Dietary ecology and community paleoecology of early Tertiary mammals

2008 2008

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Abstract (summary)

An understanding of the relationships and lineage ranges among Early Tertiary mammals is established, but a quantitative characterization of community-level changes as been slower to develop. I focused on the dietary ecology of mammals as the major criterion to describe their communities. Dietary hypotheses were proposed using stereoscopic observation of enamel microwear. I applied this method to 23 species of living carnivorans in order to relate those diets to their microwear. I recognized diets in microwear state space that are different from those known for herbivores. This method reliably discriminates diets of larger species. Microwear of the slicing carnassial teeth has to be evaluated in the light of masticatory differences among species. Styles of "omnivory" can also be identified with microwear.

I next applied this microwear method to a group of almost 90 species of Paleogene mammals. Most were browsers or mixed feeders, but some show divergence toward grazing. Microwear indicators of durophagy was recovered in some groups. Most archaic groups described were omnivorous, but their microwear reflects different types of omnivory.

The Eocene-Oligocene transition (37-30 Mya) was a critical period in mammalian history characterized by climatic cooling and drying. The White River Group (WRG) in North America is a long-term record of this transition. I combined my dietary characterizations with body size to establish feeding guilds Eo-Oligocene faunas. I found that the early Eocene faunas were dominated by browsing guilds with only a few species apparently specializing on grass. By the Chadronian, both grazing and browsing guilds were established, but both were dominated by a large mixed feeder group, in keeping with the open woodland of the time. This basic structure was sustained through the Orellan and Whitneyan of the WRG in a surprisingly consistent form. However, a contemporaneous Chadronian fauna in southwestern Montana is known to contain very different proportions of herbivores; I found that this fauna was dominated by browsers. The surprising degree of stasis in the WRG though this substantial climate change interval is probably the result of the fauna's initial assembly from the survivors of pre-Chadronian extinctions.

Indexing (details)

0418: Paleontology
Identifier / keyword
Earth sciences; Carnivora; Community paleoecology; Dental microwear; Dietary reconstruction; Eocene-Oligocene transition; Fossil mammals
Dietary ecology and community paleoecology of early Tertiary mammals
Dewar, Eric Walter
Number of pages
Publication year
Degree date
School code
DAI-B 69/12, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
Coombs, Margery C.
Committee member
Dumont, Elizabeth R.; Godfrey, Laurie R.; Hagadorn, James W.; Semprebon, Gina M.
University of Massachusetts Amherst
Organismic & Evolutionary Biology
University location
United States -- Massachusetts
Source type
Dissertations & Theses
Document type
Dissertation/thesis number
ProQuest document ID
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
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