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Hu J, Xu X, Li F, Han F. Tooth replacement in the early-diverging neornithischian Jeholosaurus shangyuanensis and implications for dental evolution and herbivorous adaptation in Ornithischia. BMC Ecol Evol 2024; 24:46. [PMID: 38627692 PMCID: PMC11020315 DOI: 10.1186/s12862-024-02233-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Accepted: 03/28/2024] [Indexed: 04/19/2024] Open
Abstract
BACKGROUND Tooth replacement patterns of early-diverging ornithischians, which are important for understanding the evolution of the highly specialized dental systems in hadrosaurid and ceratopsid dinosaurs, are poorly known. The early-diverging neornithischian Jeholosaurus, a small, bipedal herbivorous dinosaur from the Early Cretaceous Jehol Biota, is an important taxon for understanding ornithischian dental evolution, but its dental morphology was only briefly described previously and its tooth replacement is poorly known. RESULTS CT scanning of six specimens representing different ontogenetic stages of Jeholosaurus reveals significant new information regarding the dental system of Jeholosaurus, including one or two replacement teeth in nearly all alveoli, relatively complete tooth resorption, and an increase in the numbers of alveoli and replacement teeth during ontogeny. Reconstructions of Zahnreihen indicate that the replacement pattern of the maxillary dentition is similar to that of the dentary dentition but with a cyclical difference. The maxillary tooth replacement rate in Jeholosaurus is probably 46 days, which is faster than that of most other early-diverging ornithischians. During the ontogeny of Jeholosaurus, the premaxillary tooth replacement rate slows from 25 days to 33 days with similar daily dentine formation. CONCLUSIONS The tooth replacement rate exhibits a decreasing trend with ontogeny, as in Alligator. In a phylogenetic context, fast tooth replacement and multi-generation replacement teeth have evolved at least twice independently in Ornithopoda, and our analyses suggest that the early-diverging members of the major ornithischian clades exhibit different tooth replacement patterns as an adaption to herbivory.
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Affiliation(s)
- Jinfeng Hu
- School of Earth Sciences, China University of Geosciences, 388 Lumo Road, 430074, Wuhan, Hubei Province, China
| | - Xing Xu
- Center for Vertebrate Evolutionary Biology, Yunnan University, Kunming, China
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China
| | - Fuqiang Li
- Yifu Museum of China University of Geosciences, Wuhan, Hubei, China
| | - Fenglu Han
- School of Earth Sciences, China University of Geosciences, 388 Lumo Road, 430074, Wuhan, Hubei Province, China.
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Maho T, Reisz RR. Exceptionally rapid tooth development and ontogenetic changes in the feeding apparatus of the Komodo dragon. PLoS One 2024; 19:e0295002. [PMID: 38324523 PMCID: PMC10849390 DOI: 10.1371/journal.pone.0295002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Accepted: 11/14/2023] [Indexed: 02/09/2024] Open
Abstract
Dental developmental and replacement patterns in extinct amniotes have attracted a lot of attention. Notable among these are Paleozoic predatory synapsids, but also Mesozoic theropod dinosaurs, well known for having true ziphodonty, strongly serrated carinae with dentine cores within an enamel cap. The Komodo dragon, Varanus komodoensis, is the only extant terrestrial vertebrate to exhibit true ziphodonty, making it an ideal model organism for gaining new insights into the life history and feeding behaviours of theropod dinosaurs and early synapsids. We undertook a comparative dental histological analysis of this extant apex predator in combination with computed tomography of intact skulls. This study allowed us to reconstruct the dental morphology, ontogeny, and replacement patterns in the largest living lizard with known feeding behaviour, and apply our findings to extinct taxa where the behaviour is largely unknown. We discovered through computed tomography that V. komodoensis maintains up to five replacement teeth per tooth position, while histological analysis showed an exceptionally rapid formation of new teeth, every 40 days. Additionally, a dramatic ontogenetic shift in the dental morphology of V. komodoensis was also discovered, likely related to changes in feeding preferences and habitat. The juveniles have fewer dental specializations, lack true ziphodonty, are arboreal and feed mostly on insects, whereas the adults have strongly developed ziphodonty and are terrestrial apex predators with defleshing feeding behaviour. In addition, we found evidence that the ziphodont teeth of V. komodoensis have true ampullae (interdental folds for strengthening the serrations), similar to those found only in theropod dinosaurs. Comparisons with other species of Varanus and successive outgroup taxa reveal a complex pattern of dental features and adaptations, including the evolution of snake-like tongue flicking used for foraging for prey. However, only the Komodo dragon exhibits this remarkable set of dental innovations and specializations among squamates.
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Affiliation(s)
- Tea Maho
- International Center of Future Science, Jilin University, Changchun, Jilin Province, China
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada
| | - Robert R. Reisz
- International Center of Future Science, Jilin University, Changchun, Jilin Province, China
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada
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3
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Cerda IA, Codorniú L. Palaeohistology reveals an unusual periodontium and tooth implantation in a filter-feeding pterodactyloid pterosaur, Pterodaustro guinazui, from the Lower Cretaceous of Argentina. J Anat 2023; 243:579-589. [PMID: 37059589 PMCID: PMC10485577 DOI: 10.1111/joa.13878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 03/30/2023] [Accepted: 03/31/2023] [Indexed: 04/16/2023] Open
Abstract
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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Affiliation(s)
- Ignacio A Cerda
- Consejo Nacional de Investigación Ciencia y Técnica (CONICET), Buenos Aires, Argentina
- Instituto de Investigación en Paleobiología y Geología (IIPG), Universidad Nacional de Río Negro (UNRN), Museo Carlos Ameghino, Cipolletti, Río Negro, Argentina
| | - Laura Codorniú
- Consejo Nacional de Investigación Ciencia y Técnica (CONICET), Buenos Aires, Argentina
- Departamento de Geología, Universidad Nacional de San Luis, San Luis, Argentina
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Ballell A, Benton MJ, Rayfield EJ. Dental form and function in the early feeding diversification of dinosaurs. SCIENCE ADVANCES 2022; 8:eabq5201. [PMID: 36525501 PMCID: PMC9757754 DOI: 10.1126/sciadv.abq5201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Revised: 07/05/2022] [Accepted: 11/16/2022] [Indexed: 06/17/2023]
Abstract
Dinosaurs evolved a remarkable diversity of dietary adaptations throughout the Mesozoic, but the origins of different feeding modes are uncertain, especially the multiple origins of herbivory. Feeding habits of early dinosaurs have mostly been inferred from qualitative comparisons of dental morphology with extant analogs. Here, we use biomechanical and morphometric methods to investigate the dental morphofunctional diversity of early dinosaurs in comparison with extant squamates and crocodylians and predict their diets using machine learning classification models. Early saurischians/theropods are consistently classified as carnivores. Sauropodomorphs underwent a dietary shift from faunivory to herbivory, experimenting with diverse diets during the Triassic and Early Jurassic, and early ornithischians were likely omnivores. Obligate herbivory was a late evolutionary innovation in both clades. Carnivory is the most plausible ancestral diet of dinosaurs, but omnivory is equally likely under certain phylogenetic scenarios. This early dietary diversity was fundamental in the rise of dinosaurs to ecological dominance.
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Maho T, Maho S, Scott D, Reisz RR. Permian hypercarnivore suggests dental complexity among early amniotes. Nat Commun 2022; 13:4882. [PMID: 35986022 PMCID: PMC9391490 DOI: 10.1038/s41467-022-32621-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 08/09/2022] [Indexed: 11/09/2022] Open
Abstract
AbstractThe oldest known complex terrestrial vertebrate community included hypercarnivorous varanopids, a successful clade of amniotes with wide geographic and temporal distributions. Little is known about their dentition and feeding behaviour, but with the unprecedented number of specimens of the varanopid Mesenosaurus from cave deposits in Oklahoma, we show that it exhibited serrations on the tooth crowns, and exceptionally rapid rates of development and reduced longevity relative to other terrestrial amniotes. In contrast, the coeval large apex predator Dimetrodon greatly increased dental longevity by increasing thickness and massiveness, whereas herbivores greatly reduced tooth replacement rates and increased dental longevity. Insectivores and omnivores represented the primitive condition and maintained modest replacement rates and longevity. The varied patterns of dental development among these early terrestrial amniotes reveal a hidden aspect of dental complexity in the emerging diverse amniote community, very soon after their initial appearance in the fossil record.
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Chang H, You HL, Xu L, Ma W, Gao D, Jia S, Xia M, Zhang J, Li Y, Wang X, Liu D, Li J, Zhang J, Yang L, Wei X. Relatively low tooth replacement rate in a sauropod dinosaur from the Early Cretaceous Ruyang Basin of central China. PeerJ 2021; 9:e12361. [PMID: 34760377 PMCID: PMC8556709 DOI: 10.7717/peerj.12361] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Accepted: 09/30/2021] [Indexed: 11/20/2022] Open
Abstract
Tooth replacement rate is an important feature related to feeding mechanics and food choices for dinosaurs. However, only a few data points are available for sauropod dinosaurs, partially due to rarity of relevant fossil material. Four somphospondylan sauropod species have been recovered from the Lower Cretaceous Aptian–Albian Haoling Formation in the Ruyang Basin, Henan Province of central China, but no cranial material has been reported except for a single crown. Here we report the discovery of the rostral portion of a left dentary with replacement teeth in its first five alveoli. Comparative anatomical study shows the partial dentary can be assigned to a member of early diverging somphospondylans. The non-destructive tooth length-based approach to estimating tooth formation time and replacement rate is adopted here. The estimated tooth replacement rate is 76 days, faster than that of Brachiosaurus (83 days) and much lower than typical late diverging lithostrotian titanosaurians (20 days). Thus, this discovery adds an intermediate tooth replacement rate in the evolution of titanosauriform sauropods and supports the idea that evolution of tooth replacement rate is clade-specific. This discovery also provides more information to understand the Ruyang sauropod assemblage, which includes one of the most giant dinosaurs to have walked our Earth (Ruyangosaurus giganteus).
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Affiliation(s)
- Huali Chang
- Henan Natural History Museum, Zhengzhou, China
| | - Hai-Lu You
- 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
| | - Li Xu
- Henan Natural History Museum, Zhengzhou, China
| | - Waisum Ma
- School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom
| | | | - Songhai Jia
- Henan Natural History Museum, Zhengzhou, China
| | - Mengli Xia
- Henan Natural History Museum, Zhengzhou, China
| | | | - Yu Li
- Henan Natural History Museum, Zhengzhou, China
| | - Xirui Wang
- Henan Natural History Museum, Zhengzhou, China
| | - Di Liu
- Henan Natural History Museum, Zhengzhou, China
| | - Jie Li
- Henan Natural History Museum, Zhengzhou, China
| | | | - Lili Yang
- Henan Natural History Museum, Zhengzhou, China
| | - Xuefang Wei
- Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China
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7
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Melstrom KM, Chiappe LM, Smith ND. Exceptionally simple, rapidly replaced teeth in sauropod dinosaurs demonstrate a novel evolutionary strategy for herbivory in Late Jurassic ecosystems. BMC Ecol Evol 2021; 21:202. [PMID: 34742237 PMCID: PMC8571970 DOI: 10.1186/s12862-021-01932-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Accepted: 10/15/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Dinosaurs dominated terrestrial environments for over 100 million years due in part to innovative feeding strategies. Although a range of dental adaptations was present in Late Jurassic dinosaurs, it is unclear whether dinosaur ecosystems exhibited patterns of tooth disparity and dietary correlation similar to those of modern amniotes, in which carnivores possess simple teeth and herbivores exhibit complex dentitions. To investigate these patterns, we quantified dental shape in Late Jurassic dinosaurs to test relationships between diet and dental complexity. RESULTS Here, we show that Late Jurassic dinosaurs exhibited a disparity of dental complexities on par with those of modern saurians. Theropods possess relatively simple teeth, in spite of the range of morphologies tested, and is consistent with their inferred carnivorous habits. Ornithischians, in contrast, have complex dentitions, corresponding to herbivorous habits. The dentitions of macronarian sauropods are similar to some ornithischians and living herbivorous squamates but slightly more complex than other sauropods. In particular, all diplodocoid sauropods investigated possess remarkably simple teeth. The existence of simple teeth in diplodocoids, however, contrasts with the pattern observed in nearly all known herbivores (living or extinct). CONCLUSIONS Sauropod dinosaurs exhibit a novel approach to herbivory not yet observed in other amniotes. We demonstrate that sauropod tooth complexity is related to tooth replacement rate rather than diet, which contrasts with the results from mammals and saurians. This relationship is unique to the sauropod clade, with ornithischians and theropods displaying the patterns observed in other groups. The decoupling of herbivory and tooth complexity paired with a correlation between complexity and replacement rate demonstrates a novel evolutionary strategy for plant consumption in sauropod dinosaurs.
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Affiliation(s)
- Keegan M Melstrom
- The Dinosaur Institute, Natural History Museum of Los Angeles County, 900 W Exposition Blvd, Los Angeles, CA, USA.
| | - Luis M Chiappe
- The Dinosaur Institute, Natural History Museum of Los Angeles County, 900 W Exposition Blvd, Los Angeles, CA, USA
| | - Nathan D Smith
- The Dinosaur Institute, Natural History Museum of Los Angeles County, 900 W Exposition Blvd, Los Angeles, CA, USA
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8
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Wu YH, Chiappe LM, Bottjer DJ, Nava W, Martinelli AG. Dental replacement in Mesozoic birds: evidence from newly discovered Brazilian enantiornithines. Sci Rep 2021; 11:19349. [PMID: 34593843 PMCID: PMC8484441 DOI: 10.1038/s41598-021-98335-8] [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: 05/10/2021] [Accepted: 08/24/2021] [Indexed: 02/08/2023] Open
Abstract
Polyphyodonty-multiple tooth generations-in Mesozoic birds has been confirmed since the nineteenth century. Their dental cycle had been assessed through sparse data from tooth roots revealed through broken jawbones and disattached teeth. However, detailed descriptions of their tooth cycling are lacking, and the specifics of their replacement patterns remain largely unknown. Here we present unprecedented µCT data from three enantiornithine specimens from the Upper Cretaceous of southeastern Brazil. The high resolution µCT data show an alternating dental replacement pattern in the premaxillae, consistent with the widespread pattern amongst extinct and extant reptiles. The dentary also reveals dental replacement at different stages. These results strongly suggest that an alternating pattern was typical of enantiornithine birds. µCT data show that new teeth start lingually within the alveoli, resorb roots of functional teeth and migrate labially into their pulp cavities at an early stage, similar to modern crocodilians. Our results imply that the control mechanism for tooth cycling is conserved during the transition between non-avian reptiles and birds. These first 3D reconstructions of enantiornithine dental replacement demonstrate that 3D data are essential to understand the evolution and deep homology of archosaurian tooth cycling.
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Affiliation(s)
- Yun-Hsin Wu
- grid.243983.70000 0001 2302 4724Natural History Museum of Los Angeles County, Los Angeles, CA USA ,grid.42505.360000 0001 2156 6853University of Southern California, Los Angeles, CA USA
| | - Luis M. Chiappe
- grid.243983.70000 0001 2302 4724Natural History Museum of Los Angeles County, Los Angeles, CA USA
| | - David J. Bottjer
- grid.42505.360000 0001 2156 6853University of Southern California, Los Angeles, CA USA
| | - William Nava
- Museu de Paleontologia de Marília, Marília, São Paulo, Brazil
| | - Agustín G. Martinelli
- grid.459814.50000 0000 9653 9457Museo Argentino Ciencias Naturales “Bernardino Rivadavia”, Buenos Aires, Argentina
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9
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Hulsey CD, Meyer A, Streelman JT. Convergent Evolution of Cichlid Fish Pharyngeal Jaw Dentitions in Mollusk-Crushing Predators: Comparative X-Ray Computed Tomography of Tooth Sizes, Numbers, and Replacement. Integr Comp Biol 2021; 60:656-664. [PMID: 32584994 DOI: 10.1093/icb/icaa089] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Dental convergence is a hallmark of cichlid fish adaptive radiations. This type of repeated evolution characterizes both the oral jaws of these fishes as well as their pharyngeal jaws that are modified gill arches used to functionally process prey like hard-shelled mollusks. To test several hypotheses regarding the evolution of cichlid crushing pharyngeal dentitions, we used X-ray computed tomography scans to comparatively examine dental evolution in the pharyngeal jaw of a diversity of New World Heroine cichlid lineages. The substantial variation in erupted tooth sizes and numbers as well as replacement teeth found in these fishes showed several general patterns. Larger toothed species tended to have fewer teeth suggesting a potential role of spatial constraints in cichlid dental divergence. Species with larger numbers of erupted pharyngeal teeth also had larger numbers of replacement teeth. Replacement tooth size is almost exactly predicted (r = 0.99) from the size of erupted teeth across all of the species. Mollusk crushing was, therefore, highly associated with not only larger pharyngeal teeth, but also larger replacement teeth. Whether dental divergence arises as a result of environmental induced plasticity or originates via trophic polymorphism as found in the species Herichthys minckleyi, there appear to be general rules that structure interspecific divergence in cichlid pharyngeal erupted and replacement dentitions.
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Affiliation(s)
- C Darrin Hulsey
- Department of Biology, University of Konstanz, Konstanz, Germany
| | - Axel Meyer
- Department of Biology, University of Konstanz, Konstanz, Germany
| | - J Todd Streelman
- School of Biological Sciences, Institute of Technology, Atlanta, GA 30332, USA
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10
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Whitney MR, LeBlanc ARH, Reynolds AR, Brink KS. Convergent dental adaptations in the serrations of hypercarnivorous synapsids and dinosaurs. Biol Lett 2020; 16:20200750. [PMID: 33321067 DOI: 10.1098/rsbl.2020.0750] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Theropod dinosaurs are well known for having a ziphodont dentition: serrated, blade-shaped teeth that they used for cutting through prey. Serrations along the carinae of theropod teeth are composed of true denticles, a complex arrangement of dentine, enamel, and interdental folds. This structure would have supported individual denticles and dissipated the stresses associated with feeding. These particular serrations were previously thought to be unique to theropod dinosaurs and some other archosaurs. Here, we identify the same denticles and interdental folds forming the cutting edges in the teeth of a Permian gorgonopsian synapsid, extending the temporal and phylogenetic distribution of this dental morphology. This remarkable instance of convergence not only represents the earliest record of this adaptation to hypercarnivory but also demonstrates that the first iteration of this feature appeared in non-mammalian synapsids. Comparisons of tooth serrations in gorgonopsians with those of earlier synapsids and hypercarnivorous mammals reveal some gorgonopsians acquired a complex tissue arrangement that differed from other synapsids.
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Affiliation(s)
- M R Whitney
- Museum of Comparative Zoology, Harvard University, Cambridge, MA 02138, USA
| | - A R H LeBlanc
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9
| | - A R Reynolds
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada M5S 3B2
| | - K S Brink
- Department of Geological Sciences, University of Manitoba, 125 Dysart Road, Winnipeg, Manitoba, Canada R3T 2N2
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11
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Kosch JCD, Zanno LE. Sampling impacts the assessment of tooth growth and replacement rates in archosaurs: implications for paleontological studies. PeerJ 2020; 8:e9918. [PMID: 32999766 PMCID: PMC7505082 DOI: 10.7717/peerj.9918] [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: 04/03/2020] [Accepted: 08/20/2020] [Indexed: 11/20/2022] Open
Abstract
Dietary habits in extinct species cannot be directly observed; thus, in the absence of extraordinary evidence, they must be reconstructed with a combination of morphological proxies. Such proxies often include information on dental organization and function such as tooth formation time and tooth replacement rate. In extinct organisms, tooth formation times and tooth replacement rate are calculated, in part via extrapolation of the space between incremental lines in dental tissues representing daily growth (von Ebner Line Increment Width; VEIW). However, to date, little work has been conducted testing assumptions about the primary data underpinning these calculations, specifically, the potential impact of differential sampling and data extrapolation protocols. To address this, we tested a variety of intradental, intramandibular, and ontogentic sampling effects on calculations of mean VEIW, tooth formation times, and replacement rates using histological sections and CT reconstructions of a growth series of three specimens of the extant archosaurian Alligator mississippiensis. We find transect position within the tooth and transect orientation with respect to von Ebner lines to have the greatest impact on calculations of mean VEIW—a maximum number of VEIW measurements should be made as near to the central axis (CA) as possible. Measuring in regions away from the central axis can reduce mean VEIW by up to 36%, causing inflated calculations of tooth formation time. We find little demonstrable impact to calculations of mean VEIW from the practice of subsampling along a transect, or from using mean VEIW derived from one portion of the dentition to extrapolate for other regions of the dentition. Subsampling along transects contributes only minor variations in mean VEIW (<12%) that are dwarfed by the standard deviation (SD). Moreover, variation in VEIW with distance from the pulp cavity likely reflects idiosyncratic patterns related to life history, which are difficult to control for; however, we recommend increasing the number of VEIW measured to minimize this effect. Our data reveal only a weak correlation between mean VEIW and body length, suggesting minimal ontogenetic impacts. Finally, we provide a relative SD of mean VEIW for Alligator of 29.94%, which can be used by researchers to create data-driven error bars for tooth formation times and replacement rates in fossil taxa with small sample sizes. We caution that small differences in mean VEIW calculations resulting from non-standardized sampling protocols, especially in a comparative context, will produce inflated error in tooth formation time estimations that intensify with crown height. The same holds true for applications of our relative SD to calculations of tooth formation time in extinct taxa, which produce highly variable maximum and minimum estimates in large-toothed taxa (e.g., 718–1,331 days in Tyrannosaurus).
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Affiliation(s)
- Jens C D Kosch
- Paleontology, North Carolina Museum of Natural Sciences, Raleigh, NC, USA.,Department of Biological Sciences, North Carolina State University, Raleigh, NC, USA
| | - Lindsay E Zanno
- Paleontology, North Carolina Museum of Natural Sciences, Raleigh, NC, USA.,Department of Biological Sciences, North Carolina State University, Raleigh, NC, USA
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12
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Jenkins KM, Shaw JO. Bite force data suggests relationship between acrodont tooth implantation and strong bite force. PeerJ 2020; 8:e9468. [PMID: 32656000 PMCID: PMC7333653 DOI: 10.7717/peerj.9468] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 06/11/2020] [Indexed: 12/22/2022] Open
Abstract
Extant and extinct reptiles exhibit numerous combinations of tooth implantation and attachment. Tooth implantation ranges from those possessing roots and lying within a socket (thecodonty), to teeth lying against the lingual wall of the jawbone (pleurodonty), to teeth without roots or sockets that are attached to the apex of the marginal jawbones (acrodonty). Attachment may be ligamentous (gomphosis) or via fusion (ankylosis). Generally speaking, adaptative reasonings are proposed as an underlying driver for evolutionary changes in some forms of tooth implantation and attachment. However, a substantiated adaptive hypothesis is lacking for the state of acrodont ankylosis that is seen in several lineages of Lepidosauria, a clade that is plesiomorphically pleurodont. The convergent evolution of acrodont ankylosis in several clades of lepidosaurs suggests a selective pressure shaped the evolution of the trait. We hypothesize that acrodont ankylosis as seen in Acrodonta and Sphenodon punctatus, is an adaptation either resulting from or allowing for a stronger bite force. We analyzed bite force data gathered from the literature to show that those taxa possessing acrodont dentition possess a stronger bite force on average than those taxa with pleurodont dentition. Dietary specialists with pleurodont dentition may also possess relatively high bite forces, though body size may also play a role in their ability to bite hard. Furthermore, our results have implications for the evolution of acrodont ankylosis and potential behaviors related to strong bite force that influenced the evolution of acrodonty within Acrodonta and Rhynchocephalia.
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Affiliation(s)
- Kelsey M Jenkins
- Department of Earth and Planetary Sciences, Yale University, New Haven, United States of America
| | - Jack O Shaw
- Department of Earth and Planetary Sciences, Yale University, New Haven, United States of America
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13
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D'Emic MD, O'Connor PM, Pascucci TR, Gavras JN, Mardakhayava E, Lund EK. Correction: Evolution of high tooth replacement rates in theropod dinosaurs. PLoS One 2019; 14:e0226897. [PMID: 31877186 PMCID: PMC6932751 DOI: 10.1371/journal.pone.0226897] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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