Aestivation among ornithopod dinosaurs of the African Trias

Thulborn, Richard A.

doi:10.1111/j.1502-3931.1978.tb01226.x

Cited by 18 publications

(45 citation statements)

References 33 publications

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“…In sum, there is no evidence in favor of periodic complete replacement of the cheek teeth in heterodontosaurids (contra Thulborn 1978). Neither is there solid evidence for "episodic" rather than continuous tooth replacement in Heterodontosaurus during growth (contra Norman et al 2011: 182).…”

Section: Tooth Replacementmentioning

confidence: 98%

“…33). Thulborn (1974: 159) stated there is no evidence of active tooth replacement in Abrictosaurus, suggesting that the entire maxillary and dentary tooth rows were replaced simultaneously during aestivation (Thulborn 1978). The evidence from the dentition does not support this scenario.…”

Section: Abrictosaurus Consorsmentioning

confidence: 99%

“…Thulborn's (1978) "aestivation" hypothesis outlined a life history scenario for heterodontosaurids in which tooth replacement occurred during a seasonal dry season when vegetation was scarce. During the remainder of the year, in this view, tooth eruption was suppressed, allowing newly erupted crowns in cheek tooth rows to develop contiguous wear facets as an integral functional unit.…”

Section: Tooth Replacementmentioning

confidence: 99%

“…Thulborn (1974Thulborn ( , 1978 argued for propalinal jaw movement, basing this argument loosely on the perceived need to maintain "continuous" wear surfaces in cheek tooth rows. Hopson (1980), to the con-trary, argued that wear facets in Lycorhinus and Heterodontosaurus are not continuous and that the disposition of the wear facets is incompatible with propalinal movement.…”

Section: )mentioning

confidence: 99%

“…The reduced caniniform teeth of Abrictosaurus consors, another early and important heterodontosaurid discovery (Thulborn (1974), drew attention to the possibility of sexual dimorphism in the caniniform dentition and possible use of these teeth in agonistic and defensive behavior (Thulborn 1974;Molnar 1977). The aberrant style of tooth replacement in heterodontosaurids (no replacement foramina, possible cessation of replacement with age) and evidence of extensive tooth-to-tooth wear, however, served to underscore the interpretation of heterodontosaurids as specialized herbivores (Thulborn 1974(Thulborn , 1978.…”

Section: Inferred Dietmentioning

confidence: 99%

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Taxonomy, morphology, masticatory function and phylogeny of heterodontosaurid dinosaurs

Sereno

2012

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Heterodontosaurids comprise an important early radiation of small-bodied herbivores that persisted for approximately 100 My from Late Triassic to Early Cretaceous time. Review of available fossils unequivocally establishes Echinodon as a very small-bodied, late-surviving northern heterodontosaurid similar to the other northern genera Fruitadens and Tianyulong. Tianyulong from northern China has unusual skeletal proportions, including a relatively large skull, short forelimb, and long manual digit II. The southern African heterodontosaurid genus Lycorhinus is established as valid, and a new taxon from the same formation is named Pegomastax africanus gen. n., sp. n. Tooth replacement and tooth-to-tooth wear is more common than previously thought among heterodontosaurids, and in Heterodontosaurus the angle of tooth-to-tooth shear is shown to increase markedly during maturation. Long-axis rotation of the lower jaw during occlusion is identified here as the most likely functional mechanism underlying marked tooth wear in mature specimens of Heterodontosaurus. Extensive tooth wear and other evidence suggests that all heterodontosaurids were predominantly or exclusively herbivores. Basal genera such as Echinodon, Fruitadens and Tianyulong with primitive, subtriangular crowns currently are known only from northern landmasses. All other genera except the enigmatic Pisanosaurus have deeper crown proportions and currently are known only from southern landmasses.

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Section: Tooth Replacementmentioning

confidence: 98%

Section: Abrictosaurus Consorsmentioning

confidence: 99%

Section: Tooth Replacementmentioning

confidence: 99%

Section: )mentioning

confidence: 99%

Section: Inferred Dietmentioning

confidence: 99%

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Taxonomy, morphology, masticatory function and phylogeny of heterodontosaurid dinosaurs

Sereno

2012

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Tooth replacement in Manidens condorensis: baseline study to address the replacement pattern in dentitions of early ornithischians

Becerra

Pol

Whitlock

et al. 2020

Papers in Palaeontology

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Dental replacement in Heterodontosauridae has been debated over the last five decades primarily on indirect evidence, such as the development of wear facets and the position of erupted teeth. Direct observation of unerupted teeth provides unambiguous data for understanding tooth replacement but this has been done only for Heterodontosaurus and Fruitadens. This study addresses dental replacement in Manidens condorensis based on the positioning of functional and replacement teeth using microcomputed tomography data, differential wear along the dentition and the differences in labiolingual/apicobasal level of functional teeth. Dental replacement in Manidens condorensis was continuous in an anterior‐to‐posterior wave pattern, with asynchronous tooth eruption and the addition of new teeth posteriorly to the toothrow during ontogeny. Manidens shows the first evidence of dental replacement for the large dentary caniniform in Heterodontosauridae, which possibly had replacement timing distinct from the cheek dentition. Newly erupted teeth imbricate in a mesial cavity–distal crown base relationship during eruption, so that imbrication of the midposterior dentition remains unaltered during tooth replacement. The presence/absence of a small caniniform tooth in the D3 position of several specimens suggests possible intraspecific dimorphism in Manidens. On longitudinal sections of isolated crowns the histological features such as Howship's lacunae and odontoclast spaces are similar in size to extant reptiles. The differential wear decreasing posteriorly and hypothetical Z‐spacing below 2.3 in Manidens are similar to basal ornithischians. Tooth replacement in Heterodontosauridae (and other early ornithischians) provides key information for understanding the dynamics of jaw function and craniomandibular specialization to herbivory.

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