Tooth replacement in the non-mammalian cynodont <i>Cynosaurus suppostus</i> (Therapsida) from the late Permian of South Africa

Norton, Luke A.; Abdala, Fernando; Rubidge, Bruce S.; Botha‐Brink, Jennifer

doi:10.1080/02724634.2021.2001650

Cited by 4 publications

(11 citation statements)

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“…(133): "Posterior postcanine accessory cusp number: two (0), one (1), greater than two (2)." In charassognathids, Procynosuchus, Cynosaurus, Platycraniellus, Bolotridon, and the gomphodonts Trirachodon kannemeyeri and Boreogomphodon, the posterior postcanines bear two accessory cusps (e.g., Abdala, 2007;Botha et al, 2007;Huttenlocker & Sidor, 2020;Kammerer, 2016;Kemp, 1979;Liu & Sues, 2010;Norton et al, 2021;Pusch et al, 2021;Sidor & Hopson, 2018;van den Brandt & Abdala, 2018;van Heerden & Rubidge, 1990). The galesaurids Progalesaurus and Galesaurus have a unique postcanine morphology among epicynodonts, in which the postcanines bear only a single accessory cusp with the larger main (mesial) cusp curving distally over the smaller accessory (distal) cusp (Figure 1j,k) (Norton et al, 2020;Pusch et al, 2019;Sidor & Smith, 2004).…”

Section: Discrete Characters Of the Lower Jaw And Dentitionmentioning

confidence: 99%

“…This technology has been instrumental in understanding such topics as tooth replacement, internal snout and braincase morphology, brain and bony labyrinth evolution, facial innervation, and the origins of endothermy in synapsids. Although endocranial characters have been described for various therapsids in CT-assisted studies in recent years (e.g., Araújo et al, 2017Araújo et al, , 2018Bendel et al, 2018;Benoit et al, 2018Benoit et al, , 2019Benoit et al, , 2021Benoit et al, , 2022Benoit, Jasinoski, Fernandez, & Abdala, 2017;Benoit, Manger, Fernandez, & Rubidge, 2016, 2017Castanhinha et al, 2013;Duhamel et al, 2021;Gigliotti et al, 2023;Laaß, 2015aLaaß, , 2015bLaaß, , 2016Pusch et al, 2020), with special focus on cynodonts due to their importance for mammal origins (e.g., Abdala et al, 2013;Benoit, 2023;Crompton, 2013;Crompton et al, 2015;Crompton, Owerkowicz, et al, 2017;Huttenlocker & Sidor, 2020;Jasinoski et al, 2015;Kemp, 2009;Kerber et al, 2021Kerber et al, , 2024Norton et al, 2020Norton et al, , 2021Pavanatto et al, 2019;Pusch et al, 2019Pusch et al, , 2021Pusch et al, , 2023Rodrigues et al, 2013Rodrigues et al, , 2014Rodrigues et al, , 2018Rowe et al, 1995…”

Section: Introductionmentioning

confidence: 99%

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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

Pusch,

Kammerer,

Fröbisch

2024

The Anatomical Record

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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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Section: Discrete Characters Of the Lower Jaw And Dentitionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Pusch,

Kammerer,

Fröbisch

2024

The Anatomical Record

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“…Mammals also developed a unique type of dental occlusion (accompanied by fleshy cheeks and chewing as indicated by the presence of a masseteric fossa on the dentary) [13]. Numerous studies investigating tooth replacement patterns in NMC and NMM have been undertaken, using X-ray microtomography (CT) scanning [14][15][16] and histological sectioning [17,18], and have had converging results. The NMC display a wide variety of conditions of dental succession [14][15][16], but there is no definite evidence of diphyodonty in NMC [14][15][16].…”

Section: Tooth Replacement and Diphyodontymentioning

confidence: 99%

“…Numerous studies investigating tooth replacement patterns in NMC and NMM have been undertaken, using X-ray microtomography (CT) scanning [14][15][16] and histological sectioning [17,18], and have had converging results. The NMC display a wide variety of conditions of dental succession [14][15][16], but there is no definite evidence of diphyodonty in NMC [14][15][16]. Although this style of tooth replacement has recently been proposed for the mammalian-proximate taxon Brasilodon [18], the evidence presented is not compelling, and previous studies have indicated that dental replacement was not diphyodont in that taxon [19,20].…”

Section: Tooth Replacement and Diphyodontymentioning

confidence: 99%

Craniodental anatomy in Permian–Jurassic Cynodontia and Mammaliaformes (Synapsida, Therapsida) as a gateway to defining mammalian soft tissue and behavioural traits

Norton

Abdala

Benoît

2023

Phil. Trans. R. Soc. B

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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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“…Most studies on the tooth replacement and growth patterns in non-mammaliaform cynodonts were mainly based on the use of bone/tooth histology methods (e.g., Melo et al, 2019;O'Meara et al, 2018;Poole, 1956), assessment of ontogenetic series (e.g., Hopson, 1964;Parrington, 1936), or tooth crown morphology (e.g., Crompton & Luo, 1993;Gow, 1980;Grine, 1977;Martinelli & Bonaparte, 2011;Pacheco et al, 2017). More recently, nondestructive methods (e.g., computed tomography) are being applied in paleontological research to access morphological information previously not available, providing accurate data about tooth morphology and replacement patterns in nonmammaliaform cynodonts (e.g., Abdala et al, 2013;Norton et al, 2020Norton et al, , 2021. However, only a few Triassic taxa from Brazil have been analyzed so far using this method (Stefanello et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

On the dentition, tooth replacement, and taxonomic status of Charruodon tetracuspidatus Abdala & Ribeiro, 2000: A bizarre cynodont from the middle upper Triassic of southern Brazil

Hoffmann,

Ribeiro,

de Andrade

2023

The Anatomical Record

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Among the living tetrapods, mammals present a unique tooth replacement pattern, diphyodonty. Therefore, studying the dentition of mammalian ancestors is relevant to a better understanding of how this remarkable feature evolved. However, little is known about the postcanine tooth replacement pattern among Triassic cynodonts. Here, we applied the nondestructive method of microcomputed tomography (microCT) to analyze the dentition of the enigmatic Upper Triassic sectorial‐toothed cynodont Charruodon tetracuspidatus (MCP 3934 PV, holotype) from the Candelaria Sequence, Santa Maria Supersequence, Brazil. The microCT‐scan data allowed visualization of the replacement dentition and roots of the functional teeth, which provided information to inform interpretations of the ontogenetic stage and taxonomy of the species. A combination of dental and mandibular traits, as well as the small size of the specimen MCP 3934 PV, suggest an early ontogenetic stage. Additionally, the specimen could potentially be an ontogenetically immature form of another taxon, or a yet unknown species of probainognathian cynodont. Therefore, Charruodon tetracuspidatus is here designated as a nomen dubium, given the challenges of maintaining the species as valid.

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Tooth replacement in the non-mammalian cynodont Cynosaurus suppostus (Therapsida) from the late Permian of South Africa

Cited by 4 publications

References 44 publications

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

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

Craniodental anatomy in Permian–Jurassic Cynodontia and Mammaliaformes (Synapsida, Therapsida) as a gateway to defining mammalian soft tissue and behavioural traits

On the dentition, tooth replacement, and taxonomic status of Charruodon tetracuspidatus Abdala & Ribeiro, 2000: A bizarre cynodont from the middle upper Triassic of southern Brazil

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