Browsing by Author "Montanari, Shaena A."
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Item A new dromaeosaurid from the Late Cretaceous Khulsan locality of Mongolia (American Museum novitates, no. 3965)(American Museum of Natural History., 2021-01-13) Turner, Alan H. (Alan Hamilton); Montanari, Shaena A.; Norell, MarkA new dromaeosaurid dinosaur, Shri devi, from the Late Cretaceous deposit of the Barun Goyot Formation at Khulsan, Mongolia, is described here. The Barun Goyot Formation (herein referred to as the Barun Goyot) is stratigraphically intermediate between the overlying Nemegt Formation and the underlying Djadokhta Formation, where much of the dromaeosaurid diversity has been reported to date. Sediments of the Barun Goyot are typically considered Upper Campanian in age. Although dromaeosaurid remains have been noted to occur in the Barun Goyot for decades, descriptive and taxonomic work has never been completed for the material. The holotype specimen (IGM 100/980) consists of a partially articulated individual preserving the right hind limb; left tibiotarsus; pelvis; and adjacent cervical, dorsal, and caudal vertebrae. IGM 100/980 is referable to a clade with Velociraptor based on the presence of a distinct ambiens tubercle located proximally on the anterior face of the pubis, a well-developed anterior tuberosity proximally located on the ischium, and a rounded longitudinal ischial ridge. It is distinguishable from V. mongoliensis based on a weak fourth trochanter (shared with all other dromaeosaurids) and deep anterior pedicular fossae in the cervical vertebrae; epipophyses in the last four cervicals are not raised but are instead represented by rugose circular scars. A suite of axial and appendicular characters are diagnostic for the new species. New discoveries including Shri devi allow for an improved understanding of dromaeosaurid anatomy, as well as the temporal and regional variation of the dromaeosaurid fauna of Mongolia and Inner Mongolia (Nei Mongol Autonomous Region, China), during the Late Cretaceous.Item Paleobiology, paleoecology, and morphology of vertebrates : new approaches to old questions.(2014-02-11) Montanari, Shaena A.Physical, chemical, and osteo-histological signatures in fossils can be extremely informative about organismal life history and ecological characteristics, yet these signatures have not yet been exploited to their fullest potential. Tools such as microscopy and mass spectrometry have the potential to address issues and questions in vertebrate paleontology that have, until now, remained elusive. First, this dissertation begins with traditional methods of anatomy and systematics with the addition of improved sampling and visualization of a historic specimen, Macrerpeton huxleyi. The edopoid temnospondyl Macrerpeton huxleyi is redescribed on the basis of new peels of the holotype. Phylogenetic analysis recovers Macrerpeton as the sister taxon of Cochleosaurus within the edopoid clade Macrerpetidae (formerly Cochleosauridae). Histological signatures in fossil bone can be used to reconstruct information about extinct organisms, such as genome size. Nonetheless, intra-skeletal osteocyte lacunae size variation, which could cause error in genome size estimation, has remained unexplored. While there is variance in the sizes of these bone structures over the skeleton of modern tetrapods, this variation is not necessarily causing any issues with genome size estimate; instead, the actual methods of estimation create a wide range of potential values that these methods are not able to answer certain genetic questions at a fine scale.Examining the carbon and oxygen isotopes in tooth enamel represents a quantitative method for discerning the paleoenvironments and paleoecology of fossil fauna. The Chinchilla Local Fauna from southeastern Queensland is a diverse assemblage of terrestrial Pliocene vertebrates from the Chinchilla Sand Formation. Isotopic analysis results from Chinchilla show that there were distinct dietary niches within the large marsupial vertebrate community. This study suggests that southeastern Queensland hosted a mosaic of tropical forests, wetlands and grasslands during the Pliocene. A review of the uses of biogenic materials in eggshells for stable isotope analysis is also provided. Stable isotope analysis is also used to determine paleoenvironments and paleoecology of dinosaurs during the Late Cretaceous in Mongolia. This study, which is the first to utilize stable isotope geochemistry on Mesozoic fossil tooth enamel from central Asia, documents that the environment was arid, but more importantly that dinosaur remains, such as eggshells, can be used for this type of study. These objectives are united by a need to use quantitative measurements to more accurately reconstruct vertebrate traits throughout earth history.