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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 …
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 …