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Functional Significance of the Mandible, Tooth Roots, and Tooth Crowns, and their Implications for Fossil Dietary Inference

DeMers, Anessa C
http://orcid.org/0009-0009-2671-8153
http://rave.ohiolink.edu/etdc/view?acc_num=osu1683302044919227

Abstract Details

2023, Doctor of Philosophy, Ohio State University, Evolution, Ecology and Organismal Biology.
The tooth crowns, tooth roots, and mandible of mammals form an integrated apparatus for the acquisition and breakdown of food. The mandible houses the teeth and anchors the muscles of mastication, with its proportions determining the mechanical advantage along the tooth row; the tooth roots anchor the teeth in their sockets and dissipate the stresses of biting and chewing to the bone; the tooth crowns perform direct mechanical breakdown of food items. All three serve vital and distinct functions for a mammal’s ecology, and, of particular interest to paleontologists, all three tend to fossilize well, making them useful sources of dietary information for extinct mammals. Here, I analyze the functional signal that can be detected in the morphology of all three features, and where possible I use this dietary signal to infer details about the ecology of a group of extinct mammals known as archaic ungulates. Archaic ungulates are a group of morphologically similar lineages mostly dating to the early Paleogene that were numerous and diverse but which have been difficult to place both phylogenetically and ecologically. Looking at mandible shape of modern mammals, I find that phylogenetic signal tends to overwhelm dietary signal, making dietary inference difficult, but the dietary signal that is present indicates that archaic ungulates diversified in diet early in the Paleocene into niches that likely included specialized herbivory and faunivory. For the tooth roots, I conducted a survey of root number diversity in modern Mammalia, and found several previously unrecognized patterns in root number. I preliminarily establish that root number is not directly linked to tooth dimensions, tooth cusp number, or body size. It is also largely unrelated to diet, meaning that this while this character is far more complex than previously realized, it has no clear utility for dietary inference. For the tooth crowns, I performed a meta-analysis of studies that use one of the most popular measures of dental topography, orientation patch count (OPC). I find that, while OPC scores can have a clear link to carnivory and herbivory in some clades, across terrestrial amniotes as a whole there is no evidence of a pattern. I then use OPC as well as two additional dental topographic metrics, Dirichlet normal energy and the relief index, to quantify tooth crown functional diversity in archaic ungulates and modern mammals. I find results that echo my results for the mandible, that archaic ungulate dietary ecologies diversified early in the Paleocene and then maintained that diversity through time. My results highlight the strength of using multiple approaches to investigate dietary inference in extinct taxa, and point to places where our understanding of functional morphology can still be broadened.
John Hunter (Advisor)
Debbie Guatelli-Steinberg (Committee Member)
Jill Leonard-Pingel (Committee Member)
Jonathan Calede (Committee Member)
343 p.
Evolution and Development; Morphology; Paleontology
Dietary inference; archaic ungulates; geometric morphometrics; tooth crown topography; tooth root morphology; meta-analysis; orientation patch count

Recommended Citations

Citations

  • DeMers, A. C. (2023). Functional Significance of the Mandible, Tooth Roots, and Tooth Crowns, and their Implications for Fossil Dietary Inference [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1683302044919227

    APA Style (7th edition)

  • DeMers, Anessa. Functional Significance of the Mandible, Tooth Roots, and Tooth Crowns, and their Implications for Fossil Dietary Inference. 2023. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1683302044919227.

    MLA Style (8th edition)

  • DeMers, Anessa. "Functional Significance of the Mandible, Tooth Roots, and Tooth Crowns, and their Implications for Fossil Dietary Inference." Doctoral dissertation, Ohio State University, 2023. http://rave.ohiolink.edu/etdc/view?acc_num=osu1683302044919227

    Chicago Manual of Style (17th edition)

osu1683302044919227
342
© 2023, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.