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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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2
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Pusch LC, Kammerer CF, Fröbisch J. The origin and evolution of Cynodontia (Synapsida, Therapsida): Reassessment of the phylogeny and systematics of the earliest members of this clade using 3D-imaging technologies. Anat Rec (Hoboken) 2024; 307:1634-1730. [PMID: 38444024 DOI: 10.1002/ar.25394] [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: 10/12/2023] [Revised: 01/13/2024] [Accepted: 01/14/2024] [Indexed: 03/07/2024]
Abstract
The origin of cynodonts, the group ancestral to and including mammals, is one of the major outstanding problems in therapsid evolution. One of the most troubling aspects of the cynodont fossil record is the lengthy Permian ghost lineage between the latest possible divergence from its sister group Therocephalia and the first appearance of definitive cynodonts in the late Permian. The absence of cynodonts and dominance of therocephalians in middle Permian strata has led some workers to argue that cynodonts evolved from within therocephalians, rendering the latter paraphyletic, but more recent analyses support the reciprocal monophyly of Cynodontia and Therocephalia. Furthermore, although a fundamental dichotomy in the derived subclade Eucynodontia is well-supported in cynodont phylogeny, the relationships of more stemward cynodonts from the late Permian and Early Triassic are unresolved. Here, we provide a re-evaluation of the phylogeny of Eutheriodontia (Cynodontia + Therocephalia) and an assessment of character evolution within the group. Using computed tomographic data derived from extensive sampling of the earliest known (late Permian and Early Triassic) cynodonts and selected exemplars of therocephalians and later (Middle Triassic onwards) cynodonts, we describe novel aspects of the endocranial anatomy of these animals. These data were incorporated into a new phylogenetic data set including a comprehensive sample of early cynodonts. Our phylogenetic analyses support some results previously recovered by other authors, but recover therocephalians as paraphyletic with regards to cynodonts, with cynodonts and eutherocephalians forming a clade to the exclusion of the "basal therocephalian" families Lycosuchidae and Scylacosauridae. Though both conservatism and homoplasy mark the endocranial anatomy of early non-mammalian cynodonts, we were able to identify several new endocranial synapomorphies for eutheriodont subclades and recovered generally better-supported topologies than previous analyses using primarily external craniodental characters.
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Affiliation(s)
- Luisa C Pusch
- Museum für Naturkunde, Leibniz-Institut füsr Evolutions- und Biodiversitätsforschung, Berlin, Germany
- Institut für Biologie, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Christian F Kammerer
- North Carolina Museum of Natural Sciences, Raleigh, North Carolina, USA
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
| | - Jörg Fröbisch
- Museum für Naturkunde, Leibniz-Institut füsr Evolutions- und Biodiversitätsforschung, Berlin, Germany
- Institut für Biologie, Humboldt-Universität zu Berlin, Berlin, Germany
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
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3
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Kerber L, Roese-Miron L, Bubadué JM, Martinelli AG. Endocranial anatomy of the early prozostrodonts (Eucynodontia: Probainognathia) and the neurosensory evolution in mammal forerunners. Anat Rec (Hoboken) 2024; 307:1442-1473. [PMID: 37017195 DOI: 10.1002/ar.25215] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 03/09/2023] [Accepted: 03/09/2023] [Indexed: 04/06/2023]
Abstract
Prozostrodon brasiliensis and Therioherpeton cargnini are non-mammaliaform cynodonts that lived ~233 million years ago (late Carnian, Late Triassic) in western Gondwana. They represent some of the earliest divergent members of the clade Prozostrodontia, which includes "tritheledontids", tritylodontids, "brasilodontids", and mammaliaforms (including Mammalia as crown group). Here, we studied the endocranial anatomy (cranial endocast, nerves, vessels, ducts, ear region, and nasal cavity) of these two species. Our findings suggest that during the Carnian, early prozostrodonts had a brain with well-developed olfactory bulbs, expanded cerebral hemispheres divided by the interhemispheric sulcus, and absence of an unossified zone and pineal body. The morphology of the maxillary canal represents the necessary condition for the presence of facial vibrissae. A slight decrease in encephalization is observed at the origin of the clade Prozostrodontia. This new anatomical information provides evidence for the evolution of endocranial traits of the first prozotrodonts, a Late Triassic lineage that culminated in the origin of mammals.
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Affiliation(s)
- Leonardo Kerber
- Programa de Pós-Graduação em Biodiversidade Animal, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil
- Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia, Universidade Federal de Santa Maria (CAPPA/UFSM), São João do Polêsine, RS, Brazil
| | - Lívia Roese-Miron
- Programa de Pós-Graduação em Biodiversidade Animal, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil
- Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia, Universidade Federal de Santa Maria (CAPPA/UFSM), São João do Polêsine, RS, Brazil
| | - Jamile M Bubadué
- Laboratorio de Ciências Ambientais, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brazil
| | - Agustín G Martinelli
- Sección Paleontologia de Vertebrados, Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", Buenos Aires, Argentina
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Singh SA, Elsler A, Stubbs TL, Rayfield EJ, Benton MJ. Predatory synapsid ecomorphology signals growing dynamism of late Palaeozoic terrestrial ecosystems. Commun Biol 2024; 7:201. [PMID: 38368492 PMCID: PMC10874460 DOI: 10.1038/s42003-024-05879-2] [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: 12/16/2022] [Accepted: 02/01/2024] [Indexed: 02/19/2024] Open
Abstract
Terrestrial ecosystems evolved substantially through the Palaeozoic, especially the Permian, gaining much new complexity, especially among predators. Key among these predators were non-mammalian synapsids. Predator ecomorphology reflect interactions with prey and competitors, which are key controls on carnivore diversity and ecology. Therefore, carnivorous synapsids may offer insight on wider ecological evolution as the first complex, tetrapod-dominated, terrestrial ecosystems formed through the late Palaeozoic. Using morphometric and phylogenetic comparative methods, we chart carnivorous synapsid trophic morphology from the latest Carboniferous to the earliest Triassic (307-251.2 Ma). We find a major morphofunctional shift in synapsid carnivory between the early and middle Permian, via the addition of new feeding modes increasingly specialised for greater biting power or speed that captures the growing antagonism and dynamism of terrestrial tetrapod predator-prey interactions. The further evolution of new hypo- and hypercarnivorous synapsids highlight the nascent intrinsic pressures and complexification of terrestrial ecosystems across the mid-late Permian.
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Affiliation(s)
- Suresh A Singh
- School of Earth Sciences, University of Bristol, Life Sciences Building, Tyndall Avenue, Bristol, BS8 1TQ, UK.
| | - Armin Elsler
- School of Earth Sciences, University of Bristol, Life Sciences Building, Tyndall Avenue, Bristol, BS8 1TQ, UK
| | - Thomas L Stubbs
- School of Life, Health and Chemical Sciences, Open University, Milton Keynes, MK7 6AE, UK
| | - Emily J Rayfield
- School of Earth Sciences, University of Bristol, Life Sciences Building, Tyndall Avenue, Bristol, BS8 1TQ, UK
| | - Michael J Benton
- School of Earth Sciences, University of Bristol, Life Sciences Building, Tyndall Avenue, Bristol, BS8 1TQ, UK
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5
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Laaß M, Kaestner A. Nasal turbinates of the dicynodont Kawingasaurus fossilis and the possible impact of the fossorial habitat on the evolution of endothermy. J Morphol 2023; 284:e21621. [PMID: 37585231 DOI: 10.1002/jmor.21621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2022] [Revised: 06/28/2023] [Accepted: 06/29/2023] [Indexed: 08/17/2023]
Abstract
The nasal region of the fossorial anomodont Kawingasaurus fossilis was virtually reconstructed from neutron-computed tomographic data and compared with the terrestrial species Pristerodon mackayi and other nonmammalian synapsids. The tomography of the Kawingasaurus skull reveals a pattern of maxillo-, naso-, fronto- and ethmoturbinal ridges that strongly resemble the mammalian condition. On both sides of the nasal cavity, remains of scrolled maxilloturbinals were preserved that were still partially articulated with maxilloturbinal ridges. Furthermore, possible remains of the lamina semicircularis as well as fronto- or ethmoturbinals were found. In Kawingasaurus, the maxilloturbinal ridges were longer and stronger than in Pristerodon. Except for the nasoturbinal ridges, no other ridges in the olfactory region and no remains of turbinates were recognized. This supports the hypothesis that naso-, fronto-, ethmo- and maxilloturbinals were a plesiomorphic feature of synapsids, but due to their cartilaginous nature in most taxa were, in almost all cases, not preserved. The well-developed maxilloturbinals in Kawingasaurus were probably an adaptation to hypoxia-induced hyperventilation in the fossorial habitat, maintaining the high oxygen demands of Kawingasaurus' large brain. The surface area of the respiratory turbinates in Kawingasaurus falls into the mammalian range, which suggests that they functioned as a countercurrent exchange system for thermoregulation and conditioning of the respiratory airflow. Our results suggest that the environmental conditions of the fossorial habitat led to specific sensory adaptations, accompanied by a pulse in brain evolution and of endothermy in cistecephalids, ~50 million years before the origin of endothermy in the mammalian stem line. This supports the Nocturnal Bottleneck Theory, in that we found evidence for a similar evolutionary scenario in cistecephalids as proposed for early mammals.
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Affiliation(s)
- Michael Laaß
- Fakultät für Geowissenschaften, Geotechnik und Bergbau, TU Bergakademie Freiberg, Freiberg, Germany
- FRM II and Physics E21, Technische Universität München, Garching, Germany
| | - Anders Kaestner
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, Villigen PSI, Switzerland
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6
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Bendel EM, Kammerer CF, Smith RMH, Fröbisch J. The postcranial anatomy of Gorgonops torvus (Synapsida, Gorgonopsia) from the late Permian of South Africa. PeerJ 2023; 11:e15378. [PMID: 37434869 PMCID: PMC10332358 DOI: 10.7717/peerj.15378] [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: 11/23/2022] [Accepted: 04/18/2023] [Indexed: 07/13/2023] Open
Abstract
Gorgonopsians are among the most recognizable groups of synapsids from the Permian period and have an extensive but mostly cranial fossil record. By contrast, relatively little is known about their postcranial anatomy. Here, we describe a nearly complete, semi-articulated skeleton of a gorgonopsian (identified as Gorgonops torvus) from the late Permian Endothiodon Assemblage Zone of the South African Karoo Basin and discuss its paleobiological implications. Known gorgonopsian postcrania indicate morphological conservatism in the group, but the skeletal anatomy of Gorgonops does differ from that of other gorgonopsians in some respects, such as in the triangular radiale and short terminal phalanges in the manus, and a weakly developed distinction between pubis and ischium in ventral aspect of the pelvic girdle. Similarities between the specimen described herein and a historically problematic specimen originally referred to "Scymnognathus cf. whaitsi" confirm referral of the latter specimen to Gorgonops. Since descriptions of gorgonopsian postcrania are rare, new interpretations of the lifestyle and ecology of Gorgonopsia can be drawn from our contribution. We conclude that gorgonopsians were likely ambush predators, able to chase their prey over short distances and pin them down with strong forelimbs before using their canines for the kill. This is evidenced by their different fore- and hindlimb morphology; the former stouter and more robust in comparison to the longer, more gracile, back legs. Furthermore, the completeness of the study specimen facilitates calculation of an estimated body mass of approximately 98 kg, similar to that of a modern lioness.
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Affiliation(s)
- Eva-Maria Bendel
- Institut für Biologie, Humboldt Universität zu Berlin, Berlin, Germany
- Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Berlin, Germany
| | - Christian F. Kammerer
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
- North Carolina Museum of Natural Sciences, Raleigh, North Carolina, United States of America
| | - Roger M. H. Smith
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
- Department of Karoo Palaeontology, Iziko South African Museum, Cape Town, South Africa
| | - Jörg Fröbisch
- Institut für Biologie, Humboldt Universität zu Berlin, Berlin, Germany
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
- Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Museum für Naturkunde, Berlin, Germany
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7
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Bazzana-Adams KD, Evans DC, Reisz RR. Neurosensory anatomy and function in Dimetrodon, the first terrestrial apex predator. iScience 2023; 26:106473. [PMID: 37096050 PMCID: PMC10122045 DOI: 10.1016/j.isci.2023.106473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 02/16/2023] [Accepted: 03/19/2023] [Indexed: 04/05/2023] Open
Abstract
Dimetrodon is among the most recognizable fossil taxa, as well as the earliest terrestrial amniote apex predator. The neuroanatomy and auditory abilities of Dimetrodon has long been the subject of interest, but palaeoneurological analyses have been limited by the lack of three-dimensional endocast data. The first virtual endocasts reveal a strongly flexed brain with enlarged floccular fossae and a surprisingly well-ossified bony labyrinth clearly preserving the semicircular canals, along with an undifferentiated vestibule and putative perilymphatic duct. This first detailed palaeoneurological reconstruction reveals potential adaptations for a predatory lifestyle and suggests Dimetrodon was able to hear a wider range of frequencies than anticipated, potentially being sensitive to frequencies equal to or higher than many extant sauropsids, despite lacking an impedance matching ear. Ancestral state reconstructions support the long-standing view of Dimetrodon as representative of the ancestral state for therapsids, while underscoring the importance of validating reconstructive analyses with fossil data.
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Bendel EM, Kammerer CF, Luo ZX, Smith RMH, Fröbisch J. The earliest segmental sternum in a Permian synapsid and its implications for the evolution of mammalian locomotion and ventilation. Sci Rep 2022; 12:13472. [PMID: 35931742 PMCID: PMC9356055 DOI: 10.1038/s41598-022-17492-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 07/26/2022] [Indexed: 11/30/2022] Open
Abstract
The sternum is a stabilizing element in the axial skeleton of most tetrapods, closely linked with the function of the pectoral girdle of the appendicular skeleton. Modern mammals have a distinctive sternum characterized by multiple ossified segments, the origins of which are poorly understood. Although the evolution of the pectoral girdle has been extensively studied in early members of the mammalian total group (Synapsida), only limited data exist for the sternum. Ancestrally, synapsids exhibit a single sternal element and previously the earliest report of a segmental sternum in non-mammalian synapsids was in the Middle Triassic cynodont Diademodon tetragonus. Here, we describe the well-preserved sternum of a gorgonopsian, a group of sabre-toothed synapsids from the Permian. It represents an ossified, multipartite element resembling the mammalian condition. This discovery pulls back the origin of the distinctive "mammalian" sternum to the base of Theriodontia, significantly extending the temporal range of this morphology. Through a review of sternal morphology across Synapsida, we reconstruct the evolutionary history of this structure. Furthermore, we explore its role in the evolution of mammalian posture, gait, and ventilation through progressive regionalization of the postcranium as well as the posteriorization of musculature associated with mammalian breathing.
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Affiliation(s)
- Eva-Maria Bendel
- Museum Für Naturkunde, Leibniz-Institut Für Evolutions- und Biodiversitätsforschung, Invalidenstraße 43, 10115, Berlin, Germany.
- Institut Für Biologie, Humboldt-Universität zu Berlin, Invalidenstraße 42, 10115, Berlin, Germany.
| | - Christian F Kammerer
- North Carolina Museum of Natural Sciences, 11 W Jones Street, Raleigh, NC, USA
- Evolutionary Studies Institute, University of the Witwatersrand, Yale Road, Johannesburg, 2000, South Africa
| | - Zhe-Xi Luo
- Department of Organismal Biology and Anatomy, University of Chicago, 1027 E 57th Street, Chicago, IL, USA
| | - Roger M H Smith
- Evolutionary Studies Institute, University of the Witwatersrand, Yale Road, Johannesburg, 2000, South Africa
- Department of Karoo Palaeontology, Iziko South African Museum, 25 Queen Victoria Street, Cape Town, 8001, South Africa
| | - Jörg Fröbisch
- Museum Für Naturkunde, Leibniz-Institut Für Evolutions- und Biodiversitätsforschung, Invalidenstraße 43, 10115, Berlin, Germany
- Institut Für Biologie, Humboldt-Universität zu Berlin, Invalidenstraße 42, 10115, Berlin, Germany
- Evolutionary Studies Institute, University of the Witwatersrand, Yale Road, Johannesburg, 2000, South Africa
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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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10
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Pusch LC, Kammerer CF, Fröbisch J. Cranial anatomy of Bolotridon frerensis, an enigmatic cynodont from the Middle Triassic of South Africa, and its phylogenetic significance. PeerJ 2021; 9:e11542. [PMID: 34178451 PMCID: PMC8214396 DOI: 10.7717/peerj.11542] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 05/10/2021] [Indexed: 01/17/2023] Open
Abstract
The cynodont fauna of the Trirachodon-Kannemeyeria Subzone of the Middle Triassic Cynognathus Assemblage Zone (AZ) is almost exclusively represented by taxa belonging to the clade Eucynodontia. However, there is one basal (non-eucynodont) cynodont known to have survived into this assemblage: the enigmatic Bolotridon frerensis. BSPG 1934-VIII-7 represents by far the most extensive specimen of B. frerensis, consisting of a partial skull with occluded lower jaw. The specimen was initially described by Broili & Schröder (1934), but their description was limited to surface details of the skull and the dental morphology. Here, by using a computed tomographic (CT) reconstruction, we redescribe this specimen, providing novel information on its palatal and internal anatomy. New endocranial characters recognized for this taxon include ridges in the nasal cavity indicating the presence of cartilaginous respiratory turbinals. New data obtained from the CT scan were incorporated into the most recently published data matrix of early non-mammalian cynodonts to test the previously unstable phylogenetic position of Bolotridon. Our phylogenetic analyses recovered Bolotridon as the sister-taxon of Eucynodontia, a more crownward position than previously hypothesized.
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Affiliation(s)
- Luisa C Pusch
- Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Berlin, Germany.,Institut für Biologie, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Christian F Kammerer
- North Carolina Museum of Natural Sciences, Raleigh, NC, USA.,Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
| | - Jörg Fröbisch
- Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Berlin, Germany.,Institut für Biologie, Humboldt-Universität zu Berlin, Berlin, Germany.,Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
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11
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Whitney MR, LeBlanc ARH, Reynolds AR, Brink KS. Convergent dental adaptations in the serrations of hypercarnivorous synapsids and dinosaurs. Biol Lett 2020; 16:20200750. [PMID: 33321067 DOI: 10.1098/rsbl.2020.0750] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Theropod dinosaurs are well known for having a ziphodont dentition: serrated, blade-shaped teeth that they used for cutting through prey. Serrations along the carinae of theropod teeth are composed of true denticles, a complex arrangement of dentine, enamel, and interdental folds. This structure would have supported individual denticles and dissipated the stresses associated with feeding. These particular serrations were previously thought to be unique to theropod dinosaurs and some other archosaurs. Here, we identify the same denticles and interdental folds forming the cutting edges in the teeth of a Permian gorgonopsian synapsid, extending the temporal and phylogenetic distribution of this dental morphology. This remarkable instance of convergence not only represents the earliest record of this adaptation to hypercarnivory but also demonstrates that the first iteration of this feature appeared in non-mammalian synapsids. Comparisons of tooth serrations in gorgonopsians with those of earlier synapsids and hypercarnivorous mammals reveal some gorgonopsians acquired a complex tissue arrangement that differed from other synapsids.
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Affiliation(s)
- M R Whitney
- Museum of Comparative Zoology, Harvard University, Cambridge, MA 02138, USA
| | - A R H LeBlanc
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9
| | - A R Reynolds
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada M5S 3B2
| | - K S Brink
- Department of Geological Sciences, University of Manitoba, 125 Dysart Road, Winnipeg, Manitoba, Canada R3T 2N2
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12
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Lautenschlager S, Figueirido B, Cashmore DD, Bendel EM, Stubbs TL. Morphological convergence obscures functional diversity in sabre-toothed carnivores. Proc Biol Sci 2020; 287:20201818. [PMID: 32993469 PMCID: PMC7542828 DOI: 10.1098/rspb.2020.1818] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Accepted: 09/08/2020] [Indexed: 11/12/2022] Open
Abstract
The acquisition of elongated, sabre-like canines in multiple vertebrate clades during the last 265 Myr represents a remarkable example for convergent evolution. Due to striking superficial similarities in the cranial skeleton, the same or similar skull and jaw functions have been inferred for sabre-toothed species and interpreted as an adaptation to subdue large-bodied prey. However, although some sabre-tooth lineages have been classified into different ecomorphs (dirk-tooths and scimitar-tooths) the functional diversity within and between groups and the evolutionary paths leading to these specializations are unknown. Here, we use a suite of biomechanical simulations to analyse key functional parameters (mandibular gape angle, bending strength, bite force) to compare the functional performance of different groups and to quantify evolutionary rates across sabre-tooth vertebrates. Our results demonstrate a remarkably high functional diversity between sabre-tooth lineages and that different cranial function and prey killing strategies evolved within clades. Moreover, different biomechanical adaptations in coexisting sabre-tooth species further suggest that this functional diversity was at least partially driven by niche partitioning.
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Affiliation(s)
- Stephan Lautenschlager
- School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Borja Figueirido
- Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga, 29071 Málaga, Spain
| | - Daniel D. Cashmore
- School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Eva-Maria Bendel
- Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstraße 43, 10115 Berlin, Germany
- Institut für Biologie, Humboldt-Universität zu Berlin, Invalidenstraße 42, 10115 Berlin, Germany
| | - Thomas L. Stubbs
- School of Earth Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
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13
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Brocklehurst N. Morphological evolution in therocephalians breaks the hypercarnivore ratchet. Proc Biol Sci 2020; 286:20190590. [PMID: 30966993 DOI: 10.1098/rspb.2019.0590] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Large carnivorous mammals have been suggested to show a ratchet-like mode of morphological evolution. A limited number of specializations for hypercarnivory evolve repeatedly in multiple clades, with those lineages evolving such specialities being unable to retreat back along their evolutionary trajectory or jump between adaptive peaks. While it has been hypothesized that such mechanisms should have applied to the evolution of other terrestrial carnivores, the non-mammalian synapsid clade Therocephalia appears to defy this expectation. The earliest, basalmost members of this clade are large macropredators, and it is later that small carnivores appear, seemingly evolving from top-predator ancestors. In order to test this reading of therocephalian evolution, variation in rates of body size evolution were tested for and incorporated into an ancestral reconstruction. Similar studies were made of the evolution of discrete characters related to carnivory. All analyses indicate the ancestral therocephalian was a large macro-predator, with serrated teeth, elongated canines and robust lower jaws. Small sizes apparently evolve later. It is therefore suggested that the hypercarnivore ratchet is a feature of mammalian evolution.
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Affiliation(s)
- Neil Brocklehurst
- Department of Earth Sciences, University of Oxford , 3 South Parks Road, Oxford OX1 3AN , UK
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14
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Pusch LC, Ponstein J, Kammerer CF, Fröbisch J. Novel Endocranial Data on the Early Therocephalian Lycosuchus vanderrieti Underpin High Character Variability in Early Theriodont Evolution. Front Ecol Evol 2020. [DOI: 10.3389/fevo.2019.00464] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
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15
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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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16
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Pavanatto AEB, Kerber L, Dias-da-Silva S. Virtual reconstruction of cranial endocasts of traversodontid cynodonts (Eucynodontia: Gomphodontia) from the upper Triassic of Southern Brazil. J Morphol 2019; 280:1267-1281. [PMID: 31241801 DOI: 10.1002/jmor.21029] [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] [Received: 04/04/2019] [Revised: 06/03/2019] [Accepted: 06/10/2019] [Indexed: 12/12/2022]
Abstract
The brain endocasts of the late Triassic (Carnian) traversodontids (Eucynodontia: Gomphodontia) Siriusgnathus niemeyerorum and Exaeretodon riograndensis from southern Brazil are described based on virtual models generated using computed tomography scan data. Their skull anatomy resembles that of other non-mammaliaform cynodonts, showing an endocranial cavity that is not fully ossified. A "V-shaped" orbitosphenoid, neither fully developed nor ossified is present in E. riograndensis. The nasal cavity is confluent with the encephalic cavity. Thus, the anterior limit of the olfactory bulbs is not definite. The brain endocast is elongated, being narrow anteriorly and wide posteriorly, with the maximum width at the parafloccular cast. The olfactory bulbs do not present a clear division between their counterparts, due to the absence of a longitudinal sulcus. A longitudinal sulcus in the forebrain delimiting the cerebral hemispheres, the pineal tube, and the parietal foramen are absent in both taxa. The large and well-developed unossified zone is partially separated from the remaining endocast by a notch formed by the supraoccipital. The encephalization quotients, as well as the endocranial volume/body mass relationships of S. niemeyerorum and E. riograndensis are within the range expected for non-mammaliaform Therapsida.
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Affiliation(s)
- Ane E B Pavanatto
- Programa de Pós-Graduação em Biodiversidade Animal, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, Brazil
| | - Leonardo Kerber
- Programa de Pós-Graduação em Biodiversidade Animal, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, Brazil.,Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, São João do Polêsine, Brazil
| | - Sérgio Dias-da-Silva
- Programa de Pós-Graduação em Biodiversidade Animal, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, Brazil.,Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, São João do Polêsine, Brazil
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Benoit J, Ruf I, Miyamae JA, Fernandez V, Rodrigues PG, Rubidge BS. The Evolution of the Maxillary Canal in Probainognathia (Cynodontia, Synapsida): Reassessment of the Homology of the Infraorbital Foramen in Mammalian Ancestors. J MAMM EVOL 2019. [DOI: 10.1007/s10914-019-09467-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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