Theropod teeth from the Lower Cretaceous Ilek Formation of Western Siberia, Russia (original) (raw)
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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.
Canadian Journal of Earth Sciences, 2013
Upper Cretaceous (Cenomanian-Turonian) formations in the Kyzylkum Desert of Uzbekistan, especially the Bissekty Formation at Dzharakuduk, have yielded a great diversity of continental vertebrates, including dinosaurs. Underwater screening of the sandy matrix has recovered many dinosaurian teeth. Here we describe and illustrate two types of enigmatic theropod teeth that are referable to Paronychodon and Richardoestesia, respectively. Both of these tooth taxa are well known from the Late Cretaceous of North America and possibly represent stages in the development of the teeth of various paravian theropods. Confirmation of this hypothesis awaits discovery of more complete jaws.
A proposed terminology of theropod teeth (Dinosauria, Saurischia)
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.
Journal of Vertebrate Paleontology, 2019
Richardoestesia is an enigmatic theropod dinosaur originally described on the basis of a pair of dentaries (holotype of R. gilmorei Currie et al., 1990) and isolated distinctive teeth, which are abundant in the Upper Cretaceous of North America. Richardoestesia asiatica (Nesov, 1995) is represented by numerous isolated teeth from the Upper Cretaceous Khodzhakul, Bissekty, and Aitym formations of Uzbekistan. Richardoestesia asiatica shows the typical features of the genus, including small mesial and distal denticles (on average 28.4 and 34.5 denticles per 5 mm, respectively), rectangular or knob-like denticles, and an apically convex distal margin of the tooth crown. The sample of R. asiatica has a large proportion of straight teeth (morphotype A) and includes several types of recurved teeth related to their position in the jaws (morphotypes BE). This species differs from R. gilmorei in the presence of straight teeth and fully serrated mesial carinae. Richardoestesia asiatica cannot be distinguished from R. isosceles Sankey, 2001, which we consider a nomen dubium due, in part, to the imperfect nature of its holotype. Discriminant function analysis (DFA) of dental measurements found no distinction between the samples from Khodzhakul and Bissekty formations. In DFA including North American samples, the morphospace of R. asiatica completely overlaps that of the sample from the Lance Formation (Maastrichtian) of Wyoming and only partly overlaps with that of the sample from the Milk River Formation (Santonian) of Alberta.
Tyrannosaurid Teeth from the Lomas Coloradas Formation Sonora Mexico
This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/authorsrights a b s t r a c t The Lomas Coloradas Formation (Cabullona Group, Upper Cretaceous) in the state of Sonora, Mexico, has yielded a great diversity of continental vertebrates, especially dinosaurs. In this study we describe, analyze and illustrate six theropod teeth (ERNO specimens) that were found isolated and surface collected. Identification of the specimens is based upon the methodology provided by Smith (2005), Smith et al. (2007) and Smith et al. (2005). The results showed that the ERNO teeth are comparable to those of tyrannosaurid dinosaurs and some of them probably correspond to a new taxon. Their referral to the Tyrannosauridae family is supported by the presence of semi-conical, laterally compressed crowns with an ovoid cross-sectional base; slightly offset carinae with chisel-shaped denticles that are wider labio-lingually than longer proximo-distally; and the presence of enamel wrinkles at the base of some denticles on the labial surface. These wrinkles are not prominent adjacent to the serrations but they take the form of high relief deep enamel bands across the labial and lingual crown faces. Statistical principal component analysis (PCA) and discriminant function analysis (DFA) corroborated the taxonomically assignation of these teeth into this family. Particularly, the DFA analysis yielded very interesting results. This analysis classified ERNO 8549, 8550, 8551 and 8552 specimens as belonging to Tyrannosaurus, so they represent the most southern record of this genus in Western North America. Finally, the misclas-sification of ERNO 005 and ERNO 006 specimens remains puzzling. It probably was the result of the presence of juvenile individuals.
Acta Palaeontologica Polonica, 2011
The Unenlagiinae is a clade of Gondwanan dromaeosaurid theropods mainly known from incomplete skeletal material. The group includes two recently discovered theropods, Buitreraptor and Austroraptor, from which cranial remains are available with in situ maxillary and dentary teeth, thus allowing the study of tooth morphology. Among the derived traits that diagnose the dentition of unenlagiines are: (i) high tooth count, (ii) small size of individual teeth when compared with skull height, (iii) absence of denticles and carinae, and (iv) presence of longitudinal grooves on the tooth crown. This suite of dental characteristics, shared between Buitreraptor and Austroraptor, can be considered as diagnostic of the Unenlagiinae or, at least, a more exclusive clade within the group. The teeth of Buitreraptor exhibit a remarkable labiolingual compression, whereas Austroraptor possesses more conical teeth, probably respective autapomorphic fea− tures. On one hand, these dental morphologies differ from those observed in most Laurasian dromaeosaurids and, for in− stance, could be considered as further proof of the purported vicariant evolution of the lineage on the southern continents. On the other hand, the morphological similarities (e.g., absence of denticles) between the teeth of unenlagiines and other theropod lineages, including Mesozoic birds and ornithomimosaurs, can be considered as the result of parallel trends re− lated to dental reduction.
Journal of Vertebrate Paleontology, 2019
Richardoestesia is an enigmatic theropod dinosaur originally described on the basis of a pair of dentaries (holotype of R. gilmorei Currie et al., 1990) and isolated distinctive teeth, which are abundant in the Upper Cretaceous of North America. Richardoestesia asiatica (Nesov, 1995) is represented by numerous isolated teeth from the Upper Cretaceous Khodzhakul, Bissekty, and Aitym formations of Uzbekistan. Richardoestesia asiatica shows the typical features of the genus, including small mesial and distal denticles (on average 28.4 and 34.5 denticles per 5 mm, respectively), rectangular or knob-like denticles, and an apically convex distal margin of the tooth crown. The sample of R. asiatica has a large proportion of straight teeth (morphotype A) and includes several types of recurved teeth related to their position in the jaws (morphotypes BE). This species differs from R. gilmorei in the presence of straight teeth and fully serrated mesial carinae. Richardoestesia asiatica cannot be distinguished from R. isosceles Sankey, 2001, which we consider a nomen dubium due, in part, to the imperfect nature of its holotype. Discriminant function analysis (DFA) of dental measurements found no distinction between the samples from Khodzhakul and Bissekty formations. In DFA including North American samples, the morphospace of R. asiatica completely overlaps that of the sample from the Lance Formation (Maastrichtian) of Wyoming and only partly overlaps with that of the sample from the Milk River Formation (Santonian) of Alberta.
A Functional Explanation for Denticulation in Theropod Dinosaur Teeth
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 dinosaur teeth from the lowermost Cretaceous Rabekke Formation on Bornholm, Denmark
Geobios, 2008
The dinosaur fauna of the palynologically dated lower Berriasian Skyttegård Member of the Rabekke Formation on the Baltic island of Bornholm, Denmark, is represented by isolated tooth crowns. The assemblage is restricted to small maniraptoran theropods, assigned to the Dromaeosauridae incertae sedis and Maniraptora incertae sedis. The dromaeosaurid teeth are characterized by their labiolingually compressed and distally curved crowns that are each equipped with a lingually flexed mesial carina and a distinctly denticulated distal cutting edge. A morphologically aberrant tooth crown (referred to as Maniraptora incertae sedis) has triangular denticles of uneven width, a feature occasionally found in Upper Cretaceous hesperornithiform toothed diving birds, but also in premaxillary teeth of the velociraptorine Nuthetes from the Lower Cretaceous of England.