Browsing by Subject "Reptiles"
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Item An articulated Phytosaur skeleton: preparation techniques from field to exhibit(Texas Tech University, 1998-12) McQuilkin, Kyle S.Not availableItem Conservation of vertebrate biodiversity in Texas: Setting priorities for reserve selection(2006-12) Law, Jeffrey J.; Willig, Michael R.; McIntyre, Nancy E.; Cox, Stephen B.Species extinction rates are increasing throughout the world. A way to combat the global loss of species is through the creation of well-placed wildlife reserves. The principle objective of this study was to determine which areas throughout Texas most efficiently and effectively preserve extant vertebrate biodiversity (amphibians, reptiles, and mammals) if protected in reserves. Secondarily, I quantified the effectiveness of using a particular vertebrate class as a surrogate for others. The Sites Simulated Annealing Algorithm was used to determine areas that effectively preserve biodiversity while minimizing cost. This was accomplished through the use of irreplaceability values. Irreplaceability is equal to the number of times each planning unit is selected in a final solution to the SSAA. The SSAA was run 200 times for each scenario to determine this value. Species distribution maps obtained from the Texas GAP project were the basis for biodiversity data, whereas economic value of land came from the National Agriculture Statistics Service. I identified the best sites to establish reserves with current protected areas forced into the solution and also ignoring current protection status. The areas of the highest conservation concern, based on irreplaceability, were the Edwards Plateau of Central Texas and the Trans Pecos Region of West Texas. Although the irreplaceability values of planning units for incorporation into the reserve systems are correlated for all possible pairs of vertebrate classes, the associations are quite weak.Item Late Triassic dicynodonts: their anatomy, relationships, and paleobiogeography(Texas Tech University, 2000-05) Edler, Amy LNot availableItem Paleontology and geology of an upper Pennsylvanian tetrapod locality from the Ada Formation: Seminole County, Oklahoma(Texas Tech University, 1999-12) Kissel, Richard AnthonyThe paleontology, taphonomy, stratigraphy, depositional setting, and paleozoogeographic significance of an Upper Pennsylvanian tetrapod-bearing fossil locality is presented. The site, OMNH Locality V1005, is located within the Virgilian Ada Formation in southcentral Oklahoma, north of the town of Ada. The fossiliferous outcrop represents a meandering stream deposit, with the majority of the exposure consisting of fine-grained overbank (floodplain) deposits. The fossil material is found within a single horizon that stretches 11 meters along the face of the outcrop. This horizon is located within a gray mudstone unit and is 22.4 meters above the contact between the Ada Formation and the imderlying Vamoosa Formation. The bone-bearing interval is further characterized by the presence of granule-sized carbonate rock clasts and carbonized plant material. Tetrapod fossils recovered fi-om the Ada locality include the remains of at least six taxa, with remains of the pelycosaurian-grade synapsid Ophiacodon cf O. mirus constituting the majority (90 percent) of the fossil material collected and identified. Other taxa include the diadectid Diasparactus zenos, the temnospondyl ?Eryops sp., and three unidentified taxa known only from jaw fragments. An absolute minimum of five Ophiacodon individuals were recovered from the site, including the remains of both mature and immature individuals. Moreover, the material recovered from the Ada locality suggests, for the first time, the presence of size-based sexual dimorphism within the genus Ophiacodon. Linear measurements of the larger dimorph are approximately 1.5 times as great as those of the small form. No gender assignment is suggested. Of the five remaining taxa, no evidence supports the presence of more than one individual of each taxon. Except for four articulated vertebral segments, all of the fossil material collected in situ was disarticulated. The presence of articulated vertebral sequences, while all other skeletal elements are isolated and disarticulated, suggests that the vertebral column represents the last stage of the disarticulation sequence of an Ophiacodon corpse. The vertebral segments are straight and relaxed, which indicates that the corpses decomposed in water. All of the in situ bones are complete except for the anterior margin of a scapulocoracoid and the puboischiadic plate of a pelvic girdle. The bone surfaces exhibit no indication of cracking or flaking and, thus, were not exposed to prolonged periods of weathering at the surface. All fractures are indicative of post-burial breakage. The hypothesis that the bones were buried relatively quickly after the individuals' deaths is also supported by the lack of tooth marks and other evidence of scavenging. The fossil material represents a transported assemblage and the orientation of the long bones indicates that flow direction was either northwest or southeast during the time of deposition. Furthermore, the dip of several bones relative to the stratification suggests rapid deposition under flood conditions. OMNH Locality VI005 significantly extends the paleozoogeographic range of the taxa recovered. Diasparactus zenos is no longer restricted to the Upper Pennsylvanian deposits of El Cobre Canyon, New Mexico, and, thus, can no longer be considered endemic to that region. The Ada locality records the first Late Pennsylvanian report of Eryops outside of Pennsylvania. It also presents the first occurrence oi Ophiacodon within the Upper Pennsylvanian units of Oklahoma. Furthermore, O. mirus has been positively identified fi-om only the Lower Permian of New Mexico. If the Ada Ophiacodon is indeed referrable to O. mirus, then OMNH Locality VI005 extends both the stratigraphic and geographic range of this species to include the Upper Pennsylvanian of central Oklahoma.Item Parasuchid reptiles from the Triassic Dockum Group of West Texas(Texas Tech University, 1984-08) Shelton, Sally YvonneParasuchids (=phytosaurs) are characteristic Late Triassic archosaurian reptiles, comprising a family (Parasuchidae) most notable for its striking resemblance to modern crocodilians in superficial skeletal morphology and presumptive ecological niche. Fossil remains of parasuchids have been found in abundance in North America, India, Europe, and North Africa. The profusion of parasuchid fossils, as well as the range of distinct variations within the family, has made these reptiles important in the relative dating and correlation of Late Triassic continental sediments. Of the six genera of parasuchids considered in this study to have been established, four occur in North American deposits; all four are represented in the known vertebrate fauna of the Triassic Dockum Group of Texas.Item Preparation, casting, and exhibition of Texas aetosaur, Desmatosuchus(Texas Tech University, 2000-05) Herzog, NikoAetosaurs (Family Stagonolepididae) are an extinct group of quadrupedal heavily armored, herbivorous, archosaurian reptiles recorded from Upper Triassic deposits. Their remains are found in many parts of the world including North America, South America, Europe, India, Africa, and Greenland (SmaU, 1985; Heckert and Lucas, 1999). Aetosaurs first appeared during the Camian at the beginning of the age of dinosaurs, but became extinct at the end of the Triassic (Norian). They ranged in SVZJQ from Im to 6m in length. Worldwide, there are ten known genera, with seven occurring in the Chinle Formation and Dockum Group of the southwestern United States (Long and Murry, 1995). The North American genera include Desmatosuchus, Typothorax, Paratypothorax, Calyptosuchus, Longosuchus, Stagonolepis, and Stegomus.Item A review of the impacts of invasive grasses on herpetofauna(2015-08) Wright, Ian Michael; Gilbert, Lawrence E.; Leibold, Mathew ASpecies invasions pose one of the greatest threats to the maintenance and stability of biodiversity in ecosystems across the globe (Vitousek 1990). Plant species in particular are uniquely predisposed to successfully invade and establish themselves in novel habitats. In the United States alone invasive plants are responsible for nearly 35 billion dollars in economic and environmental damage. Grasslands are among the most productive ecosystems in the US and their biodiversity is threatened by continual introduction of alien grass species. These invasive grasses have a variety of direct and indirect effects on native grassland communities and have the ability to alter fire regimes, displace native species, and simplify grassland food webs. Little is known about the impacts invasive grasses have to amphibians and reptiles but there is evidence to suggest that these and other small organisms suffer direct mortality, impoverished prey sources, and reduced reproductive opportunities as a consequence of grass invasions. Here I summarize the current literature surrounding invasive grass impacts on herpetofauna and suggest topics of further research.Item The phylogeny and biostratigraphic utility of parasuchids from the Dockum group of West Texas(Texas Tech University, 1998-05) Simpson, Eric ONot availableItem The Triassic thecodontian reptile Desmatosuchus: osteology and relationships(Texas Tech University, 1985-12) Small, Bryan JohnNot availableItem Two new archosaur reptiles from the late Triassic of Texas(Texas Tech University, 2002-08) Atanassov, Momchil NikolaevTwo new basal archosaurs, Pteromimus longicollis and Procoelosaurus brevicollis are described from the Tecovas Formation (late Camian) and the Cooper Canyon Formation (early Norian) of the Dockum Group of West Texas. Pteromimus is based on an incomplete skull and associated and isolated skull and vertebral elements. The skull is high, with narrow snout, large orbit and naris, pneumatized maxilla and premaxilla, large inflated frontal, short parietal, plate-like supraoccipital, and reduced post-temporal openings. The dentition is thecodont and consists of conical teeth with fluted apices. The premaxillary teeth are long and slightly recurved, and the maxillary teeth are short and more laterally compressed. The vertebrae of both Pteromimus and Procoelos aurus £ire with procoelous and hollow centra, with large cavities for the interspinal ligament, well-developed epipophyses, and long and low neural arches carrying long neural processes v«th spine tables. Pteromimus is distinguished by low neural processes with weakly developed spine tables and ornamentation, while Procoelosaurus is characterized by higher neural processes that expand into wide spine tables with distinctive sculpturing. The cervical vertebrae of Pteromimus are elongate, dorsoventrally compressed, and bear unusual rib articulations consisting of a large posterior depression and a small anterior process. Procoelosaurus is represented by an association of vertebrae, pelvis, hindlimb and skull elements, and by a large number of isolated vertebrae. The maxilla and dentary of Procoelosaurus bear numerous teeth with thecodont implantation and crowns that are recurved, laterally compressed, and serrated. Procoelosaurus has at least three sacral vertebrae, large plate-like ischium, and ilium with a low blade, reduced preacetabular process, and a long, tapering postacetabular process. The femur appears similar to those of pterosaurs with anteriorly bowed shaft, well developed condyles, and an intumed head. The ankle and foot of Procoelosaurus are similar to those of early pterosaurs with an advanced mesotarsal tarsus, hooked fifth metatarsal, and closely appressed metatarsals I-IV subequal in length and indicating a plantigrade pes. A phylogenetic analysis of Archosauromorpha indicates that the two new reptiles and pterosaurs are omithodiran archosaurs and form a monophyletic clade that is the sister-group to Scleromochlus + Dinosauromorpha. Pteromimus is the sistergroup of pterosaurs, and Procoelosaurus is the sister-group to the clade Pteromimus + Pterosauria.