28 results on '"ALBERTOSAURUS"'
Search Results
2. Breathing Life into Tyrannosaurus rex.
- Author
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Erikson, Gregory M.
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TYRANNOSAURUS rex , *TYRANNOSAURIDAE , *ALBERTOSAURUS , *DINOSAURS , *ANIMAL behavior , *BEHAVIOR - Abstract
Reports on evidence that suggests that Tyrannosaurus rex (T. rex) had a flexible appetite and was more sociable than was once thought. The debate over whether it was primarily a predator or a scavenger; Fossil finds that suggest gregarious behavior among the Tyrannosauridae; What the close relatives of the T. rex, albertosaurs, suggest about its behavior; Evidence about the eating habits of the T. rex.
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- 1999
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3. New tyrannosaur from the mid-Cretaceous of Uzbekistan clarifies evolution of giant body sizes and advanced senses in tyrant dinosaurs.
- Author
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Brusatte, Stephen L., Averianov, Alexander, Sues, Hans-Dieter, Muir, Amy, and Butler, Ian B.
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TYRANNOSAURUS , *ALBERTOSAURUS , *PHYLOGENY , *TOP predators , *TYRANNOSAURIDAE - Abstract
Tyrannosaurids--the familiar group of carnivorous dinosaurs including Tyrannosaurus and Albertosaurus--were the apex predators in continental ecosystems in Asia and North America during the latest Cretaceous (ca. 80-66 million years ago). Their colossal sizes and keen senses are considered key to their evolutionary and ecological success, but little is known about how these features developed as tyrannosaurids evolved from smaller basal tyrannosauroids that first appeared in the fossil record in the Middle Jurassic (ca. 170 million years ago). This is largely because of a frustrating 20+ million-year gap in the mid-Cretaceous fossil record, when tyrannosauroids transitioned from small-bodied hunters to gigantic apex predators but from which no diagnostic specimens are known. We describe the first distinct tyrannosauroid species from this gap, based on a highly derived braincase and a variety of other skeletal elements from the Turonian (ca. 90-92 million years ago) of Uzbekistan. This taxon is phylogenetically intermediate between the oldest basal tyrannosauroids and the latest Cretaceous forms. It had yet to develop the giant size and extensive cranial pneumaticity of T. rex and kin but does possess the highly derived brain and inner ear characteristic of the latest Cretaceous species. Tyrannosauroids apparently developed huge size rapidly during the latest Cretaceous, and their success in the top predator role may have been enabled by their brain and keen senses that first evolved at smaller body size. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
4. Albertosaurus (Dinosauria: Theropoda) material from an Edmontosaurus bonebed (Horseshoe Canyon Formation) near Edmonton: clarification of palaeogeographic distribution1.
- Author
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Bell, Phil R., Currie, Philip J., and Ryan, Michael
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ALBERTOSAURUS , *EDMONTOSAURUS , *PALEOGEOGRAPHY , *TYRANNOSAURIDAE , *THANATOCOENOSES , *MAXILLA ,HORSESHOE Canyon Formation (Alta.) - Abstract
Tyrannosaurid cranial bones - including a maxilla, dentary, and pterygoid - were collected from a monodominant Edmontosaurus bonebed in the Horseshoe Canyon Formation exposed near the city of Edmonton, Alberta, Canada. The maxilla can be identified as Albertosaurus sarcophagus based on the narrow interfenestral strut and relatively deep dental pits along the length of the palatal shelf. Cranial bones are interpreted to have come from a single large individual that was incorporated into the site during, or temporally close to, the formation of the final taphocoenosis. This discovery constitutes the northernmost record of A. sarcophagus, and helps to narrow the geographic gap of latest Cretaceous tyrannosaurs between Alberta and Alaska. The geographic distribution of A. sarcophagus - eclipsed only in areal extent by Tyrannosaurus rex in North America - attests to the adaptability of this species, which endured regional changes in climate that forced extirpation of many ornithischian taxa during deposition of the Horseshoe Canyon Formation. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
5. Enhancing bonebed mapping with GIS technology using the Danek Bonebed (Upper Cretaceous Horseshoe Canyon Formation, Edmonton, Alberta, Canada) as a case study1.
- Author
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Bramble, Katherine, Burns, Michael E., Currie, Philip J., and Farke, Andrew
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DIGITAL mapping , *GEOGRAPHIC information systems , *ALBERTOSAURUS , *EDMONTOSAURUS , *SQL ,HORSESHOE Canyon Formation (Alta.) - Abstract
The Danek Bonebed is a monodominant Edmontosaurus bonebed preserving predominantly disarticulated material from the Upper Campanian Horseshoe Canyon Formation within the city limits of Edmonton, Alberta, Canada. To date, at least six dinosaur taxa have been identified at the site: Albertosaurus sarcophagus, Chasmosaurinae indet., Dromaeosauridae indet., Edmontosaurus regalis, Ornithomimidae indet., and Troodontidae indet. This bonebed has been used as a case study for creating a digital, searchable bonebed map using a geographic information system (GIS) platform. The original quarry maps produced on site are refined when digitized with new anatomical information gathered during preparation of collected specimens. Each specimen is labeled with the known specimen identification, quarry coordinates, and catalogue number. Creating a digital map of the bonebed allows easier interpretation of data and the ability to share maps to compare specific elements within the bonebed. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
6. Multivariate analysis of isolated tyrannosaurid teeth from the Danek Bonebed, Horseshoe Canyon Formation, Alberta, Canada1.
- Author
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Torices, Angelica, Reichel, Miriam, Currie, Philip J., and Ryan, Michael
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MULTIVARIATE analysis , *FOSSIL teeth , *TYRANNOSAURIDAE , *EDMONTOSAURUS , *ALBERTOSAURUS , *TROODON ,HORSESHOE Canyon Formation (Alta.) - Abstract
A significant number of fossil remains of the hadrosaurid Edmontosaurus have been recovered from the Danek Bonebed (Horseshoe Canyon Formation, Upper Cretaceous, Alberta). Bones from theropod dinosaurs are scarce in this hadrosaur-dominated bonebed, but more than 60 tyrannosaurid theropod teeth have been found. The isolated tyrannosaurid teeth include juvenile and adult specimens, although the precise ontogenetic stage has not been determined. The use of multivariate analyses helps determine the variance of the sample and verifies the initial taxonomic affinities given to these teeth, showing their high potential as a useful tool to better discriminate tyrannosaurid teeth. It also provides an insight into the tyrannosaurid intraspecific variability in the Horseshoe Canyon Formation. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
7. The first appearance of Troodon in the Upper Cretaceous site of Danek Bonebed, and a reevaluation of troodontid quantitative tooth morphotypes1.
- Author
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Torices, Angelica, Funston, Gregory F., Kraichy, Shannon T., Currie, Philip J., and Farke, Andrew
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TROODON formosus , *FOSSIL teeth , *PACHYCEPHALOSAURIDAE , *DINOSAURS , *ALBERTOSAURUS , *EDMONTOSAURUS , *CRETACEOUS paleogeography - Abstract
The systematic position of the small theropod dinosaur Troodon has had a confusing history and has been identified at different times as a lizard, a pachycephalosaurid, and a coelurosaurid. Troodon is now most commonly considered as a sister taxon to Dromeaosauridae, within Maniraptora. This study records the first evidence of Troodon in the Danek bonebed, an organic-rich member of the upper Campanian Horseshoe Canyon Formation. A single tooth (UALVP 55489) was recovered during the 2012 dig season, and it is exceptionally well-preserved. Its discovery prompted a reevaluation of variation within troodontid teeth in Alberta; it is compared here with 110 troodontid teeth from the Dinosaur Park, Horseshoe Canyon, and Wapiti formations. The results show that no distinctive morphotypes can be separated, in contrast to the results of other studies. This suggests that either troodontid teeth are not sufficiently different for identifying different species or that only one troodontid taxon is present in the Campanian of Alberta. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
8. Palaeopathological changes in a population of Albertosaurus sarcophagus from the Upper Cretaceous Horseshoe Canyon Formation of Alberta, Canada.
- Author
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Bell, Phil R.
- Subjects
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ALBERTOSAURUS , *PALEOPATHOLOGY , *ANIMAL populations , *ARCHAEOLOGICAL excavations , *BONES , *FOSSIL animals ,HORSESHOE Canyon Formation (Alta.) - Abstract
Over the past decade, excavations of a monodominant theropod bonebed from the lower Maastrichtian beds of the Horseshoe Canyon Formation have recovered a minimum number of 26 individuals of the tyrannosaur, Albertosaurus sarcophagus. Examination of skeletal elements from the bonebed revealed a small number of abnormalities from at least two individuals. These include bony spurs (enthesophytes) of unknown origin on three pedal phalanges. Well-healed fracture calluses are present on two rib shafts and a gastralia element. The left dentary of one adult preserves both healed and unhealed parallel bite marks and a perforative lesion attributable to a partially healed, mechanically induced puncture wound. Unfortunately, the limited range in the types and frequencies of pathological changes provides only little information on the distribution of such phenomena but may be suggestive of the overall 'health' of the population. Au cours de la dernière décennie, des excavations d'un gisement d'ossements à théropodes monodominant dans des lits du Maastrichtien inférieur de la Formation de Horseshoe Canyon ont produit un minimum de 26 exemplaires du tyrannosaure Albertosaurus sarcophagus. L'examen d'éléments squelettiques provenant du gisement a révélé un petit nombre d'anomalies chez au moins deux exemplaires, dont des éperons osseux (enthésophytes) d'origine inconnue sur trois phalanges pédieuses. Des cals de fractures bien consolidées sont présents sur deux diaphyses de côte et un élément de gastralium. L'os dentaire gauche d'un adulte conserve des marques de morsure parallèles guéries et non guéries, ainsi qu'une lésion perforante attribuable à une plaie punctiforme d'origine mécanique partiellement guérie. Malheureusement, la gamme limitée des types et des fréquences de modifications pathologiques ne fournit que peu d'information sur la distribution de ces phénomènes, mais pourrait être un indicateur de la « santé » globale de la population. [ABSTRACT FROM AUTHOR]
- Published
- 2010
9. A history of Albertosaurus discoveries in Alberta, Canada.
- Author
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Tanke, Darren H. and Currie, Philip J.
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ALBERTOSAURUS , *ANIMAL classification , *TYRANNOSAURIDAE , *SKULL , *SKELETON - Abstract
After many years of taxonomic uncertainty, Albertosaurus was established as a new genus in 1905, the year Alberta became a province of Canada. Gorgosaurus is a closely related tyrannosaurid from the Judithian beds of southern Alberta that was subsequently synonymized with Albertosaurus. Although most researchers consider the genera as distinct, there has been considerable confusion over the temporal and geographic range of Albertosaurus. Albertosaurus sarcophagus is only known from 13 skulls and (or) skeletons of varying completeness, and one (possibly two) bonebeds, all from the Horseshoe Canyon Formation (Campanian-Maastrichtian) of Alberta. Many of the major Albertosaurus specimens are scientifically compromised due to poor collection techniques, incomplete locality and stratigraphic information, politics, vandalism, accidents, gunplay, and landowner issues. The background of each specimen is discussed to eliminate some of the sources of confusion and to document how much of each specimen is preserved. Après de nombreuses années d'incertitude taxonomique, le nouveau genre Albertosaurus était établi en 1905, année où l'Alberta devenait une province du Canada. Par la suite, Gorgosaurus, un tyrannosauridé étroitement apparenté provenant de lits judithiens du sud de l'Alberta, était synonymisé avec Albertosaurus. Bien que la plupart des chercheurs considèrent que ces genres sont distincts, une certaine confusion règne concernant la portée temporelle et géographique d'Albertosaurus. La connaissance d'Albertosaurus sarcophagus ne repose que sur treize crânes ou squelettes de divers degrés de complétude et sur un (possiblement deux) gisement d'ossements, tous de la Formation de Horseshoe Canyon (Campanien-Maastrichtien) de l'Alberta. L'intégrité, du point de vue scientifique, de bon nombre des principaux spécimens d'Albertosaurus est compromise en raison de mauvaises techniques de prélèvement, de renseignements géographiques et stratigraphiques incomplets, de questions de nature politique, de vandalisme, d'accidents, de tirs d'armes à feu et de problèmes avec des propriétaires fonciers. Le contexte de chacun des spécimens est examiné afin d'éliminer certaines sources de confusion et de documenter le degré de préservation de chaque spécimen. [ABSTRACT FROM AUTHOR]
- Published
- 2010
10. The heterodonty of Albertosaurus sarcophagus and Tyrannosaurus rex: biomechanical implications inferred through 3-D models.
- Author
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Reichel, Miriam
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ALBERTOSAURUS , *TYRANNOSAURUS rex , *ANATOMY , *BONES , *BIOMECHANICS , *FOSSIL animals , *TOMOGRAPHY - Abstract
The objective of this study is to analyze how different crown morphologies and different root lengths respond to stresses generated by the bite forces of Albertosaurus sarcophagus and Tyrannosaurus rex. Six well-preserved teeth of A. sarcophagus from the Albertosaurus bonebed in Dry Island Park (southern Alberta) were selected to study their biomechanics, and T. rex teeth were included for comparison. The three-dimensional (3-D) models were obtained through computerized tomography (CT) scanning and 3-D digitizing. Finite element analyses were performed in Strand7®. Bite forces for Albertosaurus and Tyrannosaurus were calculated based on cranial and jaw proportions. The results were viewed with the Tresca yield criterion. The ratios of shear stresses observed along the mesio-distal versus labio-lingual axes of all models allows the identification of similar stress distribution patterns in the upper and lower jaws of Albertosaurus and the upper jaws of Tyrannosaurus, with a higher amount of shear along the mesio-distal axis occurring in the mid-maxillary teeth. The dentary teeth of Tyrannosaurus, however, show a different stress distribution pattern, with a higher amount of shear occurring along the labio-lingual axis of the mid-dentary teeth. These differences in jaw mechanics suggest that the function of teeth in the lower jaw of Tyrannosaurus shifted a few positions to compensate different proportions in the dentary that cause the anterior dentary teeth to be aligned with the largest maxillary teeth in Tyrannosaurus. These results suggest that heterodonty in these groups is different and that tooth form and function are sensitive to jaw proportions. Cette étude a pour but d'analyser la réponse de différentes formes de couronne et de différentes longueurs de racine aux contraintes induites par les forces de morsure d'Albertosaurus sarcophagus et de Tyrannosaurus rex. Six dents d'A. sarcophagus bien préservées provenant du lit à ossements d'Albertosaurus dans le parc de Dry Island (sud de l'Alberta) ont été choisies pour en étudier la biomécanique; des dents de T. rex ont également été étudiées à des fins de comparaison. Des modèles tridimensionnels des dents ont été obtenus par tomographie assistée par ordinateur et par numérisation 3-D. Des analyses par éléments finis ont été effectuées avec le logiciel Strand7MD. Le calcul des forces de morsure d'Albertosaurus et de Tyrannosaurus est basé sur les proportions du crâne et des mâchoires. Les résultats sont présentés avec le critère de résistance de Tresca. Les rapports entre les contraintes de cisaillement observées le long des axes mésiodistal, d'une part, et labiolingual, d'autre part, de tous les modèles révèlent des motifs semblables de répartition des contraintes dans les mâchoires supérieures et inférieures d'Albertosaurus et dans les mâchoires supérieures de Tyrannosaurus, un cisaillement plus important étant observé le long de l'axe mésiodistal des dents médiomaxillaires. Les dents dentaires de Tyrannosaurus présentent toutefois un motif de répartition des contraintes différent, un cisaillement plus important étant observé le long de l'axe labiolingual des dents médiodentaires. Ces différences sur le plan de la mécanique des mâchoires laissent croire à un décalage de quelques positions de la fonction des dents de la mâchoire inférieure de Tyrannosaurus en raison des proportions différentes de l'os dentaire qui font que, chez Tyrannosaurus, les dents dentaires antérieures s'alignent avec les plus grandes dents maxillaires. Ces résultats portent à croire que l'hétérodontie de ces groupes diffère et que la forme et la fonction des dents dépendent des proportions des mâchoires. [ABSTRACT FROM AUTHOR]
- Published
- 2010
11. Stratigraphy, sedimentology, and taphonomy of the Albertosaurus bonebed (upper Horseshoe Canyon Formation; Maastrichtian), southern Alberta, Canada.
- Author
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Eberth, David A. and Currie, Philip J.
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ALBERTOSAURUS , *BONES , *FOSSIL animals , *STRATIGRAPHIC geology , *SEDIMENTOLOGY , *TAPHONOMY ,HORSESHOE Canyon Formation (Alta.) - Abstract
The Albertosaurus bonebed provides evidence for the mass-mortality of at least 12 Albertosaurus. Albertosaurus, other vertebrates, and trees are concentrated on upper point bar surfaces of a small meandering paleochannel. Throughout the field area, Albertosaurus, other vertebrates, and coalified plants are also preserved patchily in overbank mudstones at the same horizon. Although the bonebed is dominated by Albertosaurus, there are also sparse macrofossil remains of Hypacrosaurus and Albertonykus. The basal lag yields vertebrate microfossils containing at least 19 additional taxa. Freshwater invertebrates are preserved at and below the base of the paleochannel. Large elements are over represented at the site, whereas smaller elements are under represented, suggesting hydraulic sorting. The taphonomic signature of the site suggests that death, disarticulation, and burial took place within one year. We conclude that one or more storms of large intensity downed trees and temporarily drowned the paleolandscape, ultimately killing the tyrannosaurids directly or indirectly. Logs and carcasses were reworked on a point bar during the waning stages of the storm and over subsequent years. Scavenging and breakage of remains by large carnivores was probably inhibited by the mixed log and bone jam. Remains of smaller scavengers (small theropods and snails) are plentiful suggesting these forms were more successful at accessing remains. Juvenile Albertosaurus are under represented at the site suggesting the possibility of age segregation. Because the group of Albertosaurus may have been forced together by rising floodwaters, it is not possible to assess the degree to which the taxon was gregarious from these data alone. Le gisement d'ossements d'Albertosaurus témoigne de la mortalité massive d'au moins douze Albertosaurus. Albertosaurus, d'autres vertébrés et des arbres sont concentrés sur des surfaces supérieures de barre de méandre d'un petit paléochenal méandrique. Dans toute la région, Albertosaurus, d'autres vertébrés et des plantes carbonisées sont également préservés par endroits dans des mudstones de débordement situés au même horizon. Bien que le gisement d'ossements soit dominé par Albertosaurus, il présente également ça et là des restes de macrofossiles d'Hypacrosaurus et d'Albertonykus. Le dépôt de déflation à la base du paléochenal présente des microfossiles de vertébrés d'au moins 19 autres taxons. Des invertébrés d'eau douce sont préservés à la base du paléochenal et sous celle-ci. Les grands éléments sont sur-représentés dans le site, alors que les éléments plus petits sont sous-représentés, ce qui suggère un tri hydraulique. La signature taphonomique du site suggère que la mort, la désarticulation et l'enfouissement ont eu lieu dans la même année. Il est conclu qu'une ou plusieurs tempêtes de forte intensité ont abattu les arbres et provisoirement noyé le paléopaysage, entraînant finalement la mort directe ou indirecte des tyrannosauridés. Les billots et les carcasses ont été remaniés sur une barre de méandre vers la fin de la tempête et au cours des années subséquentes. L'embâcle de billes et d'ossements a probablement empêché la récupération et le bri des restes par des grands carnivores. La présence de nombreux restes de détritivores plus petits (petits théropodes et escargots) donne à penser que ces animaux pouvaient accéder aux restes plus efficacement. Les Albertosaurus juvéniles sont sous-représentés dans le site, ce qui porte à croire à une ségrégation selon l'âge. tant donné que la montée des eaux pourrait avoir provoqué le rassemblement du groupe d'Albertosaurus, il est n'est pas possible d'évaluer le degré de grégarisme de ce taxon à la lumière de ces seules données. [ABSTRACT FROM AUTHOR]
- Published
- 2010
12. A revised life table and survivorship curve for Albertosaurus sarcophagus based on the Dry Island mass death assemblage.
- Author
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Erickson, Gregory M., Currie, Philip J., Inouye, Brian D., and Winn, Alice A.
- Subjects
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ALBERTOSAURUS , *ARCHAEOLOGICAL finds , *BONES , *FOSSIL animals , *ZOOARCHAEOLOGY - Abstract
In 1910 a crew from the American Museum of Natural History discovered a bone bed composed primarily of the large tyrannosaurid Albertosaurus sarcophagus in what is now Dry Island Buffalo Jump Provincial Park in Alberta, Canada. Study of the remains from the site allowed the first life table and survivorship curve for a non-avian dinosaur to be created. These have served as a model for subsequent studies of dinosaurian population biology. Since 2006, the discovery and preparation of hundreds of new elements from the bone bed stand to substantially increase the minimum number of individuals (MNI) represented. This would allow testing of previous conclusions regarding the population biology of these animals and refinement of our understanding of the patterns of survivorship. Here, four formerly unrecognized individuals from the Dry Island assemblage are revealed and a revised life table presented. As in the previous analysis, a left skewed age distribution and sigmoidal survivorship pattern were found. Annual mortality rates averaged 3.47% between ages two and 13 and then increased to a mean of 19.5% prior to extinction of the cohort after 28 years of age. Mean life expectancy for individuals surviving to two years of age was 15.19 years. Mid-life increase in attrition corresponds to entrance into the breeding population. The MNI is unlikely to substantially increase, and new individuals are unlikely to affect the pattern of survivorship inferred here. Nevertheless, future excavations stand to reveal more about the anatomical and pathological variance within the Dry Island Albertosaurus population. En 1910, une équipe du American Museum of Natural History découvrait un gisement d'ossements composé principalement de restes du grand tyrannosauridé Albertosaurus sarcophagus, dans l'actuel territoire du parc provincial de Dry Island Buffalo Jump, en Alberta (Canada). L'étude des restes prélevés du site permettait l'établissement des premières table de vie et courbe de survie pour un dinosaure non aviaire, qui ont servi de modèles pour des études subséquentes de la biologie des populations des dinosaures. La découverte et la préparation, de puis 2006, de centaines de nouveaux éléments provenant du gisement d'ossements devraient accroître considérablement le nombre minimum d'exemplaires (NME) représentés, ce qui permettrait de vérifier des conclusions antérieures concernant la biologie des populations de ces animaux et d'améliorer la compréhension des patrons de survie. Quatre exemplaires provenant de Dry Island qui, à ce jour, n'étaient pas reconnus sont révélés ici, et une table de vie révisée est présentée. Comme dans l'analyse précédente, une distribution des âges désaxée vers la gauche et un patron de survie sigmoïde sont obtenus. La moyenne des taux de mortalité annuelle est de 4,47 % pour les exemplaires de deux à 13 ans, et augmente à 19,5 % pour les exemplaires de 28 ans et plus, avant l'extinction de la cohorte. L'espérance de vie moyenne pour les exemplaires qui atteignent deux ans est de 15,19 ans. L'augmentation de l'attrition à mi-vie correspond à l'entrée dans la population en âge de reproduction. Il est peu probable que le NME augmente de manière importante et que l'ajout de nouveaux exemplaires change le patron de survie obtenu. Ceci dit, de nouvelles excavations devraient fournir plus d'information sur la variance anatomique et pathologique au sein de la population d'Albertosaurus de Dry Island. [ABSTRACT FROM AUTHOR]
- Published
- 2010
13. A taxonomic assessment of the type series of Albertosaurus sarcophagus and the identity of Tyrannosauridae (Dinosauria, Coelurosauria) in the Albertosaurus bonebed from the Horseshoe Canyon Formation (Campanian-Maastrichtian, Late Cretaceous).
- Author
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Carr, Thomas D.
- Subjects
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ALBERTOSAURUS , *TYRANNOSAURIDAE , *BONES , *FOSSIL animals , *ANIMAL classification , *CRETACEOUS paleontology ,HORSESHOE Canyon Formation (Alta.) - Abstract
The type series of Albertosaurus sarcophagus, consisting of a type (CMN 5600) and a paratype (CMN 5601) is inadequately established, since it has not been demonstrated that the specimens represent the same taxon. This problem has arisen because the original diagnostic characters have a wider distribution among Tyrannosauridae or they are in error, and both specimens consist of incomplete and damaged skulls. The type series was studied to test for the presence of diagnostic characters in the type specimen and, if so, to provide a rationale for referring the paratype to the taxon. Of the bones shared between the skulls, only five could be compared. One character, the enlarged posterior pneumatic recess of the palatine, is shared between the two specimens; this condition differs from the situation seen in other tyrannosaurids. This character provided the rationale for assessing the identity of the specimens collected from the Albertosaurus bonebed, from which one palatine was collected that exhibits the diagnostic recess. Isolated cranial bones from the bonebed were compared with those preserved in the type series to evaluate their referral to A. sarcophagus; additional characters shared between the type series and the specimens from the bonebed were identified in the maxilla, lacrimal, and palatine. This evidence supports the hypothesis that A. sarcophagus is the tyrannosaurid preserved in the bonebed. A hypothesis of the principal growth changes in the skull in A. sarcophagus, which includes the type series and bonebed material, is proposed. La série type d'Albertosaurus sarcophagus, qui consiste en un type (CMN 5600) et un paratype (CMN 5601), n'est pas bien établie, puisqu'il n'a pas été démontré que ces spécimens représentent le même taxon. Ce problème est dûau fait que les caractères diagnostiques définis à l'origine ont une distribution élargie au sein des tyrannosauridés ou sont erronés, et que les deux spécimens représentent des crânes endommagés et incomplets. La série type a été étudiée afin de vérifier la présence des caractères diagnostiques dans le spécimen type et, le cas échéant, de justifier l'affectation du paratype au taxon. Des os présents dans les deux spécimens, cinq seulement ont pu être comparés. Un caractère, la grande cavité pneumatique postérieure du palatin, est commun aux deux spécimens; cette condition se distingue de la situation observée chez d'autres tyrannosauridés. Ce caractère a motivé l'évaluation de l'identité des spécimens prélevés du gisement d'ossements d'Albertosaurus, duquel un palatin a été recueilli qui présente la cavité diagnostique. Des os crâniens isolés prélevés du gisement d'ossements ont été comparés à ceux préservés dans la série type afin d'évaluer leur affectation à A. sarcophagus; d'autres caractères communs à la série type et aux spécimens provenant du gisement d'ossements ont été cernés dans l'os maxillaire, l'os lacrymal et le palatin. Ces observations appuient l'hypothèse voulant qu'A. sarcophagus soit le tyrannosauridé préservé dans le gisement d'ossements. Une hypothèse est proposée concernant les principales modifications, durant la croissance, du crâne d'A. sarcophagus, qui inclut la série type et le matériel provenant du gisement d'ossements. [ABSTRACT FROM AUTHOR]
- Published
- 2010
14. A new articulated freshwater fish (Clupeomorpha, Ellimmichthyiformes) from the Horseshoe Canyon Formation, Maastrichtian, of Alberta, Canada.
- Author
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Newbrey, Michael G., Murray, Alison M., Brinkman, Donald B., Wilson, Mark V. H., and Neuman, Andrew G.
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- *
FRESHWATER fishes , *ALBERTOSAURUS , *BONES , *FOSSIL animals , *CRETACEOUS paleontology ,HORSESHOE Canyon Formation (Alta.) - Abstract
Horseshoeichthys armaserratus, gen. et sp. nov., (Clupeomorpha: Ellimmichthyiformes: Sorbinichthyidae) is described from the Horseshoe Canyon Formation (Maastrichtian), Albertosaurus bonebed locality, Alberta, Canada. Horseshoeichthys armaserratus is classified as an ellimmichthyiform based on the following characters: the presence of a sixth infraorbital with a sensory canal that leads to the fifth infraorbital, absence of a supraorbital bone, subrectangular predorsal scutes, parietals in contact with each other at the midline, and two supramaxillae. The specimen is classified in the Sorbinichthyidae Family as it has abdominal ribs articulating in pits on the centra, posterior spines on predorsal scutes, and absence of a median spine on predorsal scutes. A new genus and species is proposed based on the presence of (anteriorly) Y-shaped mesethmoid, supraorbital, subrectangular predorsal scutes with coarse, rounded serrae on the posterior margin and a large anterior projection, scales with serrae on the circuli, and two postcleithra. This specimen represents the first freshwater ellimmichthyiform from the Upper Cretaceous of North America and the highest paleolatitude (59°N) occurrence known for the family. Furthermore, the dentary and centra have distinctive morphologies that are matched by specimens in microvertebrate localities from three underlying formations, including the Milk River Formation (Santonian), which indicates at least a 14 million year history for this lineage. Horseshoeichthys armaserratus, gen. et sp. nov., (Clupeomorpha: Ellimmichthyiformes: Sorbinichthyidae), de la localité du gisement d'ossements d'Albertosaurus de la Formation de Horseshoe Canyon (Maastrichtien), en Alberta, au Canada, est décrit. Horseshoeichthys armaserratus est affecté aux ellimmichthyiformes à la lumière des caractères suivants : la présence d'un sixième sous-orbitaire présentant un canal sensoriel qui mène au cinquième sous-orbitaire, l'absence d'un os sus-orbitaire, des plaques osseuses pré-dorsales sub-rectangulaires, des pariétaux en contact les uns avec les autres au niveau de la ligne médiane et deux sus-maxillaires. Le spécimen est affecté aux sorbinichthyidés puisqu'il présente des côtes abdominales s'articulant dans des fosses sur le centrum et des épines postérieures sur les plaques osseuses pré-dorsales, et que ces dernières n'ont pas d'épine médiane. Un nouveau genre et une nouvelle espèce sont proposés à la lumière de la présence d'un mésethmoïde (antérieurement) en forme de Y, d'un sus-orbitaire, de plaques osseuses pré-dorsales sub-rectangulaires présentant des stries arrondies et épaisses sur leur bord libre postérieur et une grande projection antérieure, d'écailles avec des stries sur le circulus et de deux postcleithra. Ce spécimen représente le premier ellimmichthyiforme d'eau douce du Crétacé supérieur de l'Amérique du Nord et l'exemple connu de cette famille provenant de la plus haute paléolatitude (59oN). En outre, le dentaire et le centrum présentent des morphologies particulières semblables à celles de spécimens trouvés dans des localités de microvertébrés de trois formations sous-jacentes, dont la Formation de Milk River (Santonien), ce qui indique une histoire d'au moins 14 millions d'années pour cette lignée. [ABSTRACT FROM AUTHOR]
- Published
- 2010
15. Upper Cretaceous palynostratigraphy of the Dry Island area.
- Author
-
Koppelhus, E. B. and Braman, D. R.
- Subjects
- *
CRETACEOUS stratigraphic geology , *BIOSTRATIGRAPHY , *ALBERTOSAURUS , *FOSSIL animals , *FOSSIL plants , *BONES ,HORSESHOE Canyon Formation (Alta.) - Abstract
The overall palynology of the upper Horseshoe Canyon Formation to lower Scollard Formation within the Edmonton Group is reviewed providing new insights into biostratigraphic relationships for the interval, including the recognition of unconformities in the stratigraphic package. The palynomorph recovery from the Horseshoe Canyon Formation and overlying units documents a number of significant events that allow the subdivision of the section. The Albertosaurus bonebed occurs within the lower Maastrichtian portion of the Edmonton Group. The bonebed is situated just below the base of the Scollardia trapaformis Palynomorph Zone, an important marker assemblage that has been documented from areas of the Yukon, Northwest Territories, Alberta, and Saskatchewan. This indicates that the bonebed lies at the top of the Mancicorpus vancampoi Zone. The transition between the zones is marked by a colour change in the sediments, the appearance of coals and organic-rich sediments above the transition, a decrease in numbers of vertebrate fossils, and the appearance of new pollen species. It is inferred that the observed changes reflect a climatic switch from dry to wetter conditions. At a large scale, palynomorph assemblages across this transition do not clearly indicate marked differences that can be attributed to the climatic change, with the exception of the appearance of Scollardia trapaformis and Mancicorpus gibbus in the assemblages. On a microscale of a few metres, there are changes in relative abundance of plant groups. Un examen de la palynologie globale de la partie supérieure de la Formation de Horseshoe Canyon à la partie inférieure de la Formation de Scollard, du Groupe d'Edmonton, jette un nouvel éclairage sur les relations biostratigraphiques dans cet intervalle, dont la reconnaissance de discordances stratigraphiques. Les palynomorphes trouvés dans la Formation de Horseshoe Canyon et les unités sus-jacentes documentent un certain nombre d'évènements importants qui permettent de subdiviser cet intervalle. Le lit à ossements d'Albertosaurus se trouve dans la partie maastrichtienne inférieure du Groupe d'Edmonton, juste en dessous de la zone de palynomorphe à Scollardia trapaformis, un important assemblage repère qui a été documenté dans diverses régions du Yukon, des Territoires du Nord-ouest, de l'Alberta et de la Saskatchewan. Cela indique que le lit à ossements se situe au sommet de la zone à Mancicorpus vancampoi. La transition d'une zone à l'autre est marquée par un changement de couleur des sédiments, l'apparition de charbons et de sédiments riches en matière organique au-dessus de la transition, la diminution du nombre de fossiles de vertébrés et l'apparition de nouvelles espèces de pollen. Les changements observés refléteraient le passage d'un climat sec à un climat plus humide. À grande échelle, les assemblages de palynomorphes qui caractérisent cette transition ne révèlent clairement aucune différence marquée pouvant être attribuée à des changements climatiques, à l'exception de l'apparition de Scollardia trapaformis et Mancicorpus gibbus au sein de l'assemblage. À l'échelle de quelques mètres, l'abondance relative de certains groupes de plantes varie. [ABSTRACT FROM AUTHOR]
- Published
- 2010
16. On gregarious behavior in Albertosaurus.
- Author
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Currie, Philip J. and Eberth, David A.
- Subjects
- *
ALBERTOSAURUS , *BONES , *CRETACEOUS paleontology , *ARCHAEOLOGICAL excavations , *FOSSIL animals , *BEHAVIOR ,HORSESHOE Canyon Formation (Alta.) - Abstract
One century ago, a field party from the American Museum of Natural History discovered a bonebed in the Upper Cretaceous Horseshoe Canyon Formation of Alberta, Canada. Excavations by that museum, the Royal Tyrrell Museum of Palaeontology, and the University of Alberta have revealed the presence of at least a dozen individuals - represented by articulated partial skeletons, associated skeletons, and disarticulated isolated elements - of Albertosaurus sarcophagus. Tyrannosaurids dominate the bonebed assemblage, which also includes an adult Hypacrosaurus altispinus, two individuals of Albertonykus borealis, and numerous other, predominantly terrestrial, vertebrates. Skeletal morphology, phylogenetic inference, monodominant bonebeds, trackway sites, and ecological inferences support the notion that some non-avian theropods were gregarious animals. And specifically in the Albertosaurus bonebed, associated geologic and taphonomic evidence do not rule out a behavioural component in this catastrophic, mass-death assemblage. Il y a de cela un siècle, une expédition de l'American Museum of Natural History découvrait un lit d'ossements dans la Formation de Horseshoe Canyon du Crétacé supérieur de l'Alberta (Canada). Des fouilles effectuées par du personnel de ce musée, du Royal Tyrrell Museum of Palaeontology et de l'Université de l'Alberta ont révélé la présence d'au moins douze individus d'Albertosaurus sarcophagus, représentés par des squelettes articulés partiels, des squelettes associés et des éléments désarticulés isolés. S'il est dominé par des tyrannosauridés, l'assemblage du lit d'ossements renferme également un spécimen adulte d'Hypacrosaurus altispinus, deux individus d'Albertonykus borealis, ainsi que de nombreux autres vertébrés principalement terrestres. La morphologie des squelettes, l'inférence phylogénétique, des lits d'ossements monodominants, des sites de pistes et des inférences écologiques appuient la thèse voulant que certains théropodes non aviaires aient été des animaux grégaires. En ce qui concerne plus particulièrement le lit d'ossements d'Albertosaurus, les données géologiques et taphonomiques associées appuient la thèse d'une composante comportementale pour expliquer la présence de cet assemblage témoignant d'une mortalité massive catastrophique. [ABSTRACT FROM AUTHOR]
- Published
- 2010
17. Quantifying tooth variation within a single population of Albertosaurus sarcophagus (Theropoda: Tyrannosauridae) and implications for identifying isolated teeth of tyrannosaurids.
- Author
-
Buckley, Lisa G., Larson, Derek W., Reichel, Miriam, and Samman, Tanya
- Subjects
- *
FOSSIL teeth , *ALBERTOSAURUS , *TYRANNOSAURIDAE , *DINOSAURS , *ONTOGENY , *MULTIVARIATE analysis , *PRINCIPAL components analysis , *ANIMAL populations - Abstract
Documenting variation in theropod dinosaurs is usually hindered by the lack of a large sample size and specimens representing several ontogenetic stages. Here, variation within 140 disassociated and seven in situ tyrannosaur teeth from the Upper Cretaceous (lower Maastrichtian) monodominant Albertosaurus sarcophagus (Theropoda: Tyrannosauridae) bonebed is documented. This sample represents the largest data set of teeth from one population of A. sarcophagus containing both adult and juvenile specimens. Tooth variation was assessed using multivariate analyses (principal component, discriminant, and canonical variate analyses). Heterodonty in the teeth of A. sarcophagus contributes to the large amount of variation in the data set. Premaxillary teeth are significantly different from maxillary and dentary teeth, but there is no quantifiable difference between a priori identified maxillary and dentary teeth. Juvenile and adult teeth of A. sarcophagus show apparent quantitative differences that are size dependent on closer investigation, suggesting a cautious approach when interpreting multivariate analyses to identify novel tooth morphologies. Multivariate analyses on teeth of A. sarcophagus and published tooth data from other North American tyrannosaurid species reveals species-level clusters with little separation. The degree of separation among tooth clusters may reveal a phylogenetic signal in tyrannosaurid teeth. L'absence d'un échantillon de grande taille et de spécimens représentatifs de plusieurs stades ontogénétiques limite habituellement la capacité de documenter les variations chez les dinosaures théropodes. Les variations observées chez 140 spécimens non associés et sept spécimens in situ de dents de tyrannosaures du gisement d'ossements monodominant à Albertosaurus sarcophagus (Theropoda : Tyrannosauridae) du Crétacé supérieur (Maastrichtien inférieur) sont documentées. Cet échantillon constitue le plus vaste ensemble de données sur les dents d'une population d'A. sarcophagus renfermant des spécimens tant adultes que juvéniles. Les variations dentaires ont été évaluées à l'aide de différentes méthodes d'analyse multivariable (analyses en composantes principales, analyse discriminante et analyse des variables canoniques). L'hétérodontie des dents d' A. sarcophagus contribue à la grande variabilité de l'ensemble de données. S'il existe une différence significative entre les dents prémaxillaires et les dents maxillaires et dentaires, aucune différence quantifiable n'existe entre les dents maxillaires et les dents dentaires identifiées au préalable. Les dents juvéniles et adultes d'A. sarcophagus présentent des différences quantitatives qui, à la lumière d'un examen plus détaillé, s'avèrent dépendre de la taille. Cela souligne la nécessité d'une approche prudente à l'interprétation d'analyses multivariables dans le but d'identifier de nouvelles morphologies de dents. Des analyses multivariables de dents d'A. sarcophagus et de données publiées sur des dents d'autres espèces de tyrannosauridés nord-américains révèlent des grappes de niveau spécifique présentant une très faible séparation. Le degré de séparation entre les différentes grappes de dents pourrait indiquer un signal phylogénétique enregistré par les dents de tyrannosauridés. [ABSTRACT FROM AUTHOR]
- Published
- 2010
18. Faunal assemblages from the upper Horseshoe Canyon Formation, an early Maastrichtian cool-climate assemblage from Alberta, with special reference to the Albertosaurus sarcophagus bonebed.
- Author
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Larson, Derek W., Brinkman, Donald B., and Bell, Phil R.
- Subjects
- *
ALBERTOSAURUS , *BONES , *FOSSIL animals , *ZOOARCHAEOLOGY , *COLD weather conditions , *ARCHAEOLOGICAL finds ,HORSESHOE Canyon Formation (Alta.) - Abstract
The faunal assemblage from the early Maastrichtian portion of the Horseshoe Canyon Formation is described on the basis of four new vertebrate microfossil localities and remains from the Albertosaurus bonebed. All of the localities sampled were deposited during a cool, dry climate at a palaeolatitude of ~58°N. Thus, these assemblages provide insight into a northern cool-climate assemblage in the early Maastrichtian of western North America. This fauna is characterized by the presence of taxa with more northern affinities, such as Holostean A, champsosaurs, Troodon, and toothed birds. Warm-climate taxa, such as crocodylians, large and diverse turtles, and albanerpetontids are notable in their absence. The Albertosaurus bonebed locality at the top of unit 4 of the Horseshoe Canyon Formation was deposited during the initial stages of a trend to a warmer and wetter climate that is represented in unit 5. The bonebed shares many taxa with the underlying vertebrate microfossil localities. However, a notable difference is the presence of Atrociraptor marshalli from the Albertosaurus bonebed but not the other localities in the upper Horseshoe Canyon Formation. The presence of Atrociraptor may be attributable to this change in climate rather than local ecological conditions. Also, the assemblages are different in the paucity of fish remains in the bonebed, and the relative rarity of shed hadrosaur teeth. The low abundance of aquatic taxa and rarity of shed teeth of hadrosaurs indicate that the locality is largely autochthonous, with little material being transported into the site. L'assemblage faunique de la portion du Maastrichtien précoce de la Formation de Horseshoe Canyon est décrit à la lumière de quatre nouvelles localités de microfossiles de vertébrés et de restes provenant du gisement d'ossements d'Albertosaurus. Toutes les localités échantillonnées témoignent d'un dépôt en climat sec et frais à une paléolatitude d'environ 58°N. Ainsi, ces assemblages offrent une fenêtre sur un assemblage de climat nordique frais du Maastrichtien précoce de l'ouest de l'Amérique du Nord. Cette faune est caractérisée par la présence de taxons présentant des affinités plus nordiques, tels que des holostéens A, des champsosaures, Troodon et des oiseaux à dents. L'absence de taxons de climat chaud, tels que des crocodiliens, diverses tortues dont de grandes espèces et des albanerpetontidés, est notable. Les sédiments de la localité du gisement d'ossements d'Albertosaurus au sommet de l'unité 4 de la Formation de Horseshoe Canyon ont été déposés durant les stades initiaux d'une transition vers le climat plus chaud et plus humide représenté dans l'unité 5. Le gisement d'ossements présente bon nombre des mêmes taxons que les localités à microfossiles de vertébrés sous-jacentes. Toutefois, le fait qu'Atrociraptor marshalli soit présent dans le gisement d'ossements d'Albertosaurus, mais absent des autres localités de la partie supérieure de la Formation de Horseshoe Canyon constitue une différence notable. La présence d'Atrociraptor pourrait être attribuable au changement climatique susmentionné plutôt qu'à des conditions écologiques locales. La paucité de restes de poissons dans le gisement d'ossements et la rareté relative des dents d'hadrosaure tombées distinguent également le gisement d'ossements. La faible abondance de taxons aquatiques et la rareté de dents d'hadrosaure tombées indiquent qu'il s'agit d'une localité principalement autochtone caractérisée par une faible proportion de matériel apporté sur les lieux. [ABSTRACT FROM AUTHOR]
- Published
- 2010
19. COMPARATIVE ASSESSMENT OF TYRANNOSAURID INTERRELATIONSHIPS.
- Author
-
Sereno, Paul C. and Brusatte, Stephen L.
- Subjects
- *
COMPARATIVE studies , *CLADISTIC analysis , *HYPOTHESIS , *TYRANNOSAURIDAE , *ALBERTOSAURUS - Abstract
We employ a new comparative method to four cladistic analyses of tyrannosaurid dinosaurs to identify root causes for differences between phylogenetic results. The comparative method is a three-step procedure that (1) adjusts competing hypotheses so they share equivalent taxonomic scope, (2) isolates the character data relevant to the common problem, and (3) divides relevant character data into shared and novel partitions. It is then possible to quantify the degree of similarity between character data using three indices (ancestor similarity index, character similarity index and character state similarity index). The most parsimonious cladograms generated by the four analyses of tyrannosaurids appear fairly congruent, with two subclades present in all four analyses (Albertosaurus and Gorgosaurus versus Daspletosaurus, Tarbosaurus and Tyrannosaurus). A comparative examination of the underlying character data, however, highlights striking differences in character selection and significant differences in character state scores. Character selection and differences in scoring are root causes for phylogenetic incongruence. Comparative analysis reveals the existence of many data-level differences that remain largely obscuredwhen comparison is limited to the most parsimonious cladograms. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
20. Tyrannosaur Life Tables: An Example of Nonavian Dinosaur Population Biology.
- Author
-
Erickson, Gregory M., Currie, Philip J., Inouye, Brian D., and Winn, Alice A.
- Subjects
- *
DINOSAURS , *FOSSIL reptiles , *POPULATION biology , *MORTALITY , *TYRANNOSAURUS , *ALBERTOSAURUS , *LIFE spans , *PREDATION , *BREEDING - Abstract
The size and age structures for four assemblages of North American tyrannosaurs—Albertosaurus, Tyrannosaurus, Gorgosaurus, and Daspletosaurus—reveal a pronounced, bootstrap-supported pattern of age-specific mortality characterized by relatively high juvenile survivorship and increased mortality at midlife and near the maximum life span. Such patterns are common today in wild populations of long-lived birds and mammals. Factors such as predation and entrance into the breeding population may have influenced tyrannosaur survivorship. This survivorship pattern can explain the rarity of juvenile specimens in museum collections. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
21. Diversity of late Maastrichtian Tyrannosauridae (Dinosauria: Theropoda) from western North America.
- Author
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Carr, Thomas D. and Williamson, Thomas E.
- Subjects
- *
TYRANNOSAURIDAE , *DINOSAURS , *FOSSIL teeth , *ONTOGENY , *ANIMAL classification - Abstract
The tooth taxonAublysodon miranduswas reinstated following the collection of nondenticulate tyrannosaurid premaxillary teeth from late Maastrichtian deposits in western North America. A small skull from the Hell Creek Formation of Montana (the‘Jordan theropod’, LACM 28471), that was associated with a nondenticulate premaxillary tooth, was referred toAublysodonand the diagnosis was revised to include cranial bones. However, the‘premaxillary’ tooth of the specimen is actually a maxillary tooth. The small size ofAublysodoncrowns, and evidence that some denticles develop late in growth in theropods, indicates that the nondenticulate condition represents immaturity. Therefore,Aublysodonis a nomen dubium. The Jordan theropod was recently designated as the type specimen ofStygivenator molnari. A tyrannosaurid from the Hell Creek Formation of Montana (LACM 23845) was first referred toAlbertosauruscf.A. lancensisand then later became the type specimen ofDinotyrannus megagracilis. On the basis of shared derived characters and a quantitative reconstruction of the growth series ofTyrannosaurus rex, the type specimens ofS. molnariandD. megagracilisare juvenile and subadult specimens ofT. rex, respectively. There is currently evidence for only one tyrannosaurid species in the late Maastrichtian of western North America: T. rex. © 2004 The Linnean Society of London,Zoological Journal of the Linnean Society, 2004,142, 479–523. [ABSTRACT FROM AUTHOR]
- Published
- 2004
- Full Text
- View/download PDF
22. Introduction to Albertosaurus Special Issue.
- Author
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Currie, Philip J. and Koppelhus, Eva B.
- Subjects
- *
ALBERTOSAURUS , *BADLANDS , *FOSSIL animals , *DINOSAURS , *BONES , *ARCHAEOLOGICAL excavations - Published
- 2010
23. Introduction au numéro spécial sur Albertosaurus.
- Author
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Currie, Philip J. and Koppelhus, Eva B.
- Subjects
- *
ALBERTOSAURUS , *FOSSIL animals , *BADLANDS , *BONES , *ARCHAEOLOGICAL excavations - Published
- 2010
24. ERRATA.
- Subjects
- *
PERIODICALS , *ALBERTOSAURUS - Abstract
Presents corrections to the December 2004 issue of "Scientific American." Picture of an Albertosaurus in the article "The Dinosaurs of Arctic Alaska"; Correction to the article "The Scientific American 50"; Correction to the article "The Case of the Pilfered Planet."
- Published
- 2005
25. Amateur fossil hunters dig up trouble in Montana.
- Author
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Potera, Carol
- Subjects
- *
ALBERTOSAURUS , *PALEONTOLOGY - Abstract
Reports on the discovery of Albertosaurus fossil by amateur fossil hunters in Choteau, Montana. Rarity and significance of the fossil; Damage to the bones dug up caused by the inexperience of amateur fossil hunters Bruce and Janine Parker; Peebles family-owned Egg Mountain as one of the most famous fossil-hunting grounds; Past discoveries on the Peebles' property.
- Published
- 1995
- Full Text
- View/download PDF
26. Dinosaur Pack Hunters.
- Author
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Sullivan, Rachel
- Subjects
- *
TYRANNOSAURIDAE , *DIVISION of labor , *PREDATOR hunting , *ALBERTOSAURUS - Abstract
Discusses research evidences which suggest that tyrannosaurs were pack hunters and that they practiced division of labor. Degree of skeletal disarticulation in the remains of tyrannosaur Albertosaurus sarcophagus; Features of the pack hunting and division of labor practiced by the tyrannosaurs.
- Published
- 2001
27. Vigorous Youth for Tyrannosaurs.
- Author
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Stokstad, Erik
- Subjects
- *
TYRANNOSAURUS , *ALBERTOSAURUS , *MORTALITY , *DINOSAURS , *FOSSIL reptiles - Abstract
The article focuses on a study related to juvenile tyrannosaurs, conducted by researcher Gregory Erickson of Florida State University in Tallahassee. According to the study, the best time to be a tyrannosaur is childhood. The proportion of a birth cohort that manages to escape dying each year is revealed by the findings from the study through survivorship curves. For modem animals, researchers have plotted many such curves. From a Canadian site about 200 km northeast of Calgary, the team looked at 22 individuals of a tyrannosaur called Albertosaurus sarcophagus. The study found that the average mortality rate dropped to 3.5%. As juvenile tyrannosaurs tended to escape death, they are rare in the fossil record. When researchers examined bones from three other tyrannosaurs, Tyrannosaurus, Gorgosaurus, and Daspletosaurus, they found the same pattern of survivorship.
- Published
- 2006
- Full Text
- View/download PDF
28. Happy bonehunter.
- Author
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Grady, Wayne
- Subjects
- *
TYRANNOSAURUS rex , *ALBERTOSAURUS , *PALEONTOLOGY , *MUSEUMS - Abstract
Focuses on the discovery of Phillip Currie, chief paleontologist at the Royal Tyrrell Museum of Palaeontology. Predominant theory about Tyrannosaurus rex, Albertosaurus sarcophagus and Sinraptor dongi; Suspicion of Currie based on the hunting behavior of the theropods; Locating of the forgotten bonehead in August 1997.
- Published
- 1998
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