Ford 1997 Did theropods have lizard lips

Palaeontologia Electronica, 2019

Dataset Clade t-test, ci t-test, ri M-W, ci M-W, ri Brusatte et al. (2014) Non-avian Coelurosauria 2.14E-10 4.67E-14 6.77E-10 2.26E-15 Carrano et al. (2012) Non-coelurosaur Tetanurae 2.29E-09 5.42E-13 4.61E-10 1.03E-12 Choiniere et al. (2014a) Non-avian Theropoda 0.22025 7.31E-07 0.4483 2.01E-07 Foth and Rauhut (2017) Non-avian Coelurosauria 0

The Anatomical Record Part A: Discoveries in Molecular, Cellular, and Evolutionary Biology, 2005

Isolated theropod teeth are common Mesozoic fossils and would be an important data source for paleoecology biogeography if they could be reliably identified as having come from particular taxa. However, obtaining identifications is confounded by a paucity of easily identifiable characters. Here we discuss a quantitative methodology designed to provide defensible identifications of isolated teeth using Tyrannosaurus as a comparison taxon. We created a standard data set based as much as possible on teeth of known taxonomic affinity against which to compare isolated crowns. Tooth morphology was described using measured variables describing crown length, base length and width, and derived variables related to basal shape, squatness, mesial curve shape, apex location with respect to base, and denticle size. Crown curves were described by fitting the power function Y ϭ a ϩ bX 0.5 to coordinate data collected from lateral-view images of mesial curve profiles. The b value from these analyses provides a measure of curvature. Discriminant analyses compared isolated teeth of various taxonomic affinities against the standard. The analyses classified known Tyrannosaurus teeth with Tyrannosaurus and separated most teeth known not to be Tyrannosaurus from Tyrannosaurus. They had trouble correctly classifying teeth that were very similar to Tyrannosaurus and for which there were few data in the standard. However, the results indicate that expanding the standard should facilitate the identification of numerous types of isolated theropod teeth. 2005 Wiley-Liss, Inc.

Academia Letters, 2021

Most vertebrates, both extinct and extant, have lips or any kind of extraoral tissue that works to seal the mouth when closed or to cover/protect the teeth if these are present. All modern and extinct amphibians, living lizards and snakes and most of the extinct diapsids have them (Gregory S. Paul, The Prehistoric Times Magazine 2018 [from now on Paul, 2018]). When do we have liplessness, then? Mainly, only three conditions make the animal lack this extraoral tissue: a) The teeth are too long. b) The teeth project outside the line of the jaw and/or interlock with each other. c) For functional, behavioural reasons. Piscivorous habits, mainly. (Paul, 2018) Examples for a) are: babirusas, elephants and other proboscideans, walruses, musk deers or, probably, sabre-toothed cats. These last ones have their extant similar counterpart in Neofelis nebulosa, which, if known only from fossils, would probably be restored with slightly exposed canines, Mark Witton suggests in his blog post from October 2016. Although it is generally accepted that many of those extinct cats had too long canines to be covered. To sum up, of course all these animals have lips, only that these lips can't cover their larger teeth. Examples for b) are: crocodilians, toothed pterosaurs or abyssal fish. Examples for c) are: phytosaurs, Dilophosaurus (partially, only in the frontal part of their jaws, see Fig. 1), spinosaurids (partially, only in the frontal part of their jaws) and the examples from b).

Acta Palaeontologica Polonica, 2014

Theropod teeth are particularly abundant in the fossil record and frequently reported in the literature. Yet, the dentition of many theropods has not been described comprehensively, omitting details on the denticle shape, crown ornamentations and enamel texture. This paucity of information has been particularly striking in basal clades, thus making identification of isolated teeth difficult, and taxonomic assignments uncertain. We here provide a detailed description of the dentition of Megalosauridae, and a comparison to and distinction from superficially similar teeth of all major theropod clades. Megalosaurid dinosaurs are characterized by a mesial carina facing mesiolabially in mesial teeth, centrally positioned carinae on both mesial and lateral crowns, a mesial carina terminating above the cervix, and short to well-developed interdenticular sulci between distal denticles. A discriminant analysis performed on a dataset of numerical data collected on the teeth of 62 theropod taxa reveals that megalosaurid teeth are hardly distinguishable from other theropod clades with ziphodont dentition. This study highlights the importance of detailing anatomical descriptions and providing additional morphometric data on teeth with the purpose of helping to identify isolated theropod teeth in the future.

Journal of Vertebrate Paleontology, 2007

Geology Today, 2001

Journal of Vertebrate Paleontology, 2000

The teeth of lizards are generally considered to be structurally simple, especially when compared to the complex dentitions of mammals. This simplicity in tooth morphology underscores the relatively simple feeding processes of lizards as opposed to the complex mastication processes in mammals . Described herein are new specimens of the Late Cretaceous lizard Peneteius aquilonius. These teeth and jaw fragments show many specializations similar to those found in the molars of tribosphenic mammals. Most notably, the posterior teeth of Peneteius aquilonius are molariform and the upper teeth are shaped quite differently than the lower teeth. These dental specializations provided Peneteius aquilonius with a mechanism for efficient oral food processing. Unlike some crocodilians with ''mammal-like'' teeth (Clark et al., 1989; in which food was processed by proal movement of the lower jaw, Peneteius aquilonius appears to have processed food by cutting and crushing in a manner similar to that of an insectivorous mammal.

The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology, 2009

The serrated, or denticulated, ziphodont teeth of theropod dinosaurs display variability in their extent of denticulation. The functional model proposed here tests the hypothesis that denticles will not exist in areas that do not frequently contact the substrate. This area, defined as the ''dead-space,'' is determined by the direction the tooth moves through the fleshy substrate. The extent of denticulation, as well as the dead-space dimensions, is measured from photographs of 235 isolated and in situ theropod teeth, to determine a meaningful relationship between the two variables. Both Euclidean and geometric morphometric methods are employed, and the data are expressed in bivariate and ordination plots. The model predicts the direction of tooth movement through the curvature of the tip/apex. Tooth position and taxon are considered. The results show that the mesial margin is usually partially denticulated, while the distal margin is usually totally denticulated. Curved teeth have large dead-spaces, and tend to be less denticulated mesially. Straighter teeth are more extensively denticulated, to the point where they became symmetrical. The mesial denticulation is determined by the dead-space, and dictated by the substrate contact. The dead-space almost always predicted less extensive denticulation; a consequence of the model's limitations. Tooth curvature increases with a more distal position, due to rotation based on the proximity to the hinge. Denticulation indicates that theropods used a distally oriented puncture to modify the substrate, similar to modern analogues. Although there is little taxonomic variation, Troodontidae show unique and extreme degrees of mesial denticulation. Anat Rec, 292:1297Rec, 292: -1314Rec, 292: , 2009. V V C 2009 Wiley-Liss, Inc.

Theropod teeth are typically not described in detail, yet these abundant vertebrate fossils are not only frequently reported in the literature, but also preserve extensive anatomical information. Often in descriptions, important characters of the crown and ornamentations are omitted, and in many instances, authors do not include a description of theropod dentition at all. The paucity of information makes identification of isolated teeth difficult and taxonomic assignments uncertain. Therefore, we here propose a standardization of the anatomical and morphometric terms for tooth anatomical subunits, as well as a methodology to describe isolated teeth comprehensively. As a corollary, this study exposes the importance of detailed anatomical descriptions with the utilitarian purpose of clarifying taxonomy and identifying isolated theropod teeth.

PeerJ, 2017

Previous investigations document functional and phylogenetic signals in the histology of dinosaur teeth. In particular, incremental lines in dentin have been used to determine tooth growth and replacement rates in several dinosaurian clades. However, to date, few studies have investigated the dental microstructure of theropods in the omnivory/her-bivory spectrum. Here we examine dental histology of Therizinosauria, a clade of large-bodied theropods bearing significant morphological evidence for herbivory, by examining the teeth of the early-diverging therizinosaurian Falcarius utahensis, and an isolated tooth referred to Suzhousaurus megatherioides, a highly specialized large-bodied representative. Despite attaining some of the largest body masses among maniraptoran theropod dinosaurs, therizinosaurian teeth are diminutive, measuring no more than 0.90 cm in crown height (CH) and 0.38 cm in crown base length (CBL). Comparisons with other theropods and non-theropodan herbivorous dinosaurs reveals that when controlling for estimated body mass, crown volume in therizinosaurians plots most closely with dinosaurs of similar dietary strategy as opposed to phylogenetic heritage. Analysis of incremental growth lines in dentin, observed in thin sections of therizinosaurian teeth, demonstrates that tooth growth rates fall within the range of other archosaurs, conforming to hypothesized physiological limitations on the production of dental tissues. Despite dietary differences between therizinosaurians and hypercarnivorous theropods, the types of enamel crystallites present and their spatial distribution—i.e., the schmelzmuster of both taxa—is limited to parallel enamel crystal-lites, the simplest form of enamel and the plesiomorphic condition for Theropoda. This finding supports previous hypotheses that dental microstructure is strongly influenced by phylogeny, yet equally supports suggestions of reduced reliance on oral processing in omnivorous/herbivorous theropods rather than the microstructural specializations to diet exhibited by non-theropodan herbivorous dinosaurs. Finally, although our sample is limited, we document a significant reduction in the rate of enamel apposition contrasted with increased relative enamel thickness between early and later diverging therizinosaurians that coincides with anatomical evidence for increased specializations to herbivory in the clade. How to cite this article Button et al. (2017), Incremental growth of therizinosaurian dental tissues: implications for dietary transitions in Theropoda. PeerJ 5:e4129; DOI 10.7717/peerj.4129