Permian hypercarnivore suggests dental complexity among early amniotes

Maho, Tea; Maho, Sigi; Scott, Diane; Reisz, Robert R.

doi:10.1038/s41467-022-32621-5

Cited by 7 publications

(14 citation statements)

References 37 publications

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“…This characteristic has also been noted for Mosasaurus, with the replacement teeth forming in the posterior-lingual PLOS ONE position [38]. Lastly, M. dianeae appears to have a long replacement period (192 days) and long-lived teeth (221 days), compared to other insectivorous species that have small, delicate teeth [47].…”

Section: Histologysupporting

confidence: 59%

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An intriguing new diapsid reptile with evidence of mandibulo-dental pathology from the early Permian of Oklahoma revealed by neutron tomography

et al. 2022

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The initial stages of diapsid evolution, the clade that includes extant reptiles and the majority of extinct reptilian taxa, is surprisingly poorly known. Notwithstanding the hypothesis that varanopids are diapsids rather than synapsids, there are only four araeoscelidians and one neodiapsid present in the late Carboniferous and early Permian. Here we describe the fragmentary remains of a very unusual new amniote from the famous cave deposits near Richards Spur, Oklahoma, that we recognize as a diapsid reptile, readily distinguishable from all other early amniotes by the unique dentition and lower jaw anatomy. The teeth have an unusual reeding pattern on the crown (long parallel ridges with rounded surfaces), with some teeth posteriorly tilted and strongly recurved, while a ventral protuberance forms the anterior terminus of the dentary. Overall, the lower jaw is unusually slender with a flattened ventral surface formed by the dentary and splenial anteriorly and the angular in the mid-region. The presence of a very slender triradiate jugal revealed through computed tomography confirms the existence of a large lower temporal fenestra, while the medial edge of the maxilla and the anatomy of the palatine confirm the presence of a large suborbital fenestra. Computed tomography of this new taxon reveals maxillary innervation that is characteristically reptile, not synapsid. Although no other definitively identifiable skull roof elements exist, the suborbital fenestra borders preserved on the palatine and maxilla supports the hypothesis that this is a diapsid reptile. Interestingly, the right dentary shows evidence of pathology, a rarely reported occurrence in Paleozoic amniotes, with several empty tooth sockets filled by bone. This small predator with delicate subthecodont implanted dentition provides strong evidence that diapsid reptiles were already diversifying rapidly in the early Permian, but likely were relatively rare members of terrestrial vertebrate assemblages.

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Section: Histologysupporting

confidence: 59%

“…Lastly, M . dianeae appears to have a long replacement period (192 days) and long-lived teeth (221 days), compared to other insectivorous species that have small, delicate teeth [ 47 ].…”

Section: Discussionmentioning

confidence: 99%

An intriguing new diapsid reptile with evidence of mandibulo-dental pathology from the early Permian of Oklahoma revealed by neutron tomography

et al. 2022

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“…Dumont et al, 2016; Garcia & Zurriaguz, 2016; Heckeberg & Rauhut, 2020; Kear et al, 2017), variations in the von Ebner count between functional and replacement teeth allow the inference of rates of tooth replacement in fossil amniotes (e.g. D'Emic et al, 2013, 2019; Erickson, 1996a; Maho et al, 2022).…”

Section: Discussionmentioning

confidence: 99%

Palaeohistology reveals an unusual periodontium and tooth implantation in a filter‐feeding pterodactyloid pterosaur, Pterodaustro guinazui, from the Lower Cretaceous of Argentina

Cerda

Codorniú

2023

Journal of Anatomy

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Pterosaurs are an extinct group of Mesozoic flying reptiles, which exhibited high diversity with regard to their dentition. Although morphological features of pterosaur dentition have been described in detail in several contributions, the histology of tooth and tooth attachment tissues (i.e. periodontium) has been scarcely analysed to date for this clade. Here we describe and interpret the microstructure of the tooth and periodontium attachment tissues of Pterodaustro guinazui, a filter‐feeding pterodactyloid pterosaur from the Lower Cretaceous of Argentina. The histological analysis of the lower jaw and its filamentous teeth verifies that the geometry of the implantation corresponds to an aulacodont condition (i.e. teeth are set in a groove with no interdental separation). This pattern departs from that recorded in other archosaurs, being possibly also present in other, non‐closely related, pterosaurs. Regarding tooth attachment, in contrast to other pterosaurs, there is no direct evidence for gomphosis in Pterodaustro (i.e. the absence of cementum, mineralized periodontal ligamentum and alveolar bone). Nevertheless, the current evidence for ankylosis is still not conclusive. Contrary to that reported for other archosaurs, replacement teeth are absent in Pterodaustro, which is interpreted as evidence for monophyodonty or diphyodonty in this taxon. Most of the microstructural features are possibly related to the complex filter‐feeding apparatus of Pterodaustro and does not appear to represent the general pattern of pterosaurs.

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“…It is also considered homologous among amniotes due to the morphological similarities (alternating opaque zones, line trajectories paralleling the contour of the pulp cavity, and widths ranging between 1 and 30 μm) observed between mammals, crocodilians, dinosaurs, mosasaurs, early synapsids, early reptiles and stem‐amniotes (Erickson 1996a, 1996b; Hillson 2005, 2014; Gren & Lindgren 2014; García & Zurriaguz 2016; Maho et al . 2022). In non‐amniote vertebrates, incremental lines have been identified in non‐amniote osteichthyans (e.g.…”

Section: Discussionmentioning

confidence: 99%

Developmental models shed light on the earliest dental tissues, using Astraspis as an example

Houée,

Bardin,

Germain

et al. 2023

Palaeontology

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Fossils of extinct jawless vertebrates are pivotal to deciphering the evolutionary paths that led to the various forms of the vertebrate skeleton. For example, Pteraspidomorphs (stem‐gnathostomes), such as the Ordovician Astraspis, display some of the oldest remains of bony and ‘dental’ (dentine and enameloid) tissues. However, the identification of the very nature of these early mineralized tissues has been hampered by a lack of unambiguous diagnostic characters. As development is key to identifying the derivation of these tissues, we developed an integrative and generic histogenetic model, testing several ontogenetic scenarios. We illustrate our approach on the basis of the well‐preserved Astraspis samples and show how this can be used to infer key developmental features from extinct species. This study suggests that in the odontodes of Astraspis: (1) the initial curvature of the epithelium was close to the shape of the final external surface; (2) the mesenchymal cells differentiate synchronously in the whole inner periphery; and (3) the capping tissue was produced by both mesenchymal and epithelial cells (enameloid rather than enamel). Astraspis specimens also provide evidence of a dual growth periodicity, possibly homologous to Andresen and von Ebner growth lines observed in amniotes, suggesting this type of dual periodicity may be shared by most vertebrates. We estimated that an Astraspis odontode grew up in around 60–70 days at a rate of 0.5–5 μm/day. The new developmental approach proposed in this study could be a robust framework for critically evaluating the tissues of extinct taxa in the future.

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Permian hypercarnivore suggests dental complexity among early amniotes

Cited by 7 publications

References 37 publications

An intriguing new diapsid reptile with evidence of mandibulo-dental pathology from the early Permian of Oklahoma revealed by neutron tomography

An intriguing new diapsid reptile with evidence of mandibulo-dental pathology from the early Permian of Oklahoma revealed by neutron tomography

Palaeohistology reveals an unusual periodontium and tooth implantation in a filter‐feeding pterodactyloid pterosaur, Pterodaustro guinazui, from the Lower Cretaceous of Argentina

Developmental models shed light on the earliest dental tissues, using Astraspis as an example

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