PALEOECOLOGY OF MEDIAL CRETACEOUS DINOSAURS FROM WESTERN NORTH AMERICA.
This dissertation is broken into four chapters. In chapter I, I cover background literature and set the framework for the following chapters by describing the relationship between dinosaur ecology and ontogeny. In chapters 2 through 4 I cover different aspects of dinosaur paleoecology from the middle Cretaceous of North America.
In chapter II, the hypothetical ecologies are explored for multiple theropods derived from the Upper Cretaceous Mussentuchit Member of the Cedar Mountain Formation of Utah. The samples for this study come from six microsites, ranging in depositional setting from distal floodplain to channel lags. In total 866 teeth were analyzed, of which 309 were found to represent four unique tooth morphotypes: a large theropod, a medium-sized dromaeosaurid, a small dromaeosaurid, and a tooth-morph similar to the genus Richardoestesia. The four morphotypes vary significantly in mean size, from 15.1 mm in the large theropod (5.2–34.7 mm) to 3.7 mm in Richardoestesia (2.1–7.6 mm). Further, tooth representation from two of the best-sampled microsites show differing patterns. The large theropod teeth are about twice as common in the floodplain environment (V695, 15.6% of 135 teeth) as compared to the splay/channel (V794, 7.7% of 104 teeth); while medium-sized dromaeosaurid teeth are more than three times as common in the floodplain (12.5 to 41.5%). Small dromaeosaurid teeth show little difference between the sites (30.8 to 38.45%), but Richardoestesia teeth increase more than three-fold in abundance from the floodplain to the splay/channel (12.8 to 41.3%). Preliminary sedimentological and taphonomic data suggest that sorting bias is not responsible for the observed faunal differences. Stable isotope analysis (δ13CVPDB-LSVEC; δ18OVSMOW-SLAP) of tooth carbonate from the theropod morphotypes, goniopholidids (crocodylians), and matrix from V695 and V794 were also analyzed. Statistical differences between the matrix and theropod teeth for both δ13C and δ18O in V695 and for δ18O in V794, indicate that the samples have not been completely homogenized by diagenesis. The theropods show only small differences in δ13C values between each other, with morph 4 being the most depleted and most similar to goniopholidids in V695, as compared to the other theropods. In the sample fromV794 morph 2, which is the relatively most-enriched morphotype in V695, is the most-depleted morphotype in V794. In V695, morphs 1, 3, and 4 all show modest enrichment in δ13C indicating a level of dietary of plasticity not observed between the two different environmental samples for morph 2. Taken as a whole, we hypothesize that these data indicate that the Mussentuchit theropods had different habitat preferences, and presumably different niches within the predator guild. Most notably, morph 2, the medium-sized dromaeosaurid shows little difference in diet between sites indicating a stricter reliance on a single food source, presumably one not found near the channel. Richardoestesia (morph 4) conversely shows a wide-ranging diet depending on…
Advisors/Committee Members: Cifelli, Richard (advisor), Engel, Michael (committee member), Siler, Cameron (committee member), Kelly, Jeffrey (committee member), Czaplewski, Nicholas (committee member).
to Zotero / EndNote / Reference
APA (6th Edition):
Frederickson, J. (2018). PALEOECOLOGY OF MEDIAL CRETACEOUS DINOSAURS FROM WESTERN NORTH AMERICA. (Doctoral Dissertation). University of Oklahoma. Retrieved from http://hdl.handle.net/11244/301329
Chicago Manual of Style (16th Edition):
Frederickson, Joseph. “PALEOECOLOGY OF MEDIAL CRETACEOUS DINOSAURS FROM WESTERN NORTH AMERICA.” 2018. Doctoral Dissertation, University of Oklahoma. Accessed December 18, 2018.
MLA Handbook (7th Edition):
Frederickson, Joseph. “PALEOECOLOGY OF MEDIAL CRETACEOUS DINOSAURS FROM WESTERN NORTH AMERICA.” 2018. Web. 18 Dec 2018.
Frederickson J. PALEOECOLOGY OF MEDIAL CRETACEOUS DINOSAURS FROM WESTERN NORTH AMERICA. [Internet] [Doctoral dissertation]. University of Oklahoma; 2018. [cited 2018 Dec 18].
Available from: http://hdl.handle.net/11244/301329.
Council of Science Editors:
Frederickson J. PALEOECOLOGY OF MEDIAL CRETACEOUS DINOSAURS FROM WESTERN NORTH AMERICA. [Doctoral Dissertation]. University of Oklahoma; 2018. Available from: http://hdl.handle.net/11244/301329