Teeth and taxonomy in ankylosaurs

Coombs, Walter P.

doi:10.1017/cbo9780511608377.023

Cited by 50 publications

(38 citation statements)

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“…Nevertheless, naming isolated herbivore-like teeth can be hazardous because future work may show that separate species possess identical dental morphologies (e.g. Lambe 1918;Coombs 1990).…”

Section: Discussionmentioning

confidence: 99%

The Late Triassic pseudosuchian Revueltosaurus callenderi and its implications for the diversity of early ornithischian dinosaurs

Parker¹,

et al. 2005

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A new discovery of skeletons of Revueltosaurus callenderi from the Upper Triassic Chinle Formation of Petrified Forest National Park, Arizona clearly shows that Revueltosaurus is not an ornithischian dinosaur as previously supposed. Features such as the presence of a postfrontal, crocodile-normal ankle and paramedian osteoderms with anterior bars place R. callenderi within the Pseudosuchia, closer to crocodylomorphs than to dinosaurs. Therefore, dental characters previously used to place Revueltosaurus within the Ornithischia evolved convergently among other archosaur taxa, and cannot be used to diagnose ornithischian dinosaur teeth. As a result, all other putative North American Late Triassic ornithischians, which are all based exclusively on teeth, are cast into doubt. The only reasonably well-confirmed Late Triassic ornithischians worldwide are Pisanosaurus mertii and an unnamed heterodontosaurid from Argentina. This considerably changes the understanding of early dinosaur diversity, distribution and evolution in the Late Triassic.

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“…Nevertheless, naming isolated herbivore-like teeth can be hazardous because future work may show that separate species possess identical dental morphologies (e.g. Lambe 1918;Coombs 1990).…”

Section: Discussionmentioning

confidence: 99%

The Late Triassic pseudosuchian Revueltosaurus callenderi and its implications for the diversity of early ornithischian dinosaurs

Parker¹,

et al. 2005

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“…In addition, the identification of some of the previously examined teeth, such as those of Velociraptor and Tarbosaurus by Dauphin (1988Dauphin ( , 1989, is dubious; these teeth were described as isolated finds, so they cannot be confidently attributed to taxa at the generic level (Dauphin et al, 1989). To make matters even worse, some of the taxa, such as "Paronychodon" (Cope, 1876) and "Palaeoscincus" (Leidy, 1856), are nomina dubia erected on the basis of isolated teeth (Coombs, 1990;Currie et al, 1990). Sampling on a finer scale is not useful if the specimens studied cannot also be identified to a finer level, i.e., to the genus or species.…”

mentioning

confidence: 99%

Phylogenetic patterns of enamel microstructure in dinosaur teeth

Hwang

2005

Journal of Morphology

156

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The tooth enamel microstructure of all the dinosaur taxa that are adequately represented in the American Museum of Natural History collections were analyzed using scanning electron microscopy. This study aims to determine whether or not better sampling within a major nonmammalian amniote (hereafter referred to descriptively as "reptile") clade will unearth phylogenetic patterns in enamel microstructure in addition to those dictated by tooth function. While interest in reptile enamel microstructure has increased in the past few years, intensive sampling focused on just one monophyletic reptile clade was not previously implemented. This study reveals that phylogenetic constraints play a larger role in shaping enamel microstructure in reptiles than previously thought. Within many monophyletic dinosaur clades the combination of enamel types and enamel features within a tooth-the schmelzmuster-is the same in all the taxa due to their common ancestry, and their schmelzmusters are diagnostic of their respective clades. While distantly related taxa with similar teeth and diets have similar schmelzmusters due to functional constraints, phylogenetic constraints keep those schmelzmusters distinct from one another. An interesting finding of this analysis is that the enamel complexity of a taxon does not necessarily coincide with the position of the taxon on a phylogenetic tree; more derived taxa do not necessarily have more derived enamel and more primitive taxa do not necessarily have more primitive enamel.

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“…1b in CHE02.084). The mesiodistal asymmetry of the crown mentioned by Galton (1990) or Galton and Upchurch (2004), with a convex mesial outline bearing fewer and/or larger marginal denticles (contrary to what is observed in ankylosaurs by Coombs 1990), and a slightly concave distal outline with smaller denticles, is unclear here. Even though some denticles are broken or worn, the mesial and distal outlines seem quite symmetrical, convex, with similar marginal denticles in terms of number and size.…”

Section: Affinities Amongst Stegosauriamentioning

confidence: 56%

“…Stegosaurus and Hesperosaurus; difference between LHNB(CN)-1-01 and other known Stegosaurus). In the same way, Coombs (1990) has observed a high variability of this character in ankylosaurs, even in a single individual. Thus b Magnified lateral view of the left jaw, with very well-preserved teeth, including several maxillary teeth still in original position, and possibly some displaced dentary teeth in the posterior part.…”

Section: Affinities Amongst Stegosauriamentioning

confidence: 59%

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A stegosaur tooth (Dinosauria, Ornithischia) from the Early Cretaceous of southwestern France

Billon‐Bruyat¹,

Mazin

Pouech

2010

Swiss J Geosci

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International audienceThe spotty nature of the terrestrial fossil record for the Mesozoic hinders a more complete understanding of dinosaur diversity. For stegosaurs (Ornithischia), the plated dinosaurs, only a few and fragmentary remains are reported from the Early Cretaceous of Europe. A recent revision concluded that only a partial vertebra of the nomen dubium Craterosaurus (?Aptian, England) could be considered as stegosaurian. Here we report on a stegosaur tooth from the Early Cretaceous (Berriasian) Purbeckian deposits of Cherves-de-Cognac (Charente), southwestern France. This tiny tooth was examined in detail using microtomography. Comparisons being limited by the rarity of stegosaur tooth rows material (e.g., from the skull of the holotype of Stegosaurus stenops) and dental material, notably from Europe, we observed new material of cf. Stegosaurus armatus and Hesperosaurus mjosi from the Upper Jurassic Morrison Formation of Wyoming (USA). The tooth shows the most similarities to the Late Jurassic genera Stegosaurus and Hesperosaurus, but differs in having a distinctive downwardly arched (V-shaped) cingulum on the ?lingual face (maxillary tooth hypothesis). It is referred to as Stegosauria indeterminate, a medium-sized quadrupedal herbivore that inhabited an emerged land between the Armorican Massif and the Massif Central. This finding is the first evidence of a stegosaur from the Early Cretaceous of France and a welcome addition to the meagre European record of that time. In addition, it is the second stegosaurian tooth crown reported from Europe. The assemblage of ornithischians of Cherves-de-Cognac shares some similarities with that of the Early Cretaceous (Berriasian) of the Purbeck Limestone Group, southern England. The relative rarity of ornithischian osteological remains in both Purbeckian environments suggests that most of these dinosaurs were mainly inhabitants of inland terrestrial palaeoenvironments

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Teeth and taxonomy in ankylosaurs

Cited by 50 publications

References 0 publications

The Late Triassic pseudosuchian Revueltosaurus callenderi and its implications for the diversity of early ornithischian dinosaurs

The Late Triassic pseudosuchian Revueltosaurus callenderi and its implications for the diversity of early ornithischian dinosaurs

Phylogenetic patterns of enamel microstructure in dinosaur teeth

A stegosaur tooth (Dinosauria, Ornithischia) from the Early Cretaceous of southwestern France

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