Master's Theses

Date of Award

Fall 2006

Degree Name

Master of Science (MS)

Department

Geosciences

Advisor

Richard Zawerksi

Abstract

Hesperornis regalis and other hesperornithiforms have long been compared to extant grebes or loons in terms of their ecology, mode of locomotion, and hind limb morphology. However, no quantitative analysis has previously been published to assess the accuracy of this morphological comparison. Ratio, multivariate, and average Euclidean distance analyses of five modern species of fool-propelled diver, including one loon and two grebes, indicate that the Common Loon, Gavia immer, is significantly similar to Hesperornis regalis, H. gracilis, and Parahesperornis alexi in terms of hind limb bone-length ratios, pelvis shape, and position of the acetabulum on the pelvis. The Western Grebe (Aechmophoris occidentalis) and the Red-necked Grebe (Podiceps grisegena) both appear to have body shapes similar to the hesperornithiforms according to graphical analyses; however, Euclidean distance analysis indicates that the Red-necked Grebe is not significantly similar to the three hesperornithiforms in the characters presented, and further indicates that the Western Grebe is significantly similar to the hesperornithiforms when overall body size is removed from consideration. Because the morphology of the Common Loon is significantly similar to Hesperornus regalis, H. gracilis, and Parahesperornis alexi, it is a good model on which to base study of their hind limb musculature and locomotion. Based on this model, Hesperornis, like a loon, likely swam with both feet thrusting backwards simultaneously, avoided land except for nesting, and when forced to move on land, used the same swimming motion to push itself forward slowly. Because of these physical limitations, likely nesting locations may have included protected, vegetated areas such as estuaries, or other locations where the influence of tides and wave action is lessened or buffered.

Rights

Copyright 2006 Francis Nicole Reynaud

Comments

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