Applications of strontium concentrations and isotopes preserved in vertebrate enamel and enamel-like tissues to paleoecology studies of Silurian conodonts from Gotland, Sweden, and Cretaceous Dinosaurs and Plesiosaurs from Alberta, Canada
Committee MemberHenderson, Charles
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AbstractPaleoecology is faced with the challenge of determining the behaviour of extinct animals without direct observation. Geochemical approaches offer one of the most promising avenues to study paleoecology problems such as potential migratory patterns. While original biochemical signals are often obscured in fossilized tissues as a result of diagenesis, tooth enamel is an exception due to its very high mineral content and low porosity. Though there are many potential biological signals preserved in fossil enamel, this thesis focused on the trace element strontium. By analyzing strontium isotope ratios preserved in the enamel of terrestrial dinosaurs, possible migratory behaviours were examined in both hadrosaurs and ceratopsians found at Dinosaur Provincial Park in the Late Cretaceous Dinosaur Park Formation of Alberta, Canada. The movements of a hadrosaur individual were determined to extend beyond the Dinosaur Provincial Park area to a location just under 100 km to the east of the park. In contrast, a herd of ceratopsians preserved in a bonebed were shown to have travelled as far as 200 km from either the north or west. Strontium isotope ratios were also examined in the enamel of plesiosaurs and enamel-like tissues of conodonts to determine if either group inhabited freshwater habitats. Plesiosaur teeth collected from fluvial deposits of the Dinosaur Park Formation were found to largely preserve a terrestrial signal, suggesting some plesiosaurs may have primarily inhabited freshwater environments. Conodont elements from Silurian marginal marine deposits in Gotland, Sweden were also examined with a focus on potential differences through ontogeny. The results confirmed the conodont taxa Ozarkodina confluens lived exclusively in marine settings and did not spawn or spend time in coastal freshwater environments. Finally, Sr/Ca and Ba/Ca ratios were analyzed in an entire conodont community from the Silurian of Gotland, Sweden. Results revealed convincing evidence for trophic partitioning between co-occurring conodont taxa. Compositional variations were observed between the two main tissues found in conodont crowns, white matter and lamellar tissue. These tissues occur in different proportions in different taxa, and these proportions need to be kept in mind when interpreting their geochemical data.
CitationTerrill, D. (2021). Applications of strontium concentrations and isotopes preserved in vertebrate enamel and enamel-like tissues to paleoecology studies of Silurian conodonts from Gotland, Sweden, and Cretaceous Dinosaurs and Plesiosaurs from Alberta, Canada (Unpublished doctoral thesis). University of Calgary, Calgary, AB.
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