of Bristol, Life Sciences Building, Bristol, UK
- Earth Sciences Department, The Natural History Museum, London, UK
| | - Emily J Rayfield
- Palaeobiology Research Group, School of Earth Sciences, University of Bristol, Life Sciences Building, Bristol, UK
| | - Cesar Leandro Schultz
- Programa de Pós-Graduação em Geociências, Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Leonardo Kerber
- Centro de Apoio à Pesquisa Paleontológica, Universidade Federal de Santa Maria, São João do Polêsine, Brazil
| | - Ana Maria Ribeiro
- Programa de Pós-Graduação em Geociências, Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
- Seção de Paleontologia, Museu de Ciências Naturais, Secretaria do Meio Ambiente e Infraestrutura do Rio Grande do Sul, Porto Alegre, Brazil
| | - Marina Bento Soares
- Departamento de Geologia e Paleontologia, Museu Nacional, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
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Fonseca PHM, Martinelli AG, Gill PG, Rayfield EJ, Schultz CL, Kerber L, Ribeiro AM, Francischini H, Soares MB. New evidence from high-resolution computed microtomography of Triassic stem-mammal skulls from South America enhances discussions on turbinates before the origin of Mammaliaformes. Sci Rep 2024; 14:13817. [PMID: 38879680 PMCID: PMC11180108 DOI: 10.1038/s41598-024-64434-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Accepted: 06/10/2024] [Indexed: 06/19/2024] Open
Abstract
The nasal cavity of living mammals is a unique structural complex among tetrapods, acquired along a series of major morphological transformations that occurred mainly during the Mesozoic Era, within the Synapsida clade. Particularly, non-mammaliaform cynodonts document several morphological changes in the skull, during the Triassic Period, that represent the first steps of the mammalian bauplan. We here explore the nasal cavity of five cynodont taxa, namely Thrinaxodon, Chiniquodon, Prozostrodon, Riograndia, and Brasilodon, in order to discuss the main changes within this skull region. We did not identify ossified turbinals in the nasal cavity of these taxa and if present, as non-ossified structures, they would not necessarily be associated with temperature control or the development of endothermy. We do, however, notice a complexification of the cartilage anchoring structures that divide the nasal cavity and separate it from the brain region in these forerunners of mammals.
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Affiliation(s)
- Pedro H M Fonseca
- Programa de Pós-Graduação em Geociências, Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500, Bairro Agronomia, Porto Alegre, Rio Grande do Sul, 91501-970, Brazil.
| | - Agustín G Martinelli
- CONICET-Sección Paleontología de Vertebrados, Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", Av. Ángel Gallardo 470, C1405DJR, Buenos Aires, CABA, Argentina.
- Núcleo Milenio EVOTEM-Evolutionary Transitions of Early Mammals-ANID, Santiago, Chile.
| | - Pamela G Gill
- Palaeobiology Research Group, School of Earth Sciences, University of Bristol, Life Sciences Building, Bristol, BS8 1TQ, UK.
- Science Department, Natural History Museum, Cromwell Road, London, SW7 5HD, UK.
| | - Emily J Rayfield
- Palaeobiology Research Group, School of Earth Sciences, University of Bristol, Life Sciences Building, Bristol, BS8 1TQ, UK.
| | - Cesar L Schultz
- Programa de Pós-Graduação em Geociências, Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500, Bairro Agronomia, Porto Alegre, Rio Grande do Sul, 91501-970, Brazil
| | - Leonardo Kerber
- Centro de Apoio à Pesquisa Paleontológica, Universidade Federal de Santa Maria, São João do Polêsine, Brazil
| | - Ana Maria Ribeiro
- Programa de Pós-Graduação em Geociências, Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500, Bairro Agronomia, Porto Alegre, Rio Grande do Sul, 91501-970, Brazil
- Museu de Ciências Naturais/SEMA, Porto Algre, RS, Brazil
| | - Heitor Francischini
- Programa de Pós-Graduação em Geociências, Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500, Bairro Agronomia, Porto Alegre, Rio Grande do Sul, 91501-970, Brazil
| | - Marina B Soares
- Departamento de Geologia e Paleontologia, Museu Nacional, Universidade Federal do Rio de Janeiro, Quinta da Boa Vista s/n, São Cristovão, Rio de Janeiro, RJ, 20940-040, Brazil.
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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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Kaiuca JFL, Martinelli AG, Schultz CL, Fonseca PHM, Tavares WC, Soares MB. Weighing in on miniaturization: New body mass estimates for Triassic eucynodonts and analyses of body size evolution during the cynodont-mammal transition. Anat Rec (Hoboken) 2024; 307:1594-1612. [PMID: 38229416 DOI: 10.1002/ar.25377] [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: 09/30/2023] [Revised: 12/20/2023] [Accepted: 12/22/2023] [Indexed: 01/18/2024]
Abstract
Body size influences most aspects of an animal's biology, consequently, evolutionary diversification is often accompanied by differentiation of body sizes within a lineage. It is accepted that miniaturization, or the evolution of extremely small body sizes, played a key role in the origin and early evolution of different mammalian characters in non-mammaliaform cynodonts. However, while there are multiple studies on the biomechanical, behavioral, and physiological consequences of smaller sizes, few explore the evolutionary processes that lead to them. Here, we use body mass as a universal size measurement in phylogenetic comparative analyses to explore aspects of body size evolution in Cynodontia, focusing on the cynodont-mammal transition, and test the miniaturization hypothesis for the origin of Mammaliaformes. We estimated the body masses of 29 species, ranging from Theriocephalia to Mammaliaformes, providing the largest collection of Triassic cynodont body mass estimates that we know of, and used these estimates in analyses of disparity through time and RRphylo . Unexpectedly, our results did not support the miniaturization hypothesis. Even though cynodont body size disparity fell during the Late Triassic, and remained lower than expected under a purely Brownian motion model of evolution up until the Early Jurassic, we found that rates of body size evolution were significantly lower in prozostrodontians leading to the first Mammaliaformes than in other lineages. Evolution rates were higher in medium and large-sized taxa, indicating that size was changing more rapidly in those lineages and that small sizes were probably a persistent plesiomorphic character-state in Cynodontia.
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Affiliation(s)
- João Felipe Leal Kaiuca
- Programa de Pós-Graduação em Biodiversidade e Biologia Evolutiva, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Instituto de Biologia, Interbloco B/C, CCS, Rio de Janeiro, Brazil
- Núcleo Multidisciplinar de Pesquisa em Biologia, Campus UFRJ Duque de Caxias Professor Geraldo Cidade, Universidade Federal do Rio de Janeiro, Duque de Caxias, Brazil
- Departamento de Geologia e Paleontologia, Museu Nacional, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Agustín Guillermo Martinelli
- Sección Paleontología de Vertebrados, Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"-CONICET, Buenos Aires, Argentina
| | - Cesar Leandro Schultz
- Departamento de Paleontologia e Estratigrafia, Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Pedro Henrique Morais Fonseca
- Programa de Pós-Graduação em Geociências, Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - William Corrêa Tavares
- Programa de Pós-Graduação em Biodiversidade e Biologia Evolutiva, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Instituto de Biologia, Interbloco B/C, CCS, Rio de Janeiro, Brazil
- Núcleo Multidisciplinar de Pesquisa em Biologia, Campus UFRJ Duque de Caxias Professor Geraldo Cidade, Universidade Federal do Rio de Janeiro, Duque de Caxias, Brazil
| | - Marina Bento Soares
- Departamento de Geologia e Paleontologia, Museu Nacional, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
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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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Fostowicz-Frelik Ł, Tseng ZJ. The mammalian skull: development, structure and function. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220077. [PMID: 37183895 PMCID: PMC10184243 DOI: 10.1098/rstb.2022.0077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023] Open
Abstract
The mammalian skull is an informative and versatile study system critical to research efforts across the broad spectrum of molecular, cellular, organismal and evolutionary sciences. The amount of knowledge concerning mammalian skull continues to grow exponentially, fuelled by the advent of new research methods and new material. Computed microtomography, including X-ray imaging using synchrotron radiation, proved to be an important tool for the descriptive and quantitative analysis of cranial anatomy. A major conceptual change, namely combining genetics and development with evolution into 'evo-devo' studies, also contributed to our knowledge of the mammalian skull enormously. These advances, coupled with novel techniques now allow researchers to integrate the process of cranial development with data from the fossil record, which is also augmented by seminal discoveries from Africa, Asia and both Americas. However, for decades, there has been no comprehensive source covering fundamental aspects of this vibrant field of evolutionary biology. To address this gap, we offer in this theme issue a balanced mix of research papers and reviews from leading experts in the field and a younger generation of scientists from five continents. This article is part of the theme issue 'The mammalian skull: development, structure and function'.
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Affiliation(s)
- Łucja Fostowicz-Frelik
- Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL 60637, USA
- Institute of Paleobiology, Polish Academy of Sciences, 00-818 Warsaw, Poland
| | - Z Jack Tseng
- Department of Integrative Biology, University of California, Berkeley, CA 94720-3200, USA
- University of California Museum of Paleontology, Berkeley, CA 94720, USA
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