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Vertebrate Assemblages Of The Skelley Limestone (Conemaugh Group : Carboniferous, Gzhelian) In Noble And Muskingum Counties, Ohio, Daniel Austin Cline
Vertebrate Assemblages Of The Skelley Limestone (Conemaugh Group : Carboniferous, Gzhelian) In Noble And Muskingum Counties, Ohio, Daniel Austin Cline
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Three outcrops of the Gzhelian-aged Skelley Limestone (Casselman Formation, Conemaugh Group) were explored for vertebrate macrofossils and vertebrate microremains. The purpose of this exploration was to construct a better ecological history of the marine communities in the Late Pennsylvanian of eastern Ohio. Bulk limestone samples were collected, washed with acid, sieved and the resulting residues produced 21 distinct taxa of near-shore marine vertebrates. Osteichthyans were represented by an unknown palaeonisciform, an unknown platysomid, and an unknown palaeoniscoid. Holocephalians were represented by symmoriforms, helodontiforms, cochliodontiforms, and petalodontiforms. Elasmobranch groups included ctenacanthiforms and euselachians which contained representatives of hybodontiforms, protacrodontiforms, and neoselachians. …
Marine Vertebrate Communities From The Cisuralian Epoch (Permian Period) Of Central North America, Ryan C. Shell
Marine Vertebrate Communities From The Cisuralian Epoch (Permian Period) Of Central North America, Ryan C. Shell
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Marine vertebrates from the Cisuralian Epoch early Permian Period) are rare in the global fossil record. In particular, species-rich faunas from individual localities are poorly represented, with single occurrence localities that do not fully capture faunal tends in marine vertebrate ecology across this interval. This dissertation helps to close this gap by reporting marine vertebrate fossils from five localities across central North America, containing four to 15 unequivocal vertebrate taxa, as well as a new single occurrence locality near the Carboniferous-Permian boundary. This survey includes representatives from the first three of the four Cisuralian faunal stages, and is the result …
The Hydrostatics And Hydrodynamics Of Prominent Heteromorph Ammonoid Morphotypes And The Functional Morphology Of Ammonitic Septa, David Joseph Peterman
The Hydrostatics And Hydrodynamics Of Prominent Heteromorph Ammonoid Morphotypes And The Functional Morphology Of Ammonitic Septa, David Joseph Peterman
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Ammonoid cephalopods have chambered shells that regulated buoyancy. The morphology of their shells strongly influenced the physical properties acting on these animals during life. Heteromorph ammonoids, which undergo changes in coiling throughout ontogeny, are the focus of this dissertation. The biomechanics of these cephalopods are investigated in a framework involving functional morphology, paleoecology, and possible modes of life. Constructional constraints were investigated for the marginally-corrugated septal walls within the chambered ammonoid shell. These constraints governed the positive relationship between septal complexity and terminal size. Furthermore, increased septal complexity facilitated liquid retention via surface tension. More complex septa would have increased …
Convergent Evolution In Tooth Morphology Of Filter Feeding Lamniform Sharks, Michaela Grace Mitchell
Convergent Evolution In Tooth Morphology Of Filter Feeding Lamniform Sharks, Michaela Grace Mitchell
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The basking shark (Cetorhinus maximus) and megamouth shark (Megachasma pelagios) are two species of filter feeding sharks, both belonging to the order Lamniformes. There are two conflicting hypotheses regarding the origins of filter feeding in Lamniform sharks; that there is a single origin of filter feeding within Lamniformes, or conversely, the filter feeding adaptations have been developed independently due to different ancestral conditions. Evidence obtained from several studies strongly supports the latter hypothesis. Because evidence suggests that C. maximus and M. pelagios have developed their filter feeding adaptations independently, we expect to see convergent evolution taking place within these two …
A Morphometric Analysis Of The Highly Variable Clypeasteroid, Periarchus Lyelli, Lauren Elizabeth Williamson
A Morphometric Analysis Of The Highly Variable Clypeasteroid, Periarchus Lyelli, Lauren Elizabeth Williamson
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The Late Eocene echinoid, Periarchus lyelli (Conrad, 1834), known for its wide geographic range, high abundance, and specific stratigraphic range, is an ideal example of a guide fossil. However, due to its highly variable test morphology, many have questioned if, in fact, this sand dollar is actually two or three distinct species that have been misclassified. A preliminary study on this subject has been performed on specimens from Mississippi, North Carolina and South Carolina (Williamson, 2006), showing significant separation in test shapes. Continuing previous research, this study analyzes the test shapes of P. lyelli over its entire North American geographic …