Download or read book Cranial Morphology Taxonomy and Systematics of Pachycephalosaurids Dinosauria Ornithischia written by Aaron David Dyer and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pachycephalosauridae (pachcycephalosaurids) were small to medium sized bipedal ornithischians, known solely from the Late Cretaceous of North America and Asia. These dinosaurs are characterised by thick, often domed frontals and parietals (frontoparietal dome), which are thought to have been used in intraspecific head-butting combat rituals. The dome, along with their thickened skull bones have a high preservation potential, particularly compared to the rest of the skeleton. Thus, the vast majority of pachycephalosaurid fossils consist of their unique skull bones, and so much research on the group has focused on these elements. The morphology of the thickened skull roof is included in the diagnosis of every species, yet the skull roof changes dramatically through ontogeny, and numerous putative species have been reidentified as juvenile or subadult representatives of other species. In this thesis, I focus on exploring morphological variation amongst pachycephalosaurid skulls, particularly the frontoparietal dome, and address its utility in pachycephalosaurid taxonomy and phylogenetics. I begin with describing the anatomy of the only known specimen of the controversial Gravitholus albertae, from the Late Cretaceous of Alberta, Canada. The specimen represents a heavily fused partial skull roof, and the degree of fusion has prevented a detailed description of the specimen, thus the validity of the species has been repeatedly justified and challenged. Alternative taxonomic hypotheses suggest Gravitholus albertae may be synonymous with Hanssuesia sternbergi or Stegoceras validum). I utilise synchrotron μCT imaging to identify the locations of the holotype's fused contacts, which facilitates a detailed description of the specimen. Gravitholus albertae was then included with Hanssuesia sternbergi and Stegoceras validum in morphometric analyses, to evaluate the distinctness of these three species. There are no ontogenetic-independent features of "Gravitholus albertae" that would justify a unique species. Instead, Gravitholus albertae and Hanssuesia sternbergi are morphologically consistent with mature Stegoceras validum. Thus, Gravitholus albertae and Hanssuesia sternbergi are synonymous with Stegoceras validum. Interestingly, Stegoceras validum appears to possess adult dimorphism in the thickness of the frontonasal boss, which is not explained by previous taxonomic hypotheses. Instances of post-traumatic injuries, consistent with head-butting, appear restricted to individuals with thicker frontonasal bosses. The dimorphism in Stegoceras validum is interpreted as sexual dimorphism, with the thicker bossed sex engaging in ritualistic intraspecific combat. I then move onto assessing morphological variation in pachycephalosaurid frontoparietals by statistically testing previously proposed discrete character states used in phylogenetic analyses, attempt to identify new characters and states, and comment on the validity of Stegoceras novomexicanum. The use of several features previously used as structures for phylogenetic characters are supported, and the distinction of their character stares are statistically demonstrated. These states are broadly consistent with previous taxonomic assessments, although a few species in each revised character are reassessed. There is no morphological support for "Stegoceras novomexicanum" and is regarded as Pachycephalosauridae indeteterminate. "Stegoceras novomexicanum ", along with other invalidated pachycephalosaurids, were removed from a phylogenetic analysis based on a revised morphological character matrix. This phylogenetic tree of Pachycephalosauria (pachycephalosaurians) is broadly similar to pervious analyses. The main differences include recovering Colepiocephale lambei as a basal Pachycephalosaurinae (pachycephalosaurines), and a polyphyletic Sphaerotholus. Derived pachycephalosaurines appear to be united by a cranial dome that initially develops on the parietals (as opposed to initially developing on the frontals). This distinction deserves further investigation with histological and CT methodologies to determine the developmental pathways that different pachycephalosaurid species took to grow their domes.
Download or read book Dinosaur Systematics written by Kenneth Carpenter and published by Cambridge University Press. This book was released on 1992-07-31 with total page 360 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years dinosaurs have captured the attention of the public at an unprecedented scale. At the heart of this resurgence in popular interest is an increased level of research activity, much of which is innovative in the field of palaeontology. For instance, whereas earlier palaeontological studies emphasized basic morphologic description and taxonomic classification, modern studies attempt to examine the role and nature of dinosaurs as living animals. More than ever before, we understand how these extinct species functioned, behaved, interacted with each other and the environment, and evolved. Nevertheless, these studies rely on certain basic building blocks of knowledge, including facts about dinosaur anatomy and taxonomic relationships. One of the purposes of this volume is to unravel some of the problems surrounding dinosaur systematics and to increase our understanding of dinosaurs as a biological species. Dinosaur Systematics presents a current overview of dinosaur systematics using various examples to explore what is a species in a dinosaur, what separates genders in dinosaurs, what morphological changes occur with maturation of a species, and what morphological variations occur within a species.
Download or read book Cranial Morphology of Prosaurolophus Ornithischia Hadrosauridae written by John R. Horner and published by . This book was released on 1992 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Taxonomy Morphology Masticatory Function and Phylogeny of Heterodontosaurid Dinosaurs written by Paul C. Sereno and published by PenSoft Publishers LTD. This book was released on 2012-10-03 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: This major study on heterodontosaurid dinosaurs is the first to review the taxonomy, morphology, functional anatomy, and phylogeny of this important early radiation of small-bodied herbivores. Heterodontosaurids persisted for approximately 100 My, from Late Triassic to Early Cretaceous time, during which they evolved some of the most sophisticated dentitions for processing plant materials. Some species required reevaluation to establish unequivocally their status as heterodontosaurids, such as Echinodon from rocks in southern England, one of the first and smallest dinosaurs ever described. Tianyulong from northern China is described in more detail in the study and is shown to have unusual skeletal proportions, including a relatively large skull and very short forelimb. A new taxon, Pegomastax africanus gen. n. sp. n., is described from southern Africa with a short parrot-shaped bill. Tooth replacement and tooth-to-tooth wear is more common than previously thought among heterodontosaurids, which the author argues are herbivores despite their prominent caniniform teeth. Heterodontosaurds appear to have split early in their history into a northern group with primitive, subtriangular crowns and a southern group with deeper crown proportions.
Download or read book Phylonyms written by Kevin de Queiroz and published by CRC Press. This book was released on 2020-04-30 with total page 1353 pages. Available in PDF, EPUB and Kindle. Book excerpt: Phylonyms is an implementation of PhyloCode, which is a set of principles, rules, and recommendations governing phylogenetic nomenclature. Nearly 300 clades - lineages of organisms - are defined by reference to hypotheses of phylogenetic history rather than by taxonomic ranks and types. This volume will document the Real World uses of PhyloCode and will govern and apply to the names of clades, while species names will still be governed by traditional codes. Key Features Provides clear regulations for implementing new guidelines for naming lineages of organisms incorporates expressly evolutionary and phylogenetic principles Works with existing codes of nomenclature Eliminates the reliance on rank-based classification in favor of phylogenetic relationships Related Titles: Rieppel, O. Phylogenetic Systematics: Haeckel to Hennig (ISBN 978-1-4987-5488-0) Cantino, P. D. and de Queiroz, K. International Code of Phylogenetic Nomenclature (PhyloCode) (ISBN 978-1-138-33282-9).
Download or read book Anatomy and Classification of the North American Pachycephalosauria Dinosauria written by Hans-Dieter Sues and published by . This book was released on 1987 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ontogenetic and Stratigraphic Cranial Variation in the Ceratopsid Dinosaur Triceratops from the Hell Creek Formation Montana written by John Benedetto Scannella and published by . This book was released on 2015 with total page 530 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hypotheses regarding the taxonomy and systematics of non-avian dinosaurs are based on analyses of morphology. As such, it is critical to assess the potential roles of intraspecific variation in systematic interpretations. Ontogenetic (developmental) change has been found to be a potential contributor to taxonomic confusion in the fossil record of dinosaurs. Similarly, variation between specimens found at different stratigraphic levels should be assessed in order to decipher variation within and between closely related taxa. The chasmosaurine ceratopsid Triceratops has had a complicated taxonomic history due to variation in cranial morphology between specimens. Recent work in the uppermost Cretaceous Hell Creek Formation (HCF) has produced a large (n>50) new sample of specimens. Using this data set its possible to reassess variation in Triceratops and further explore chasmosaurine paleobiology. Building on previous work on Triceratops ontogeny, examination of the parietal-squamosal frill finds that these bones underwent a dramatic transformation late in ontogeny. The short, solid frill of Triceratops expanded into a more elongate, thin, fenestrated condition, which had previously been found to characterize the coeval ceratopsid taxon Torosaurus latus. This suggests that these taxa are synonymous with Torosaurus representing the mature form of Triceratops rather than a distinct taxon. Further, Nedoceratops hatcheri, which is represented by a single specimen with a small fenestra in the parietal, is hypothesized to represent a transitional morphology between unfenestrated and fully fenestrated (Torosaurus) specimens. Detailed locality information for specimens collected over the course of the Hell Creek Project permits for the placement of specimens in stratigraphic context. The two currently recognized species, T. horridus and T. prorsus, are stratigraphically separated within the HCF and cladistic and stratocladistic analyses are consistent with the evolution of Triceratops incorporating anagenetic (transformational) change. Morphometric analyses of the extant archosaur Ceratogymna atrata (the Black-casqued hornbill) indicate that enlarged cranial structures function as objects of visual display. Morphometric studies of Triceratops further suggest that specimens found lower in the formation may have attained the Torosaurus frill morphology through ontogeny, whereas this basal condition became increasingly rare higher in the formation. Morphometric results are also consistent with early divergence between two distinct genera.
Download or read book A New Skull of Parasaurolophus Dinosauria Hadrosauridae from the Kirtland Formation of New Mexico and a Revision of the Genus written by Robert M. Sullivan and published by New Mexico Museum of Natural History and Science. This book was released on 1999 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Variation in Papillar Morphology of Hadrosaur dinosauria Ornithischia Teeth Possible Taxonomic Utility written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Journal of Vertebrate Paleontology written by and published by . This book was released on 2012 with total page 500 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fossil Record 3 written by Robert M. Sullivan and published by New Mexico Museum of Natural History and Science. This book was released on 2011 with total page 747 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Cranial Morphology of the Hadrosaurian Dinosaurs of North America written by John H. Ostrom and published by . This book was released on 1961 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Late Cretaceous Vertebrates from the Western Interior written by Spencer G. Lucas and published by New Mexico Museum of Natural History and Science. This book was released on 2006-01-01 with total page 427 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Cranial Morphology and Systematics of Triceratops with a Preliminary Analysis of Ceratospsian Phylogeny written by Catherine Ann Forster and published by . This book was released on 2004 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Cranial Morphology and Systematics of Triceratops written by Catherine Ann Forster and published by . This book was released on 1990 with total page 686 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Cranial Morphology of the Hadrosaurian Dinosaurs of North America Bulletin of the AMNH V 122 Article 2 written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Age of Dinosaurs in Russia and Mongolia written by Michael J. Benton and published by Cambridge University Press. This book was released on 2003-12-04 with total page 744 pages. Available in PDF, EPUB and Kindle. Book excerpt: Unique reference volume covering major vertebrate fossil finds in former Soviet Union never before described in English.
