Dissertation Research: The Origin and Spread of Grass-dominated Ecosystems during the Late Tertiary of North America and How it Relates to the Evolution of Hypsodonty in Ungulates

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Proposal: DEB-1-0104975PI: N. C. Arens & C. StrombergDissertation Research: The origin and spread of grass-dominated ecosystems during the late Tertiary of North America and how it relates to the evolution of hypsodonty in ungulates.During the Miocene (18-15 million years ago), animals such as horses, camels, and rhinos independently evolved traits interpreted as adaptations to grasslands. These traits included high-crowned cheek teeth for processing coarse food and long legs for running. If these traits are truely adaptations, one must show that the traits arose at the same time or soon after grasslands appeared. This problem is difficult because plant fossils are absent in most places in North America where fossil animals are preserved. In conjunction with other evidence, such as those derived from pollen or paleosols, the use of a new type of plant fossil - phytoliths - will allow this problem to be circumvented. Phytoliths are microscopic silica bodies produced within the tissue of plants that allow the determination of life form (e.g., grasses versus shrubs versus tree). The proposed research will provide answers to three general questions. First, does a detailed record of phytoliths exist in North America that can be used to reconstruct vegetation type associated with animal fossils? Second, when and where do grasslands first appear in the Great Plains and how do they spread? Third, does the change to grass-dominated ecosystems happen before, coincident with, or after the evolution of animal traits associated with life in grasslands?