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This study was conducted in order to determine whether the lagomorphs of 111 Ranch- Aztlanolagus agilis, Hypolagus arizonensis, and Sylvilagus cunicularius- could be distinguished based on femora. This is because while there is a large quantity of disarticulated lagomorph postcranial fossils from 111 Ranch, the chief diagnostic traits of A. agilis and H. arizonensis are the enamel patterns on their third premolars, leaving a large swath of specimens unidentifiable by diagnostic traits alone. Specimens from the Arizona Museum of Natural History were measured and compared to specimens known to be from these genera. Additionally, morphological traits in mandibles were used to identify mandible specimens, which in turn were used to identify fossils with the same specimen label. Statistical tests such as t-tests and principal components analyses were used to examine the distributions of sizes and locate clusters of datapoints likely corresponding to each genus. Some of these could be linked to a genus based on one particular specimen, P15156, which had been identified as Hypolagus based on its mandible morphology and size. The majority of the Museum'a specimens were thus associated with one of the three species, save for those which were too damaged and intermediate in size to confidently categorize.
ContributorsTkacik, Stephanie Marie (Author) / Farmer, Jack (Thesis director) / Reed, Kaye (Committee member) / McCord, Robert (Committee member) / School of Earth and Space Exploration (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
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