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Description
The earliest Eocene marked the appearance of the first North American euprimates (adapids, omomyids). Despite the fact that leading hypotheses assert that traits involved in food acquisition underlie euprimate origination and early diversification, the precise role that dietary competition played in establishing euprimates as successful members of mammalian communities is unclear. This is because the degree of niche overlap between euprimates and all likely mammalian dietary competitors ("the euprimate competitive guild") is unknown. This research determined which of three major competition hypotheses - non-competition, strong competition, and weak competition - characterized the late Paleocene-early Eocene euprimate competitive guild. Each of these hypotheses is defined by a unique temporal pattern of niche overlap between euprimates and their non-euprimate competitors, allowing an evaluation of the nature of dietary competitive interactions surrounding the earliest euprimates in North America. Dietary niches were reconstructed for taxa within the fossil euprimate competitive guild using molar morphological measures determined to discriminate dietary regimes in two extant mammalian guilds. The degree of dietary niche separation among taxa was then evaluated across a series of fossil samples from the Bighorn Basin, Wyoming just prior to, during, and after euprimate origination. Statistical overlap between each pair of euprimate and non-euprimate dietary niches was determined using modified multivariate pairwise comparisons using distances in a multidimensional principal component "niche" space. Results indicate that euprimate origination and diversification in North America was generally characterized by the absence of dietary competition. This lack of competition with non-euprimates is consistent with an increase in the abundance and diversity of euprimates during the early Eocene, signifying that the "success" of euprimates may not be the result of direct biotic interactions between euprimates and other mammals. An examination of the euprimate dietary niche itself determined that adapids and omomyids occupied distinct niches and did not engage in dietary competition during the early Eocene. Furthermore, changes in euprimate dietary niche size over time parallel major climatic shifts. Reconstructing how both biotic and abiotic mechanisms affected Eocene euprimates has the potential to enhance our understanding of these influences on modern primate communities.
ContributorsStroik, Laura (Author) / Schwart, Gary T (Thesis advisor) / Reed, Kaye E (Committee member) / Campisano, Christopher J (Committee member) / Gunnell, Gregg F. (Committee member) / Arizona State University (Publisher)
Created2014
Description
The genus Steinius has been determined to be one of the earliest forms of omomyids after being hypothesized to belong in the earliest anaptomorphines dating back to the Eocene. This genus is thought to be one of the ancestors of later omomyids. Other ancestors would include an early omomyid with characteristics resembling the primitive characteristics of Steinius. There are two sister taxa belonging to this genus, Steinius annectens and Steinius vespertinus. Both taxa appear within the strata at Bighorn Basin in Wyoming, with S. annectens appearing in early forms of stratigraphy compared to S. vespertinus. Specimens of both taxa are also lacking with only jaw fragments and single teeth specimens being known today. Although much of Steinius is unknown, it can be associated with Tarsiiformes, or tarsiers. The specimens in this study consisted of lower jaw fragments that were assessed via a microscope containing a reticle calibrated for tooth measurements. These measurements and visual assessments could be used later in the study to determine the relatedness of both taxa. This thesis provides an assessment on the dental morphological characteristics of the genus Steinius that includes both qualitative and quantitative data. The relationship between both sister taxa of this genus is also discussed in detail with a comparison of the similarities found in both teeth. The results obtained from this evaluation showed that both taxa can be determined to be related. One key difference that was noted, however, is that S. annectens has an average tooth size that is larger than that of S. vespertinus and other early omomyids.
ContributorsLauchnor, Sarah Nicole (Author) / Penkrot, Tonya (Thesis director) / Zack, Shawn (Committee member) / School of Nutrition and Health Promotion (Contributor) / School of Human Evolution and Social Change (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05