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Rabe C, Marugán-Lobón J, Smith RMH, Chinsamy A. Geometric morphometric analysis of an ontogenetic cranial series of the Permian dicynodont Diictodon feliceps. Proc Biol Sci 2024; 291:20240626. [PMID: 39081192 PMCID: PMC11289659 DOI: 10.1098/rspb.2024.0626] [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: 07/07/2023] [Revised: 05/27/2024] [Accepted: 05/28/2024] [Indexed: 08/02/2024] Open
Abstract
The Karoo Basin of South Africa is renowned for its abundance and diversity of therapsid fossils. Among the most ubiquitous and persistent of the Permian fauna is the small herbivorous dicynodont Diictodon feliceps. Intraspecific variation in Diictodon is historically confounding, and while ontogeny is frequently cited as a potential source of variation, observable developmental changes have never been calibrated. The present study revisits this issue, comparing three-dimensional landmark configurations of 82 Diictodon crania to investigate the association between shape, size and dimorphism. Beyond the statistically significant relationship between shape and allometry, our results determine the shape differences between juvenile and adult skulls of Diictodon, aligned with common craniofacial features documented in other tetrapod taxa. Functionally, these changes are attributed to development of the jaw musculature for feeding on larger, tougher plant matter during later ontogeny. Cranial morphological variation owing to sexual dimorphism is negligible, but distinct differences are noted in the allometric trajectories of each morphotype. A component of non-allometric variation cannot be accounted for, and we propose that this represents natural variation, rather than an artefact of taphonomic deformation.
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Affiliation(s)
- Caitlin Rabe
- Department of Biological Sciences, University of Cape Town, Cape Town7700, South Africa
| | | | - Roger M. H. Smith
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
- Karoo Palaeontology, Iziko South African Museum, Cape Town7700, South Africa
| | - Anusuya Chinsamy
- Department of Biological Sciences, University of Cape Town, Cape Town7700, South Africa
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2
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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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3
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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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4
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Lund ES, Norton LA, Benoit J. First CT-assisted study of the palate and postcrania of Diarthrognathus broomi (Cynodontia, Probainognathia). Anat Rec (Hoboken) 2024; 307:1538-1558. [PMID: 38131650 DOI: 10.1002/ar.25363] [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: 07/28/2023] [Revised: 11/19/2023] [Accepted: 11/21/2023] [Indexed: 12/23/2023]
Abstract
Diarthrognathus broomi is a transitional taxon between non-mammaliaform cynodonts and Mammaliaformes that occurred during the Late Triassic to Early Jurassic. All known specimens of Diarthrognathus represent juveniles, and the postcrania have not been thoroughly described. The palatal, basicranial and postcranial elements of the referred specimen NMQR 1535 are described here for the first time using 3D reconstructions generated from X-ray micro-computed tomography (μCT) data. The presence of a large interpterygoid vacuity, open medial suture between the vomers and medially unossified secondary palate all support the interpretation that NMQR 1535 is a juvenile. In addition, Diarthrognathus uniquely possesses "suborbital" vacuities, which distinguishes it from every other known cynodont. The presence of an ossified olecranon process, among other features, suggests that Diarthrognathus may have been a scratch-digger. The postcranial skeleton of Diarthrognathus appears to be more plesiomorphic than tritylodontids, Brasilodon and other tritheledontids as, among other traits, it retains amphicoelous vertebrae. However, this taxon also displays synapomorphies with the more derived cynodonts, such as the mammalian pattern of neurocentral ossification and possible absence of an ectepicondylar foramen.
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Affiliation(s)
- Erin S Lund
- Evolutionary Studies Institute (ESI), School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Luke A Norton
- Evolutionary Studies Institute (ESI), School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Julien Benoit
- Evolutionary Studies Institute (ESI), School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
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5
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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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6
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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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7
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Abdala F, Norton LA, Jasinoski SC, Botha J, Fernandez V, Rubidge B, Gill PG, Martinelli AG. On taxonomic issues, ontogenetic series and tooth replacement. Comments on Diphyodont tooth replacement of Brasilodon-A late Triassic eucynodont that challenges the time of origin of mammals by Cabreira et al. J Anat 2023; 242:737-742. [PMID: 36715111 PMCID: PMC10008281 DOI: 10.1111/joa.13803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Accepted: 11/23/2022] [Indexed: 01/31/2023] Open
Affiliation(s)
- Fernando Abdala
- Unidad Ejecutora Lillo (CONICET-Fundación Miguel Lillo), Tucumán, Argentina.,Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
| | - Luke A Norton
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
| | - Sandra C Jasinoski
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
| | - Jennifer Botha
- National Museum, Bloemfontein, South Africa.,Department of Zoology and Entomology, University of the Free State, Bloemfontein, South Africa
| | - Vincent Fernandez
- European Synchrotron Radiation Facility, Structure of Materials Department, Grenoble, France
| | - Bruce Rubidge
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
| | - Pamela G Gill
- School of Earth Sciences, University of Bristol, Bristol, UK.,Department of Earth Sciences, Natural History Museum London, London, UK
| | - Agustín G Martinelli
- Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"-Consejo Nacional de Investigaciones Científicas y Técnicas (MACN-CONICET), Ciudad Autónoma de Buenos Aires, Argentina
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8
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A complete skull of a stem mammal from the Late Triassic of Brazil illuminates the early evolution of prozostrodontian cynodonts. J MAMM EVOL 2023. [DOI: 10.1007/s10914-022-09648-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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9
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Rayner RR, Butler RJ, Kammerer CF, Choiniere JN. Guttigomphus avilionis gen. et sp. nov., a trirachodontid cynodont from the upper Cynognathus Assemblage Zone, Burgersdorp Formation of South Africa. PeerJ 2022; 10:e14355. [PMID: 36545384 PMCID: PMC9762250 DOI: 10.7717/peerj.14355] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Accepted: 10/17/2022] [Indexed: 12/23/2022] Open
Abstract
The Burgersdorp Formation of South Africa is a richly fossiliferous rock sequence at the top of the Permian-Triassic Beaufort Group and is known for its abundance of Early-Middle Triassic vertebrate remains, particularly cynodonts. Fossils from the Burgersdorp Formation are referred biostratigraphically to the Cynognathus Assemblage Zone (CAZ), which is further divided into three subzones: Langbergia-Garjainia, Trirachodon-Kannemeyeria, and Cricodon-Ufudocyclops. Each subzone is characterised by the presence of a distinct species of trirachodontid, a group of gomphodont cynodonts found relatively abundantly throughout the CAZ, with the lower two subzones characterised by the medium-sized trirachodontids Langbergia and Trirachodon. The uppermost part of the formation, the Cricodon-Ufudocyclops subzone, yields trirachodontids of larger size. The majority of these trirachodontid specimens have previously been referred to Cricodon metabolus, a taxon also known from the Manda Beds of Tanzania and the Ntawere Formation of Zambia. Here we identify one of the specimens (BP/1/5538) previously referred to Cricodon as a new taxon, Guttigomphus avilionis. Guttigomphus can be distinguished from other gomphodont cynodonts by features of the upper postcanine teeth, such as an asymmetric crown in occlusal view (crown narrower along the lingual margin than the labial). Our phylogenetic analysis recovers Guttigomphus as a basal member of Trirachodontidae, outside of the clade including Cricodon, Langbergia and Trirachodon.
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Affiliation(s)
- Romy R. Rayner
- School of Geography, Earth & Environmental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Richard J. Butler
- School of Geography, Earth & Environmental Sciences, University of Birmingham, Birmingham, United Kingdom,Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
| | - 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
| | - Jonah N. Choiniere
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
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10
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Wynd B, Abdala F, Nesbitt SJ. Ontogenetic growth in the crania of Exaeretodon argentinus (Synapsida: Cynodontia) captures a dietary shift. PeerJ 2022; 10:e14196. [PMID: 36299507 PMCID: PMC9590418 DOI: 10.7717/peerj.14196] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 09/15/2022] [Indexed: 01/26/2023] Open
Abstract
Background An ontogenetic niche shift in vertebrates is a common occurrence where ecology shifts with morphological changes throughout growth. How ecology shifts over a vertebrate's lifetime is often reconstructed in extant species-by combining observational and skeletal data from growth series of the same species-because interactions between organisms and their environment can be observed directly. However, reconstructing shifts using extinct vertebrates is difficult and requires well-sampled growth series, specimens with relatively complete preservation, and easily observable skeletal traits associated with ecologies suspected to change throughout growth, such as diet. Methods To reconstruct ecological changes throughout the growth of a stem-mammal, we describe changes associated with dietary ecology in a growth series of crania of the large-bodied (∼2 m in length) and herbivorous form, Exaeretodon argentinus (Cynodontia: Traversodontidae) from the Late Triassic Ischigualasto Formation, San Juan, Argentina. Nearly all specimens were deformed by taphonomic processes, so we reconstructed allometric slope using a generalized linear mixed effects model with distortion as a random effect. Results Under a mixed effects model, we find that throughout growth, E. argentinus reduced the relative length of the palate, postcanine series, orbits, and basicranium, and expanded the relative length of the temporal region and the height of the zygomatic arch. The allometric relationship between the zygomatic arch and temporal region with the total length of the skull approximate the rate of growth for feeding musculature. Based on a higher allometric slope, the zygoma height is growing relatively faster than the length of the temporal region. The higher rate of change in the zygoma may suggest that smaller individuals had a crushing-dominated feeding style that transitioned into a chewing-dominated feeding style in larger individuals, suggesting a dietary shift from possible faunivory to a more plant-dominated diet. Dietary differentiation throughout development is further supported by an increase in sutural complexity and a shift in the orientation of microwear anisotropy between small and large individuals of E. argentinus. A developmental transition in the feeding ecology of E. argentinus is reflective of the reconstructed dietary transition across Gomphodontia, wherein the earliest-diverging species are inferred as omnivorous and the well-nested traversodontids are inferred as herbivorous, potentially suggesting that faunivory in immature individuals of the herbivorous Traversodontidae may be plesiomorphic for the clade.
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Affiliation(s)
- Brenen Wynd
- Department of Geosciences, Virginia Tech, Blacksburg, VA, United States of America
| | - Fernando Abdala
- CONICET-Fundación Miguel Lillo, Unidad Ejecutora Lillo, San Miguel de Tucumán, Tucumán, Argentina
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
| | - Sterling J. Nesbitt
- Department of Geosciences, Virginia Tech, Blacksburg, VA, United States of America
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11
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Duhamel A, Benoit J, Day M, Rubidge B, Fernandez V. Computed Tomography elucidates ontogeny within the basal therapsid clade Biarmosuchia. PeerJ 2021; 9:e11866. [PMID: 34527434 PMCID: PMC8403480 DOI: 10.7717/peerj.11866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Accepted: 07/05/2021] [Indexed: 11/20/2022] Open
Abstract
Biarmosuchia is a clade of basal therapsids that includes forms possessing plesiomorphic ‘pelycosaurian’ cranial characters as well as the highly derived Burnetiamorpha which are characterised by cranial pachyostosis and a variety of cranial bosses. Potential ontogenetic variation in these structures has been suggested based on growth series of other therapsids with pachyostosed crania, which complicates burnetiamorph taxonomic distinction and thus it is essential to better understand cranial ontogeny of the Burnetiamorpha. Here, three new juvenile biarmosuchian skulls from the late Permian of South Africa are described using X-ray micro computed tomography (CT). We found that juvenile biarmosuchians are distinguished from adults by their relatively large orbits, open cranial sutures, and incomplete ossification of the braincase and bony labyrinth. Also, they manifest multiple centres of ossification within the parietal and preparietal bones. CT examination reveals that the holotype of Lemurosaurus pricei (BP/1/816), previously alleged to be a juvenile, shows no evidence of juvenility and is thus probably an adult. This suggests that the larger skull NMQR 1702, previously considered to be an adult L. pricei, may represent a new taxon. This study provides, for the first time, a list of characters by which to recognise juvenile biarmosuchians.
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Affiliation(s)
- Aliénor Duhamel
- ENS de Lyon, CNRS, UMR 5276, LGL-TPE, Université Claude Bernard (Lyon I), Lyon, France.,Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa.,School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Julien Benoit
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa.,School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Michael Day
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa.,Department of Earth Sciences, Natural History Museum, London, United Kingdom
| | - Bruce Rubidge
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa.,School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Vincent Fernandez
- Department of Earth Sciences, Natural History Museum, London, United Kingdom.,European Synchrotron Radiation Facility, Grenoble, France
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12
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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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13
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Wynd BM, Uyeda JC, Nesbitt SJ. Including Distorted Specimens in Allometric Studies: Linear Mixed Models Account for Deformation. Integr Org Biol 2021; 3:obab017. [PMID: 34377943 PMCID: PMC8341891 DOI: 10.1093/iob/obab017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Allometry—patterns of relative change in body parts—is a staple for examining how clades exhibit scaling patterns representative of evolutionary constraint on phenotype, or quantifying patterns of ontogenetic growth within a species. Reconstructing allometries from ontogenetic series is one of the few methods available to reconstruct growth in fossil specimens. However, many fossil specimens are deformed (twisted, flattened, and displaced bones) during fossilization, changing their original morphology in unpredictable and sometimes undecipherable ways. To mitigate against post burial changes, paleontologists typically remove clearly distorted measurements from analyses. However, this can potentially remove evidence of individual variation and limits the number of samples amenable to study, which can negatively impact allometric reconstructions. Ordinary least squares (OLS) regression and major axis regression are common methods for estimating allometry, but they assume constant levels of residual variation across specimens, which is unlikely to be true when including both distorted and undistorted specimens. Alternatively, a generalized linear mixed model (GLMM) can attribute additional variation in a model (e.g., fixed or random effects). We performed a simulation study based on an empirical analysis of the extinct cynodont, Exaeretodon argentinus, to test the efficacy of a GLMM on allometric data. We found that GLMMs estimate the allometry using a full dataset better than simply using only non-distorted data. We apply our approach on two empirical datasets, cranial measurements of actual specimens of E. argentinus (n = 16) and femoral measurements of the dinosaur Tawa hallae (n = 26). Taken together, our study suggests that a GLMM is better able to reconstruct patterns of allometry over an OLS in datasets comprised of extinct forms and should be standard protocol for anyone using distorted specimens.
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Affiliation(s)
- B M Wynd
- Department of Geosciences, Virginia Tech, Blacksburg, VA 24061, USA
| | - J C Uyeda
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, USA
| | - S J Nesbitt
- Department of Geosciences, Virginia Tech, Blacksburg, VA 24061, USA
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14
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Norton LA, Abdala F, Rubidge BS, Botha J. Tooth replacement patterns in the Early Triassic epicynodont Galesaurus planiceps (Therapsida, Cynodontia). PLoS One 2020; 15:e0243985. [PMID: 33378326 PMCID: PMC7773207 DOI: 10.1371/journal.pone.0243985] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Accepted: 12/02/2020] [Indexed: 01/13/2023] Open
Abstract
Sixteen specimens of the Early Triassic cynodont Galesaurus planiceps (including eight that were scanned using micro-computed tomography) representing different ontogenetic stages were assembled to study the dental replacement in the species. The growth series shows that the incisors and postcanines continue to develop and replace, even in the largest (presumably oldest) specimen. In contrast, replacement of the canines ceased with the attainment of skeletal maturity, at a basal skull length of ~90 mm, suggesting that Galesaurus had a finite number of canine replacement cycles. Additionally, the functional canine root morphology of these larger specimens showed a tendency to be open-rooted, a condition not previously reported in Mesozoic theriodonts. An alternating pattern of tooth replacement was documented in the maxillary and mandibular postcanine series. Both postcanine series increased in tooth number as the skull lengthened, with the mandibular postcanine series containing more teeth than the maxillary series. In the maxilla, the first postcanine is consistently the smallest tooth, showing a proportional reduction in size as skull length increased. The longer retention of a tooth in this first locus is a key difference between Galesaurus and Thrinaxodon, in which the mesial-most postcanines are lost after replacement. This difference has contributed to the lengthening of the postcanine series in Galesaurus, as teeth continued to be added to the distal end of the tooth row through ontogeny. Overall, there are considerable differences between Galesaurus and Thrinaxodon relating to the replacement and development of their teeth.
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Affiliation(s)
- Luke A. Norton
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, Gauteng, South Africa
- School of Geosciences, University of the Witwatersrand, Johannesburg, Gauteng, South Africa
- * E-mail:
| | - Fernando Abdala
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, Gauteng, South Africa
- Unidad Ejecutora Lillo (CONICET-Fundación Miguel Lillo), Tucumán, Argentina
| | - Bruce S. Rubidge
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, Gauteng, South Africa
- School of Geosciences, University of the Witwatersrand, Johannesburg, Gauteng, South Africa
| | - Jennifer Botha
- Karoo Palaeontology, National Museum, Bloemfontein, Free State, South Africa
- Department of Zoology and Entomology, University of the Free State, Bloemfontein, Free State, South Africa
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15
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Kligman BT, Marsh AD, Sues HD, Sidor CA. A new non-mammalian eucynodont from the Chinle Formation (Triassic: Norian), and implications for the early Mesozoic equatorial cynodont record. Biol Lett 2020; 16:20200631. [PMID: 33142088 PMCID: PMC7728676 DOI: 10.1098/rsbl.2020.0631] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Accepted: 10/12/2020] [Indexed: 11/12/2022] Open
Abstract
The Upper Triassic tetrapod fossil record of North America features a pronounced discrepancy between the assemblages of present-day Virginia and North Carolina relative to those of the American Southwest. While both are typified by large-bodied archosaurian reptiles like phytosaurs and aetosaurs, the latter notably lacks substantial representation of mammal relatives, including cynodonts. Recently collected non-mammalian eucynodontian jaws from the middle Norian Blue Mesa Member of the Chinle Formation in northeastern Arizona shed light on the Triassic cynodont record from western equatorial Pangaea. Importantly, they reveal new biogeographic connections to eastern equatorial Pangaea as well as southern portions of the supercontinent. This discovery indicates that the faunal dissimilarity previously recognized between the western and eastern portions of equatorial Pangaea is overstated and possibly reflects longstanding sampling biases, rather than a true biogeographic pattern.
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Affiliation(s)
- Ben T. Kligman
- Department of Geosciences, Virginia Tech, Blacksburg, VA 24061, USA
- Petrified Forest National Park, 1 Park Road, Petrified Forest, AZ 86028, USA
| | - Adam D. Marsh
- Petrified Forest National Park, 1 Park Road, Petrified Forest, AZ 86028, USA
| | - Hans-Dieter Sues
- Department of Paleobiology, National Museum of Natural History, MRC 121, PO Box 37012, Washington, DC 20013-7012, USA
| | - Christian A. Sidor
- Department of Biology and Burke Museum, University of Washington, Seattle, WA 98195-1800, USA
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16
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Liu J, Abdala F. The tetrapod fauna of the upper Permian Naobaogou Formation of China: 5. Caodeyao liuyufengi gen. et sp. nov., a new peculiar therocephalian. PeerJ 2020; 8:e9160. [PMID: 32523808 PMCID: PMC7261480 DOI: 10.7717/peerj.9160] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 04/18/2020] [Indexed: 11/20/2022] Open
Abstract
The upper Permian Naobaogou Formation has been the goal of recent contributions that notably increased the knowledge of its terrestrial vertebrate fauna and unravelled a hidden late Permian therocephalian diversity in China. Two very different species of therocephalians have been documented in the Naobaogou Formation and they were recovered as basal akidnognathids in cladistic analyses. In this contribution we describe Caodeyao liuyufengi gen. et sp. nov., represented by a partial skull and mandible, and a humerus. The new taxon features a short, high snout and a wide temporal opening with the coronoid process of the mandible separated by a wide space medially to the zygomatic arch. The latter feature is only recognized in the Russian therocephalian Purlovia maxima and it is also characteristic of non-mammaliaform cynodonts. Phylogenetic analysis indicates a close relationship of the new Chinese taxon with Purlovia maxima, producing a monophyletic Laurasian group in therocephalian phylogeny. With the representation of three different species, the Naobaogou Formation is now the most prolific unit documenting therocephalian late Permian diversity in China.
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Affiliation(s)
- Jun Liu
- Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China.,College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China.,CAS Center for Excellence in Life and Paleoenvironment, Beijing, China
| | - Fernando Abdala
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa.,Unidad Ejecutora Lillo (CONICET-Fundación Miguel Lillo), Tucuman, Argentina
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17
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Zhou CF, Bhullar BAS, Neander AI, Martin T, Luo ZX. New Jurassic mammaliaform sheds light on early evolution of mammal-like hyoid bones. Science 2019; 365:276-279. [DOI: 10.1126/science.aau9345] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2018] [Accepted: 06/12/2019] [Indexed: 12/15/2022]
Affiliation(s)
- Chang-Fu Zhou
- Paleontological Museum of Liaoning, Shenyang Normal University, Shenyang Liaoning 110034, China
- College of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao, Shandong 266590, China
| | - Bhart-Anjan S. Bhullar
- Department of Geology and Geophysics and Peabody Museum of Natural History, Yale University, New Haven, CT 06511, USA
| | - April I. Neander
- Department of Organismal Biology and Anatomy, The University of Chicago, Chicago, IL 60637, USA
| | - Thomas Martin
- Section Paleontology, Institute of Geosciences, Rheinische Friedrich-Wilhelms-Universität Bonn, 53115 Bonn, Germany
| | - Zhe-Xi Luo
- Department of Organismal Biology and Anatomy, The University of Chicago, Chicago, IL 60637, USA
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18
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Abdala F, Gaetano LC, Smith RMH, Rubidge BS. A new large cynodont from the Late Permian (Lopingian) of the South African Karoo Basin and its phylogenetic significance. Zool J Linn Soc 2019. [DOI: 10.1093/zoolinnean/zlz004] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Abstract
The Karoo Basin of South Africa has the best global record of Lopingian (Late Permian) non-mammaliaform cynodonts, currently represented by five species. We describe Vetusodon elikhulu gen. et sp. nov., documented by four specimens from the Daptocephalus Assemblage Zone. With a basal skull length of ~18 cm, it is the largest Lopingian cynodont and is also larger than Induan representatives of the group. Vetusodon elikhulu has a cranial morphology that departs notably from that previously documented for Permo-Triassic cynodonts. It features a short and extremely wide snout, resembling that of the contemporaneous therocephalian Moschorhinus, and has large incisors and canines that contrast with the small unicusped postcanines, suggesting a more important role of the anterior dentition for feeding. The dentary is extremely long and robust, with the posterior margin located closer to the craniomandibular joint than in other Lopingian and Induan cynodonts (e.g. Thrinaxodon). The secondary palate morphology of V. elikhulu is unique, being short and incomplete and with the posterior portion of the maxilla partly covering the vomer. A phylogenetic analysis suggests that V. elikhulu is the sister taxon of Eucynodontia and thus the most derived of the Lopingian to Induan cynodonts yet discovered.
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Affiliation(s)
- Fernando Abdala
- Unidad Ejecutora Lillo, Conicet-Fundación Miguel Lillo, Tucumán, Argentina
- Evolutionary Studies Institute and School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Leandro C Gaetano
- Evolutionary Studies Institute and School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
- Departamento de Ciencias Geológicas, Facultad de Ciencias Exactas y Naturales, Instituto de Estudios Andinos ‘Don Pablo Groeber’, IDEAN (Universidad de Buenos Aires, CONICET), Intendente Güiraldes, Ciudad Universitaria – Pabellón II, C1428EGA, Ciudad Autónoma de Buenos Aires, Argentina
| | - Roger M H Smith
- Evolutionary Studies Institute and School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
- Department of Karoo Palaeontology, Iziko South African Museum, Cape Town, South Africa
| | - Bruce S Rubidge
- Evolutionary Studies Institute and School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
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19
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Pusch LC, Kammerer CF, Fröbisch J. Cranial anatomy of the early cynodont Galesaurus planiceps and the origin of mammalian endocranial characters. J Anat 2019; 234:592-621. [PMID: 30772942 DOI: 10.1111/joa.12958] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/16/2019] [Indexed: 12/19/2022] Open
Abstract
The cranial anatomy of the early non-mammalian cynodont Galesaurus planiceps from the South African Karoo Basin is redescribed on the basis of a computed tomographic reconstruction of the skull. Previously, little was known about internal skull morphology and the nervous and sensory system of this taxon. The endocranial anatomy of various cynodonts has been intensively studied in recent years to understand the origin of mammalian characters in the nasal capsule, brain and ear. However, these studies have focused on only a few taxa, the earliest of which is another Early Triassic cynodont, Thrinaxodon liorhinus. Galesaurus is phylogenetically stemward of Thrinaxodon and thus provides a useful test of whether the mammal-like features observed in Thrinaxodon were present even more basally in cynodont evolution. The cranial anatomy of G. planiceps is characterized by an intriguing mosaic of primitive and derived features within cynodonts. In contrast to the very similar internal nasal and braincase morphology of Galesaurus and Thrinaxodon, parts of the skull that seem to be fairly conservative in non-prozostrodont cynodonts, the morphology of the maxillary canal differs markedly between these taxa. Unusually, the maxillary canal of Galesaurus has relatively few ramifications, more similar to those of probainognathian cynodonts than that of Thrinaxodon. However, its caudal section is very short, a primitive feature shared with gorgonopsians and therocephalians. The otic labyrinth of Galesaurus is generally similar to that of Thrinaxodon, but differs in some notable features (e.g. proportional size of the anterior semicircular canal). An extremely large, protruding paraflocculus of the brain and a distinct medioventrally located notch on the anterior surface of the tabular, which forms the dorsal border of the large parafloccular lobe, are unique to Galesaurus among therapsids with reconstructed endocasts. These features may represent autapomorphies of Galesaurus, but additional sampling is needed at the base of Cynodontia to test this.
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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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20
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LeBlanc ARH, Brink KS, Whitney MR, Abdala F, Reisz RR. Dental ontogeny in extinct synapsids reveals a complex evolutionary history of the mammalian tooth attachment system. Proc Biol Sci 2018; 285:20181792. [PMID: 30404877 PMCID: PMC6235047 DOI: 10.1098/rspb.2018.1792] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Accepted: 10/12/2018] [Indexed: 12/23/2022] Open
Abstract
The mammalian dentition is uniquely characterized by a combination of precise occlusion, permanent adult teeth and a unique tooth attachment system. Unlike the ankylosed teeth in most reptiles, mammal teeth are supported by a ligamentous tissue that suspends each tooth in its socket, providing flexible and compliant tooth attachment that prolongs the life of each tooth and maintains occlusal relationships. Here we investigate dental ontogeny through histological examination of a wide range of extinct synapsid lineages to assess whether the ligamentous tooth attachment system is unique to mammals and to determine how it evolved. This study shows for the first time that the ligamentous tooth attachment system is not unique to crown mammals within Synapsida, having arisen in several non-mammalian therapsid clades as a result of neoteny and progenesis in dental ontogeny. Mammalian tooth attachment is here re-interpreted as a paedomorphic condition relative to the ancestral synapsid form of tooth attachment.
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Affiliation(s)
- Aaron R H LeBlanc
- Department of Biology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, Ontario, Canada L5L 1C6
- Department of Biological Sciences, Faculty of Science, University of Alberta, Edmonton, Alberta, Canada T6G 2E9
| | - Kirstin S Brink
- Department of Biology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, Ontario, Canada L5L 1C6
- Department of Oral Health Sciences, Faculty of Dentistry, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Megan R Whitney
- Department of Biology and Burke Museum, University of Washington, Seattle, WA, USA
| | - Fernando Abdala
- Unidad Ejecutora Lillo, Conicet, Tucumán, Argentina
- Evolutionary Studies Institute and School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
- National Research Foundation, Centre of Excellence: Palaeosciences, Pretoria, South Africa
| | - Robert R Reisz
- Department of Biology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, Ontario, Canada L5L 1C6
- Institute of Oral Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan, Republic of China
- DERC, Jilin University, Changchun, Jilin Province, People's Republic of China
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21
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Hoffman EA, Rowe TB. Jurassic stem-mammal perinates and the origin of mammalian reproduction and growth. Nature 2018; 561:104-108. [DOI: 10.1038/s41586-018-0441-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Accepted: 07/17/2018] [Indexed: 12/16/2022]
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22
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Grieco TM, Richman JM. Coordination of bilateral tooth replacement in the juvenile gecko is continuous with in ovo patterning. Evol Dev 2018; 20:51-64. [PMID: 29318754 PMCID: PMC5834371 DOI: 10.1111/ede.12247] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We performed a test of how function impacts a genetically programmed process that continues into postnatal life. Using the dentition of the polyphyodont gecko as our model, tooth shedding was recorded longitudinally across the jaw. We compared two time periods: one in which teeth were patterned symmetrically in ovo and a later period when teeth were initiated post-hatching. By pairing shedding events on the right and left sides, we found the patterns of tooth loss are symmetrical and stable between periods, with only subtle deviations. Contralateral tooth positions shed within 3-4 days of each other in most animals (7/10). A minority of animals (3/10) had systematic tooth position shifts between right and left sides, likely due to changes in functional tooth number. Our results suggest that in addition to reproducible organogenesis of individual teeth, there is also a neotenic retention of jaw-wide dental patterning in reptiles. Finer analysis of regional asymmetries revealed changes to which contralateral position shed first, affecting up to one quarter of the jaw (10 tooth positions). Once established, these patterns were retained longitudinally. Taken together, the data support regional and global mechanisms of coordinating tooth cycling post-hatching.
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Affiliation(s)
- Theresa M Grieco
- Department of Oral Health Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Joy M Richman
- Department of Oral Health Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
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23
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Benoit J, Jasinoski SC, Fernandez V, Abdala F. The mystery of a missing bone: revealing the orbitosphenoid in basal Epicynodontia (Cynodontia, Therapsida) through computed tomography. THE SCIENCE OF NATURE - NATURWISSENSCHAFTEN 2017; 104:66. [PMID: 28721557 DOI: 10.1007/s00114-017-1487-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 04/12/2017] [Accepted: 06/29/2017] [Indexed: 11/26/2022]
Abstract
The basal non-mammaliaform cynodonts from the late Permian (Lopingian) and Early Triassic are a major source of information for the understanding of the evolutionary origin of mammals. Detailed knowledge of their anatomy is critical for understanding the phylogenetic transition toward mammalness and the paleobiological reconstruction of mammalian precursors. Using micro-computed tomography (μCT), we describe the internal morphology of the interorbital region that includes the rarely fossilized orbitosphenoid elements in four basal cynodonts. These paired bones, which are positioned relatively dorsally in the skull, contribute to the wall of the anterior part of the braincase and form the floor for the olfactory lobes. Unlike procynosuchids and the more basal therapsids in which the orbitosphenoids are well developed, dense, and bear a ventral keel, the basal epicynodonts Cynosaurus, Galesaurus, and Thrinaxodon display cancellous, reduced, and loosely articulated orbitosphenoids, a condition shared with many eucynodonts. The hemi-cylindrical orbitosphenoid from which the mammalian condition is derived re-evolved convergently in traversodontid and some probainognathian cynodonts.
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Affiliation(s)
- Julien Benoit
- Evolutionary Studies Institute; School of Geosciences, University of the Witwatersrand, Private Bag 3, WITS, Johannesburg, 2050, South Africa.
- School of Anatomical Sciences, University of the Witwatersrand, 7 York Road, Johannesburg, 2193, South Africa.
| | - Sandra C Jasinoski
- Evolutionary Studies Institute; School of Geosciences, University of the Witwatersrand, Private Bag 3, WITS, Johannesburg, 2050, South Africa
| | - Vincent Fernandez
- European Synchrotron Radiation Facility, 71 rue des Martyrs, 38000, Grenoble, France
| | - Fernando Abdala
- Evolutionary Studies Institute; School of Geosciences, University of the Witwatersrand, Private Bag 3, WITS, Johannesburg, 2050, South Africa
- Unidad Ejecutora Lillo CONICET, Miguel Lillo, 251, Tucumán, Argentina
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24
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Jasinoski SC, Abdala F. Aggregations and parental care in the Early Triassic basal cynodonts Galesaurus planiceps and Thrinaxodon liorhinus. PeerJ 2017; 5:e2875. [PMID: 28097072 PMCID: PMC5228509 DOI: 10.7717/peerj.2875] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Accepted: 12/06/2016] [Indexed: 12/01/2022] Open
Abstract
Non-mammaliaform cynodonts gave rise to mammals but the reproductive biology of this extinct group is still poorly known. Two exceptional fossils of Galesaurus planiceps and Thrinaxodon liorhinus, consisting of juveniles closely associated with an adult, were briefly described more than 50 years ago as examples of parental care in non-mammaliaform cynodonts. However, these two Early Triassic fossils have largely been excluded from recent discussions of parental care in the fossil record. Here we re-analyse these fossils in the context of an extensive survey of other aggregations found in these two basal cynodont taxa. Our analysis revealed six other unequivocal cases of aggregations in Thrinaxodon, with examples of same-age aggregations among immature or adult individuals as well as mixed-age aggregations between subadult and adult individuals. In contrast, only one additional aggregation of Galesauruswas identified. Taking this comprehensive survey into account, the two previously described cases of parental care in Galesaurus and Thrinaxodon are substantiated. The juveniles are the smallest specimens known for each taxon, and the size difference between the adult and the two associated juveniles is the largest found for any of the aggregations. The juveniles of Thrinaxodon are approximately only 37% of the associated adult size; whereas in Galesaurus, the young are at least 60% of the associated adult size. In each case, the two juvenile individuals are similar in size, suggesting they were from the same clutch. Even though parental care was present in both Galesaurus and Thrinaxodon, intraspecific aggregations were much more common in Thrinaxodon, suggesting it regularly lived in aggregations consisting of both similar and different aged individuals.
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Affiliation(s)
- Sandra C Jasinoski
- Evolutionary Studies Institute, University of the Witwatersrand , Johannesburg , South Africa
| | - Fernando Abdala
- Evolutionary Studies Institute, University of the Witwatersrand , Johannesburg , South Africa
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25
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Lautenschlager S, Gill P, Luo ZX, Fagan MJ, Rayfield EJ. Morphological evolution of the mammalian jaw adductor complex. Biol Rev Camb Philos Soc 2016; 92:1910-1940. [PMID: 27878942 PMCID: PMC6849872 DOI: 10.1111/brv.12314] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 10/12/2016] [Accepted: 10/17/2016] [Indexed: 11/29/2022]
Abstract
The evolution of the mammalian jaw during the transition from non‐mammalian synapsids to crown mammals is a key event in vertebrate history and characterised by the gradual reduction of its individual bones into a single element and the concomitant transformation of the jaw joint and its incorporation into the middle ear complex. This osteological transformation is accompanied by a rearrangement and modification of the jaw adductor musculature, which is thought to have allowed the evolution of a more‐efficient masticatory system in comparison to the plesiomorphic synapsid condition. While osteological characters relating to this transition are well documented in the fossil record, the exact arrangement and modifications of the individual adductor muscles during the cynodont–mammaliaform transition have been debated for nearly a century. We review the existing knowledge about the musculoskeletal evolution of the mammalian jaw adductor complex and evaluate previous hypotheses in the light of recently documented fossils that represent new specimens of existing species, which are of central importance to the mammalian origins debate. By employing computed tomography (CT) and digital reconstruction techniques to create three‐dimensional models of the jaw adductor musculature in a number of representative non‐mammalian cynodonts and mammaliaforms, we provide an updated perspective on mammalian jaw muscle evolution. As an emerging consensus, current evidence suggests that the mammal‐like division of the jaw adductor musculature (into deep and superficial components of the m. masseter, the m. temporalis and the m. pterygoideus) was completed in Eucynodontia. The arrangement of the jaw adductor musculature in a mammalian fashion, with the m. pterygoideus group inserting on the dentary was completed in basal Mammaliaformes as suggested by the muscle reconstruction of Morganucodon oehleri. Consequently, transformation of the jaw adductor musculature from the ancestral (‘reptilian’) to the mammalian condition must have preceded the emergence of Mammalia and the full formation of the mammalian jaw joint. This suggests that the modification of the jaw adductor system played a pivotal role in the functional morphology and biomechanical stability of the jaw joint.
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Affiliation(s)
- Stephan Lautenschlager
- School of Earth Sciences, University of Bristol, Bristol, BS8 1TQ, U.K.,School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, U.K
| | - Pamela Gill
- School of Earth Sciences, University of Bristol, Bristol, BS8 1TQ, U.K.,Earth Science Department, The Natural History Museum, London, SW7 5BD, U.K
| | - Zhe-Xi Luo
- Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL, 60637, U.S.A
| | - Michael J Fagan
- School of Engineering, University of Hull, Hull, HU6 7RX, U.K
| | - Emily J Rayfield
- School of Earth Sciences, University of Bristol, Bristol, BS8 1TQ, U.K
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26
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Martinelli AG, Soares MB, Schwanke C. Two New Cynodonts (Therapsida) from the Middle-Early Late Triassic of Brazil and Comments on South American Probainognathians. PLoS One 2016; 11:e0162945. [PMID: 27706191 PMCID: PMC5051967 DOI: 10.1371/journal.pone.0162945] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 08/26/2016] [Indexed: 12/02/2022] Open
Abstract
We describe two new cynodonts from the early Late Triassic of southern Brazil. One taxon, Bonacynodon schultzi gen. et sp. nov., comes from the lower Carnian Dinodontosaurus AZ, being correlated with the faunal association at the upper half of the lower member of the Chañares Formation (Ischigualasto-Villa Unión Basin, Argentina). Phylogenetically, Bonacynodon is a closer relative to Probainognathus jenseni than to any other probainognathian, bearing conspicuous canines with a denticulate distal margin. The other new taxon is Santacruzgnathus abdalai gen. et sp. nov. from the Carnian Santacruzodon AZ. Although based exclusively on a partial lower jaw, it represents a probainognathian close to Prozostrodon from the Hyperodapedon AZ and to Brasilodon, Brasilitherium and Botucaraitherium from the Riograndia AZ. The two new cynodonts and the phylogenetic hypothesis presented herein indicate the degree to which our knowledge on probainognathian cynodonts is incomplete and also the relevance of the South American fossil record for understanding their evolutionary significance. The taxonomic diversity and abundance of probainognathians from Brazil and Argentina will form the basis of deep and complex studies to address the evolutionary transformations of cynodonts leading to mammals.
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Affiliation(s)
- Agustín G. Martinelli
- Laboratório de Paleontologia de Vertebrados, Departamento de Paleontologia e Estratigrafia, Instituto de Geociências, Universidade Federal do Rio Grande do Sul (UFRGS), Ave. Bento Gonçalves 9500, Agronomia, 91540–000, Porto Alegre, RS, Brazil
| | - Marina Bento Soares
- Laboratório de Paleontologia de Vertebrados, Departamento de Paleontologia e Estratigrafia, Instituto de Geociências, Universidade Federal do Rio Grande do Sul (UFRGS), Ave. Bento Gonçalves 9500, Agronomia, 91540–000, Porto Alegre, RS, Brazil
| | - Cibele Schwanke
- Instituto Federal de Educação, Ciência e Tecnologia do Rio Grande do Sul, Campus Porto Alegre, Rua Coronel Vicente 281, Centro Histórico, 90030–040, Porto Alegre, RS, Brazil
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27
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Jasinoski SC, Abdala F. Cranial Ontogeny of the Early Triassic Basal Cynodont Galesaurus planiceps. Anat Rec (Hoboken) 2016; 300:353-381. [PMID: 27615281 DOI: 10.1002/ar.23473] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Revised: 06/20/2016] [Accepted: 06/22/2016] [Indexed: 01/25/2023]
Abstract
Ontogenetic changes in the skull and mandible of thirty-one specimens of Galesaurus planiceps, a basal non-mammaliaform cynodont from the Early Triassic of South Africa, are documented. The qualitative survey indicated eight changes in the craniomandibular apparatus occurred during growth, dividing the sample into three ontogenetic stages: juvenile, subadult, and adult. Changes in the temporal region, zygomatic arch, occiput, and mandible occurred during the transition from the subadult to adult stage at a basal skull length of 90 mm. At least four morphological and allometric differences divided the adult specimens into two morphs, indicating the presence of sexual dimorphism in Galesaurus. Differences include extensive lateral flaring of the zygomatic arches in the "male" morph resulting in a more anterior orientation of the orbits, and a narrower snout in the "female". This is the first record of sexual dimorphism in a basal cynodont, and the first time it is quantitatively documented in a non-mammaliaform cynodont. An ontogenetic comparison between Galesaurus and the more derived basal cynodont Thrinaxodon revealed differences in the timing and extent of sagittal crest development. In Galesaurus, the posterior sagittal crest, located behind the parietal foramen, developed relatively later in ontogeny, and the anterior sagittal crest rarely formed suggesting the anterior fibres of the temporalis were less developed than in Thrinaxodon. In contrast, craniomandibular features related to the masseters became more developed during the ontogeny of Galesaurus. The development of the adductor musculature appears to be one of the main factors influencing skull growth in these basal non-mammaliaform cynodonts. Anat Rec, 300:353-381, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Sandra C Jasinoski
- 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
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28
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Palci A, Lee MSY, Hutchinson MN. Patterns of postnatal ontogeny of the skull and lower jaw of snakes as revealed by micro-CT scan data and three-dimensional geometric morphometrics. J Anat 2016; 229:723-754. [PMID: 27329823 DOI: 10.1111/joa.12509] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/17/2016] [Indexed: 12/17/2022] Open
Abstract
We compared the head skeleton (skull and lower jaw) of juvenile and adult specimens of five snake species [Anilios (=Ramphotyphlops) bicolor, Cylindrophis ruffus, Aspidites melanocephalus, Acrochordus arafurae, and Notechis scutatus] and two lizard outgroups (Ctenophorus decresii, Varanus gilleni). All major ontogenetic changes observed were documented both qualitatively and quantitatively. Qualitative comparisons were based on high-resolution micro-CT scanning of the specimens, and detailed quantitative analyses were performed using three-dimensional geometric morphometrics. Two sets of landmarks were used, one for accurate representation of the intraspecific transformations of each skull and jaw configuration, and the other for comparison between taxa. Our results document the ontogenetic elaboration of crests and processes for muscle attachment (especially for cervical and adductor muscles); negative allometry in the braincase of all taxa; approximately isometric growth of the snout of all taxa except Varanus and Anilios (positively allometric); and positive allometry in the quadrates of the macrostomatan snakes Aspidites, Acrochordus and Notechis, but also, surprisingly, in the iguanian lizard Ctenophorus. Ontogenetic trajectories from principal component analysis provide evidence for paedomorphosis in Anilios and peramorphosis in Acrochordus. Some primitive (lizard-like) features are described for the first time in the juvenile Cylindrophis. Two distinct developmental trajectories for the achievement of the macrostomatan (large-gaped) condition in adult snakes are documented, driven either by positive allometry of supratemporal and quadrate (in pythons), or of quadrate alone (in sampled caenophidians); this is consistent with hypothesised homoplasy in this adaptive complex. Certain traits (e.g. shape of coronoid process, marginal tooth counts) are more stable throughout postnatal ontogeny than others (e.g. basisphenoid keel), with implications for their reliability as phylogenetic characters.
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Affiliation(s)
- Alessandro Palci
- South Australian Museum, Adelaide, SA, Australia.,School of Biological Sciences, Flinders University, Adelaide, SA, Australia
| | - Michael S Y Lee
- South Australian Museum, Adelaide, SA, Australia.,School of Biological Sciences, Flinders University, Adelaide, SA, Australia
| | - Mark N Hutchinson
- South Australian Museum, Adelaide, SA, Australia.,School of Biological Sciences, Flinders University, Adelaide, SA, Australia.,School of Biological Sciences, University of Adelaide, Adelaide, SA, Australia
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Benoit J, Abdala F, Van den Brandt MJ, Manger PR, Rubidge BS. Physiological implications of the abnormal absence of the parietal foramen in a late Permian cynodont (Therapsida). Naturwissenschaften 2015; 102:69. [PMID: 26538062 DOI: 10.1007/s00114-015-1321-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 08/10/2015] [Accepted: 10/26/2015] [Indexed: 11/29/2022]
Abstract
The third eye (pineal eye), an organ responsible for regulating exposure to sunlight in extant ectotherms, is located in an opening on the dorsal surface of the skull, the parietal foramen. The parietal foramen is absent in extant mammals but often observed in basal therapsids, the stem-group to true mammals. Here, we report the absence of the parietal foramen in a specimen of Cynosaurus suppostus, a Late Permian cynodont from South Africa (SA). Comparison with Procynosuchus delaharpeae, a contemporaneous non-mammalian cynodont from SA, demonstrates that the absence of this foramen is an abnormal condition for such a basal species. Because seasonality was marked during the Late Permian in SA, it is proposed that the third eye was functionally redundant in Cynosaurus, possibly due to the acquisition of better thermoregulation or the evolution of specialized cells in the lateral eyes to compensate for the role of the third eye.
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Affiliation(s)
- Julien Benoit
- Evolutionary Studies Institute (ESI), School of Geosciences, University of the Witwatersrand, Braamfontein, 2050, Johannesburg, South Africa. .,School of Anatomical Sciences, University of the Witwatersrand, 7 York Road, Parktown, 2193, Johannesburg, South Africa.
| | - Fernando Abdala
- Evolutionary Studies Institute (ESI), School of Geosciences, University of the Witwatersrand, Braamfontein, 2050, Johannesburg, South Africa
| | - Marc J Van den Brandt
- Evolutionary Studies Institute (ESI), School of Geosciences, University of the Witwatersrand, Braamfontein, 2050, Johannesburg, South Africa
| | - Paul R Manger
- School of Anatomical Sciences, University of the Witwatersrand, 7 York Road, Parktown, 2193, Johannesburg, South Africa
| | - Bruce S Rubidge
- Evolutionary Studies Institute (ESI), School of Geosciences, University of the Witwatersrand, Braamfontein, 2050, Johannesburg, South Africa.,School for Geosciences, University of the Witwatersrand, Braamfontein, 2050, Johannesburg, South Africa
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