ANALYSIS OF INTRASPECIFIC AND ONTOGENETIC VARIATION IN THE DENTITION OF COELOPHYSIS BAURI (LATE TRIASSIC), AND IMPLICATIONS FOR THE SYSTEMATICS OF ISOLATED THEROPOD TEETH PDF Download

Author: Lisa G. Buckley
Publisher: New Mexico Museum of Natural History and Science
ISBN:
Category : Coelophysis
Languages : en
Pages : 73

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Author: Holly N. Woodward
Publisher: Indiana University Press
ISBN: 0253066476
Category : Science
Languages : en
Pages : 693

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Modern crocodylians—crocodiles, alligators, caiman (Central and South America), and gharials (India)—have evolved over 250 million years from a fully terrestrial, bipedal ancestor. Along with birds, crocodylians are the only living members of Archosauria, the group including nonavian dinosaurs. Ruling Reptiles features contributions on a broad range of topics surrounding crocodylian evolution and biology including osteology, osteohistology, developmental biology, myology, odontology, functional morphology, allometry, body size estimation, taphonomy, parasitology, ecology, thermophysiology, and ichnology. It demonstrates how the wide variety of these studies can also provide crucial insights into dinosaurian biology and evolution. Featuring the latest findings and interpretations, Ruling Reptiles: Crocodylian Biology and Archosaur Paleobiology is an essential resource for zoologists, biologists, and paleontologists.

Author: Lisa Glynis Buckley
Publisher:
ISBN:
Category : Coelophysis
Languages : en
Pages : 218

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Author: Joshua B. Smith
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Gavin Bradley
Publisher:
ISBN:
Category : Albertosaurus
Languages : en
Pages : 208

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The sparseness of the fossil record and the subjectivity of interpreting behaviour from morphological and taphonomic evidence have impeded studies on the behaviour of juvenile theropod dinosaurs. Most evidence for social behaviour in juvenile dinosaurs comes from multi individual bone beds or parent dinosaurs preserved while brooding on eggs or young. There is therefore a desire for alternative methods of assessing social behaviour, leading to the two key questions of this thesis: 1) can inferences about social behaviour be made using isolated specimens?, and 2) does gregariousness change with ontogeny in Gorgosaurus? A multidisciplinary study using isolated specimens of Gorgosaurus libratus, including a newly described juvenile specimen from Dinosaur Provincial Park in southern Alberta, was carried out in the hopes of answering these two questions. A review of social behaviour in modern animals suggests that gregariousness is gradational and varies from taxon to taxon, even within closely related groups such as Felidae. Inferences of social behaviour for dinosaurs based solely on phylogenetic bracketing is therefore not recommended. However, numerous analyses can be performed on isolated specimens in order to infer social behaviours including parental care, group living, sexual display and combat. For example, palaeopathologies may indicate intraspecific combat. Ontogenetic changes, such as growth curves, allometry of horns and crests, and changes in stable isotopes because of dietary changes may also indicate changing behavioural as well as ecological roles during development. Femoral circumferences are useful in inferring body mass of theropods, and in bone bed aggregations this can aid in studies of growth rates, which can inform social behaviour. Taphonomic damage can reduce sample sizes and make such studies problematic. Statistical analyses, however, suggest that three femoral-diameter-based estimation models may be used to predict femoral circumference measurements in tyrannosaurids. Ontogenetic morphological changes in Gorgosaurus may also inform inferences about social behaviour. Positive allometric growth of the lacrimal horns may imply a display function, as seen in modern bovid and cervid mammals. Slow maximum growth rates of juvenile Gorgosaurus, compared to other tyrannosaurids, calculated using lines of arrested growth and body mass estimations, may indicate social aggregation during early ontogeny in order to survive alongside faster growing and larger predators, such as Daspletosaurus or, alternatively, reduced growth due to nutritional stresses on juveniles. Macrowear patterns in the teeth of UALVP 49500 and UALVP 10, an adult specimen, exhibit four major types of tooth wear: enamel spalling, longitudinal facets, tip wear, and barrel-shaped puncture marks. Adult teeth were typified by tip wear, and juvenile teeth were typified by longitudinal wear facets. This is hypothesised to reflect a change in feeding behaviour during ontogeny, from shearing and slicing of meat, with high levels of tooth occlusion in the young, to the "puncture and pull" method previously hypothesized for adults. A slicing feeding method for juveniles is further supported by thinner teeth with higher denticle densities, smaller bite forces, and a more circular orbit shape that is less resistant to the strain of high bite forces on the skull. This multidisciplinary analysis shows that substantial ontogenetic change occurred in Gorgosaurus, and demonstrates that social behaviour may be inferred from isolated specimens. As well, a description of a juvenile Gorgosaurus libratus, UALVP 49500, presents the first examination of post cranial material in such a specimen, and supports a genus-level distinction between Albertosaurus sarcophagus and Gorgosaurus libratus.

Author: Carina Klein
Publisher:
ISBN:
Category : Ammonoidea
Languages : en
Pages : 25

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This project assesses intraspecific variation through the ontogeny of the ammonite Scaphites whitfieldi Cobban, 1951, from the Upper Cretaceous of the U.S. Western Interior. Our sample consists of 103 dorsoventral cross sections from nine localities that represent two lithofacies (shale and siltstone). We measured four shell parameters (ww/dm, ww/wh, uw/dm, and WER) to describe the ontogenetic changes in shell morphology. We investigated the variation at three growth stages: immediately after hatching (dm = 1 mm), the neanoconch (dm = 4 mm), and the submature stage (defined as at or near the base of the mature hooklike body chamber). In general, the shell becomes more discoidal through ontogeny with a narrower umbilicus and a more compressed whorl section. The results of the univariate analysis indicate that the variation is statistically significantly higher in the neanoconch than in either the hatchling or submature stage. This pattern is also apparent in the multivariate analysis in which the disparity increases markedly from the hatchling to the neanoconch and then decreases again at the submature stage. These results are consistent with the hypothesis that the neanoconch represents a transition in the life history of the animal to a more demersal mode of life followed by a canalization of morphology toward maturity. However, because the neanic transition occurs over a range of sizes, it is possible that some individuals may have already undergone these changes at dm = 4 mm, whereas others may not have, thus inflating the degree of variation. To resolve this issue in the future, it is critical to examine each ontogenetic trajectory individually to pinpoint the exact size at which the morphological changes occur. We also compared the values of ww/dm, ww/wh, uw/dm, and WER of the three growth stages for the sample from siltstone versus the sample from shale. The comparison reveals that the specimens from siltstone occupy lower regions of the morphospace, implying that these specimens are generally more compressed than those from shale. This difference may be related to selection pressures for improved hydrodynamic efficiency in the higher energy environment represented by siltstone.

Author: J. Michael Parrish
Publisher: Indiana University Press
ISBN: 0253009472
Category : Science
Languages : en
Pages : 313

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Drawn from a 2005 international symposium, these essays explore current tyrannosaurid current research and discoveries regarding Tyrannosaurus rex. The opening of an exhibit focused on “Jane,” a beautifully preserved tyrannosaur collected by the Burpee Museum of Natural History, was the occasion for an international symposium on tyrannosaur paleobiology. This volume, drawn from the symposium, includes studies of the tyrannosaurids Chingkankousaurus fragilis and “Sir William” and the generic status of Nanotyrannus; theropod teeth, pedal proportions, brain size, and craniocervical function; soft tissue reconstruction, including that of “Jane”; paleopathology and tyrannosaurid claws; dating the “Jane” site; and tyrannosaur feeding and hunting strategies. Tyrannosaurid Paleobiology highlights the far ranging and vital state of current tyrannosaurid dinosaur research and discovery. “Despite being discovered over 100 years ago, Tyrannosaurus rex and its kin still inspire researchers to ask fundamental questions about what the best known dinosaur was like as a living, breathing animal. Tyrannosaurid Paleobiology present a series of wide-ranging and innovative studies that cover diverse topics such as how tyrannosaurs attacked and dismembered prey, the shapes and sizes of feet and brains, and what sorts of injuries individuals sustained and lived with. There are also examinations of the diversity of tyrannosaurs, determinations of exactly when different kinds lived and died, and what goes into making a museum exhibit featuring tyrannosaurs. This volume clearly shows that there is much more to the study of dinosaurs than just digging up and cataloguing old bones.” —Donald M. Henderson, Royal Tyrrell Museum of Palaeontology

Author: Christophe Hendrickx
Publisher:
ISBN: 9781775573265
Category : Abelisauridae
Languages : en
Pages : 74

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Author: Barry K. B. Berkovitz
Publisher: Academic Press
ISBN: 012802884X
Category : Science
Languages : en
Pages : 354

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The Teeth of Non-Mammalian Vertebrates is the first comprehensive publication devoted to the teeth and dentitions of living fishes, amphibians and reptiles. The book presents a comprehensive survey of the amazing variety of tooth forms among non-mammalian vertebrates, based on descriptions of approximately 400 species belonging to about 160 families. The text is lavishly illustrated with more than 600 high-quality color and monochrome photographs of specimens gathered from top museums and research workers from around the world, supplemented by radiographs and micro-CT images. This stimulating work discusses the functional morphology of feeding, the attachment of teeth, and the relationship of tooth form to function, with each chapter accompanied by a comprehensive, up-to-date reference list. Following the descriptions of the teeth and dentitions in each class, four chapters review current topics with considerable research activity: tooth development; tooth replacement; and the structure, formation and evolution of the dental hard tissues. This timely book, authored by internationally recognized teachers and researchers in the field, also reflects the resurgence of interest in the dentitions of non-mammalian vertebrates as experimental systems to help understand genetic changes in evolution of teeth and jaws. Features more than 600 images, including numerous high-quality photographs from internationally-recognized researchers and world class collections Offers guidance on tooth morphology for classification and evolution of vertebrates Provides detailed coverage of the dentition of all living groups of non-mammalian vertebrates

Author: Hideki Endo
Publisher: Springer Science & Business Media
ISBN: 4431769331
Category : Science
Languages : en
Pages : 150

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This book presents selected works of contemporary evolutionary morphologists and includes such topics as broad scale reconstructions of the brain and ear of dinosaurs, inference of locomotor habits from cancellous bone architecture in fossil primates, and a comparison of the independently evolved manipulating apparatuses in the lesser and giant pandas. Insight is provided into the application of modern noninvasive technologies, including digital imaging techniques and virtual 3D reconstruction, to the investigation of complex anatomical features and coherences. In combination with traditional methods, this allows for the formulation of improved hypotheses on coordinated function and evolution. The creation of virtual translucent specimens makes it possible to realize the age-old dream of the classical anatomists: looking through the skin into the inner organization of an organism. On full display here is the dramatic and promising impact that modern imaging techniques have on scientific progress in evolutionary morphology.