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Stuart BP, Huttenlocker AK, Botha J. The postcranial anatomy of Moschorhinus kitchingi (Therapsida: Therocephalia) from the Karoo Basin of South Africa. PeerJ 2024; 12:e17765. [PMID: 39148680 PMCID: PMC11326434 DOI: 10.7717/peerj.17765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2024] [Accepted: 06/26/2024] [Indexed: 08/17/2024] Open
Abstract
Therocephalia are an important clade of non-mammalian therapsids that evolved a diverse array of morphotypes and body sizes throughout their evolutionary history. The postcranial anatomy of therocephalians has largely been overlooked, but remains important towards understanding aspects of their palaeobiology and phylogenetic relationships. Here, we provide the first postcranial description of the large akidnognathid eutherocephalian Moschorhinus kitchingi by examining multiple specimens from fossil collections in South Africa. We also compare the postcranial anatomy with previously described therocephalian postcranial material and provide an updated literature review to ensure a reliable foundation of comparison for future descriptive work. Moschorhinus shares all the postcranial features of eutherocephalians that differentiate them from early-diverging therocephalians, but is differentiated from other eutherocephalian taxa by aspects concerning the scapula, interclavicle, sternum, manus, and femur. The novel anatomical data from this contribution shows that Moschorhinus possessed a stocky bauplan with a particularly robust scapula, humerus, and femur. These attributes, coupled with the short and robust skull bearing enlarged conical canines imply that Moschorhinus was well equipped to grapple with and subdue prey items. Additionally, the combination of these attributes differ from those of similarly sized coeval gorgonopsians, which would have occupied a similar niche in late Permian ecosystems. Moreover, Moschorhinus was the only large carnivore known to have survived the Permo-Triassic mass extinction. Thus, the subtle but important postcranial differences may suggest a type of niche partitioning in the predator guild during the Permo-Triassic mass extinction interval.
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Affiliation(s)
- Brandon P Stuart
- Department of Zoology and Entomology, University of the Free State, Bloemfontein, Free State, South Africa
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, Gauteng, South Africa
- School of Geosciences, University of the Witwatersrand, Johannesburg, Gauteng, South Africa
| | - Adam K Huttenlocker
- Department of Integrative Anatomical Sciences, University of Southern California, Los Angeles, California, United States
| | - Jennifer Botha
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, Gauteng, South Africa
- School of Geosciences, University of the Witwatersrand, Johannesburg, Gauteng, South Africa
- University of the Witwatersrand, GENUS: DSI-NRF Centre of Excellence in Palaeosciences, Johannesburg, Gauteng, South Africa
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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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Kaiuca JFL, Martinelli AG, Schultz CL, Fonseca PHM, Tavares WC, Soares MB. Weighing in on miniaturization: New body mass estimates for Triassic eucynodonts and analyses of body size evolution during the cynodont-mammal transition. Anat Rec (Hoboken) 2024; 307:1594-1612. [PMID: 38229416 DOI: 10.1002/ar.25377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Revised: 12/20/2023] [Accepted: 12/22/2023] [Indexed: 01/18/2024]
Abstract
Body size influences most aspects of an animal's biology, consequently, evolutionary diversification is often accompanied by differentiation of body sizes within a lineage. It is accepted that miniaturization, or the evolution of extremely small body sizes, played a key role in the origin and early evolution of different mammalian characters in non-mammaliaform cynodonts. However, while there are multiple studies on the biomechanical, behavioral, and physiological consequences of smaller sizes, few explore the evolutionary processes that lead to them. Here, we use body mass as a universal size measurement in phylogenetic comparative analyses to explore aspects of body size evolution in Cynodontia, focusing on the cynodont-mammal transition, and test the miniaturization hypothesis for the origin of Mammaliaformes. We estimated the body masses of 29 species, ranging from Theriocephalia to Mammaliaformes, providing the largest collection of Triassic cynodont body mass estimates that we know of, and used these estimates in analyses of disparity through time and RRphylo . Unexpectedly, our results did not support the miniaturization hypothesis. Even though cynodont body size disparity fell during the Late Triassic, and remained lower than expected under a purely Brownian motion model of evolution up until the Early Jurassic, we found that rates of body size evolution were significantly lower in prozostrodontians leading to the first Mammaliaformes than in other lineages. Evolution rates were higher in medium and large-sized taxa, indicating that size was changing more rapidly in those lineages and that small sizes were probably a persistent plesiomorphic character-state in Cynodontia.
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Affiliation(s)
- João Felipe Leal Kaiuca
- Programa de Pós-Graduação em Biodiversidade e Biologia Evolutiva, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Instituto de Biologia, Interbloco B/C, CCS, Rio de Janeiro, Brazil
- Núcleo Multidisciplinar de Pesquisa em Biologia, Campus UFRJ Duque de Caxias Professor Geraldo Cidade, Universidade Federal do Rio de Janeiro, Duque de Caxias, Brazil
- Departamento de Geologia e Paleontologia, Museu Nacional, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Agustín Guillermo Martinelli
- Sección Paleontología de Vertebrados, Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"-CONICET, Buenos Aires, Argentina
| | - Cesar Leandro Schultz
- Departamento de Paleontologia e Estratigrafia, Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Pedro Henrique Morais Fonseca
- Programa de Pós-Graduação em Geociências, Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - William Corrêa Tavares
- Programa de Pós-Graduação em Biodiversidade e Biologia Evolutiva, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Instituto de Biologia, Interbloco B/C, CCS, Rio de Janeiro, Brazil
- Núcleo Multidisciplinar de Pesquisa em Biologia, Campus UFRJ Duque de Caxias Professor Geraldo Cidade, Universidade Federal do Rio de Janeiro, Duque de Caxias, Brazil
| | - Marina Bento Soares
- Departamento de Geologia e Paleontologia, Museu Nacional, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
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Shi YT, Liu J. The tetrapod fauna of the upper Permian Naobaogou Formation of China: 10. Jimusaria monanensis sp. nov. (Dicynodontia) shows a unique epipterygoid. PeerJ 2023; 11:e15783. [PMID: 37547715 PMCID: PMC10399559 DOI: 10.7717/peerj.15783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Accepted: 07/03/2023] [Indexed: 08/08/2023] Open
Abstract
Jimusaria is the first reported Chinese dicynodont, previously only known from Xinjiang. Here we refer two specimens from the Naobaogou Formation, Nei Mongol, China to Jimusaria based on the following features: squamosal separated from supraoccipital by tabular, tabular contacting opisthotic, sharp and thin lateral dentary shelf expanding anteriorly into a thick swelling, nasals fused as single element, rod-like medial bar formed by footplate of epipterygoid connecting to the parabasisphenoid and periotic medially. A new species, J. monanensis, is named based on the diagnostic characters on these two specimens such as distinct caniniform buttress lacking posteroventral furrow, naso-frontal suture forming an anterior directed sharp angle, and converging ventral ridges on posterior portion of anterior pterygoid rami. In Jimusaria, the epipterygoid posteromedially contacts the parabasisphenoid and the periotic as a rod-like bar, a unique morphology unknown in any other dicynodonts. This structure probably increases the stability of the palatal complex. A similar structure might also appear in other dicynodonts as a cartilage connection. The new occurrence of Jimusaria increases the diversity of the tetrapod assemblage from the Naobaogou Formation, and further strengthens the connection between the tetrapod faunas from Nei Mongol and Xinjiang. Based on the current record, Jimusaria is one of the few tetrapod genera which survived in the end-Permian mass extinction.
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Affiliation(s)
- Yu-Tai Shi
- 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
| | - 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
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Kammerer CF, Viglietti PA, Butler E, Botha J. Rapid turnover of top predators in African terrestrial faunas around the Permian-Triassic mass extinction. Curr Biol 2023:S0960-9822(23)00455-4. [PMID: 37220743 DOI: 10.1016/j.cub.2023.04.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 03/19/2023] [Accepted: 04/05/2023] [Indexed: 05/25/2023]
Abstract
Catastrophic ecosystem disruption in the late Permian period resulted in the greatest loss of biodiversity in Earth's history, the Permian-Triassic mass extinction (PTME).1 The dominant terrestrial vertebrates of the Permian (synapsids) suffered major losses at this time, leading to their replacement by reptiles in the Triassic.2 The dominant late Permian predatory synapsids, gorgonopsians, were completely extirpated by the PTME. The largest African gorgonopsians, the Rubidgeinae, have traditionally been assumed to go extinct at the Permo-Triassic boundary (PTB).3,4,5 However, this apparent persistence through the sustained extinction interval characterizing the continental PTME6 is at odds with ecological theory indicating that top predators have high extinction risk.7 Here, we report the youngest known large-bodied gorgonopsians, gigantic specimens from the PTB site of Nooitgedacht 68 in South Africa. These specimens are not rubidgeine, and instead are referable to Inostrancevia, a taxon previously thought to be a Russian endemic.8 Based on comprehensive review of the South African gorgonopsian record, we show that rubidgeines were early victims of ecosystem disruption preceding the PTME and were replaced as top predators by Laurasian immigrant inostranceviines. The reign of this latter group was short-lived, however; by the PTB, gorgonopsians were extinct, and a different group (therocephalians) became the largest synapsid predators, before themselves going extinct. The extinction and replacement of top predators in rapid succession at the clade level underlines the extreme degree of ecosystem instability in the latest Permian and earliest Triassic, a phenomenon that was likely global in extent.
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Affiliation(s)
- Christian F Kammerer
- North Carolina Museum of Natural Sciences, 11 West Jones Street, Raleigh, NC 27601, USA; Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA; Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg 2050, South Africa.
| | - Pia A Viglietti
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg 2050, South Africa; Negaunee Integrative Research Center, Field Museum of Natural History, 1400 South DuSable Lake Shore Drive, Chicago, IL 60605, USA
| | - Elize Butler
- National Museum, 36 Aliwal Street, Bloemfontein 9301, South Africa
| | - Jennifer Botha
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg 2050, South Africa; GENUS: DSI-NRF Centre of Excellence in Palaeosciences, Johannesburg 2050, South Africa
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