Biology of tooth replacement in amniotes

Whitlock, John A.; Richman, Joy M.

doi:10.1038/ijos.2013.36

Cited by 66 publications

(52 citation statements)

References 49 publications

(65 reference statements)

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“…These waves of replacement, first described by Woerdeman (1921), are known as Zahnreihen and are a phenomenon that has been confirmed subsequently (in adult specimens at least) for fossil and extant taxa by several authors (e.g. Edmund, 1960Edmund, , 1969Hopson, 1980;DeMar & Bolt, 1981;de Ricql es & Bolt, 1983;Kieser et al 1993;Small, 1997;Delgado et al 2003), but see a review by Whitlock & Richman (2013) for other hypotheses. In most reptiles, replacement teeth develop directly lingually to the corresponding functional teeth and lie in resorption pits at the bases of the latter, whereupon the attachment is resorbed, the functional tooth is lost and the replacement tooth takes its place.…”

Section: Tooth Replacement In Reptilesmentioning

confidence: 89%

Unique method of tooth replacement in durophagous placodont marine reptiles, with new data on the dentition of Chinese taxa

Neenan

Rieppel

et al. 2014

Journal of Anatomy

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The placodonts of the Triassic period (~252-201 mya) represent one of the earliest and most extreme specialisations to a durophagous diet of any known reptile group. Exceptionally enlarged crushing tooth plates on the maxilla, dentary and palatine cooperated to form functional crushing areas in the buccal cavity. However, the extreme size of these teeth, combined with the unusual way they occluded, constrained how replacement occurred. Using an extensive micro-computed tomographic dataset of 11 specimens that span all geographic regions and placodont morphotypes, tooth replacement patterns were investigated. In addition, the previously undescribed dental morphologies and formulae of Chinese taxa are described for the first time and incorporated into the analysis. Placodonts have a unique tooth replacement pattern and results follow a phylogenetic trend. The plesiomorphic Placodus species show many replacement teeth at various stages of growth, with little or no discernible pattern. On the other hand, the more derived cyamodontoids tend to have fewer replacement teeth growing at any one time, replacing teeth unilaterally and/or in functional units, thus maintaining at least one functional crushing area at all times. The highly derived placochelyids have fewer teeth and, as a result, only have one or two replacement teeth in the upper jaw. This supports previous suggestions that these taxa had an alternative diet to other placodonts. Importantly, all specimens show at least one replacement tooth growing at the most posterior palatine tooth plates, indicating increased wear at this point and thus the most efficient functional crushing area.

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Section: Tooth Replacement In Reptilesmentioning

confidence: 89%

Unique method of tooth replacement in durophagous placodont marine reptiles, with new data on the dentition of Chinese taxa

Neenan

Rieppel

et al. 2014

Journal of Anatomy

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“…Whitlock & Richman () reviewed tooth replacement mechanisms. The dental lamina plays a key role in this process (Järvinen et al.…”

Section: Discussionmentioning

confidence: 99%

“…The pattern of implantation of baleen plates, accessory plates and bristles on the back of the palate has no match in mammals, but is reminiscent of other ectodermal structures in the mouth of other vertebrates. Generations of replacement teeth in reptiles, for instance, are arranged in patterns that show a maturation gradient from medial to lateral, but implantation of individual elements in rows that are oblique to the mediolateral plane (Westergaard & Ferguson, ; Whitlock & Richman, ).…”

Section: Discussionmentioning

confidence: 99%

Evolutionary aspects of the development of teeth and baleen in the bowhead whale

et al. 2017

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In utero, baleen whales initiate the development of several dozens of teeth in upper and lower jaws. These tooth germs reach the bell stage and are sometimes mineralized, but toward the end of prenatal life they are resorbed and no trace remains after birth. Around the time that the germs disappear, the keratinous baleen plates start to form in the upper jaw, and these form the food-collecting mechanism. Baleen whale ancestors had two generations of teeth and never developed baleen, and the prenatal teeth of modern fetuses are usually interpreted as an evolutionary leftover. We investigated the development of teeth and baleen in bowhead whale fetuses using histological and immunohistochemical evidence. We found that upper and lower dentition initially follow similar developmental pathways. As development proceeds, upper and lower tooth germs diverge developmentally. Lower tooth germs differ along the length of the jaw, reminiscent of a heterodont dentition of cetacean ancestors, and lingual processes of the dental lamina represent initiation of tooth bud formation of replacement teeth. Upper tooth germs remain homodont and there is no evidence of a secondary dentition. After these germs disappear, the oral epithelium thickens to form the baleen plates, and the protein FGF-4 displays a signaling pattern reminiscent of baleen plates. In laboratory mammals, FGF-4 is not involved in the formation of hair or palatal rugae, but it is involved in tooth development. This leads us to propose that the signaling cascade that forms teeth in most mammals has been exapted to be involved in baleen plate ontogeny in mysticetes.

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“…Teeth are constantly replaced in most non‐mammalian gnathostomes (i.e., polyphyodonty) (Whitlock and Richman, ). Previous studies such as Edmund (, , ) have confirmed that the tooth replacement in diapsid reptiles is a well‐controlled phenomenon that produces a regular pattern in a single dentition including unerupted replacement teeth (Fig.…”

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Description of Tooth Ontogeny and Replacement Patterns in a Juvenile Tarbosaurus bataar (Dinosauria: Theropoda) Using CT‐Scan Data

Hanai

Tsuihiji

2018

The Anatomical Record

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Teeth are continually replaced in most of non‐mammalian gnathostomes to maintain their functional dentitions. To clarify the tooth replacement patterns in tyrannosaurid theropod dinosaurs, we examined well‐preserved dentitions (both premaxillae, left maxilla, partial right maxilla, and both dentaries) of a juvenile Tarbosaurus bataar (MPC‐D 107/7) using X‐ray computed tomographic (CT) imaging. Three‐dimensional (3D) rendering of the dentitions and staging of replacement teeth allowed quantitative analyses of the tooth ontogeny and replacement patterns in this specimen. These strategies were validated by comparing the results between MPC‐D 107/7 and extant crocodilians, which are taxa that have previously been studied using non‐CT methods. 3D‐rendered dentitions of MPC‐D 107/7 showed alternate replacement patterns between odd‐ and even‐numbered alveoli. Such patterns were discontinuous at the premaxilla‐maxilla junctions, suggesting the division of replacement patterns between the two dentitions possessing morpho‐functionally different features. The replacement process in the odd‐numbered alveoli of the left maxilla sequentially proceeded from distal alveoli. Meanwhile, in the both dentaries, there were simple alternate patterns in which functional teeth would be simultaneously shed out in every second alveoli. Such a simple alternation had never been reported in the adult tyrannosaurid dentaries. Under this pattern, the half of functional teeth in a single dentition would be shed at the same time, which may hamper foraging functions. We conclude that the simple alternate patterns found in the dentary dentitions of MPC‐D 107/7 represent transient condition in juvenile tyrannosaurids, suggesting ontogenetic changes in tooth replacement patterns in the tyrannosaurid dentary. Anat Rec, 302:1210–1225, 2019. © 2018 Wiley Periodicals, Inc.

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Biology of tooth replacement in amniotes

Cited by 66 publications

References 49 publications

Unique method of tooth replacement in durophagous placodont marine reptiles, with new data on the dentition of Chinese taxa

Unique method of tooth replacement in durophagous placodont marine reptiles, with new data on the dentition of Chinese taxa

Evolutionary aspects of the development of teeth and baleen in the bowhead whale

Description of Tooth Ontogeny and Replacement Patterns in a Juvenile Tarbosaurus bataar (Dinosauria: Theropoda) Using CT‐Scan Data

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