Earth Sciences

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By virtue of our outstanding location in the scenic and rugged mountains of southwest Montana, Earth Science students have many opportunities to participate in field trips that will facilitate the study of earth processes, earth resources, earth history, and environments that people have modified. These field trips are an integral part of many courses, as well as extracurricular activities sponsored by the department. Fieldwork is a very important component of our instructional programs at both the undergraduate and graduate levels.Because of the research conducted by faculty in the department, an undergraduate student may have the opportunity to work on active research projects. In particular, we offer the opportunity to do a "Senior Thesis" to our top students in each senior class. The senior thesis enables a student to work on an actual research project under the supervision of a faculty member, write a research report (a mini-thesis), and present the results at a professional conference. This is excellent preparation for graduate school and/or the workplace. Our Master's theses frequently involve field-testing of state-of-the-art hypotheses proposed elsewhere, as well as formulation of the next generation of hypotheses, which will shape our disciplines in the decades to come. Most Master's thesis work in the Department is published in the peer-reviewed professional literature after presentation at regional or national professional meetings.

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Author: search.filters.author.Legendre, Lucas J.Subject: search.filters.subject.hard-shelled

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    The diverse terminology of reptile eggshell microstructure and its effect on phylogenetic comparative analyses
    (Wiley, 2022-06) Legendre, Lucas J.; Choi, Seung; Clarke, Julia A.
    Reptile eggshell ensures water and gas exchange during incubation and plays a key role in reproductive success. The diversity of reptilian incubation and life history strategies has led to many clade-specific structural adaptations of their eggshell, which have been studied in extant taxa (i.e. birds, crocodilians, turtles, and lepidosaurs). Most studies on non-avian eggshells were performed over 30 years ago and categorized reptile eggshells into two main types: “hard” and “soft” – sometimes with a third intermediate category, “semi-rigid.” In recent years, however, debate over the evolution of eggshell structure of major reptile clades has revealed how definitions of hard and soft eggshells influence inferred deep-time evolutionary patterns. Here, we review the diversity of extant and fossil eggshell with a focus on major reptile clades, and the criteria that have been used to define hard, soft, and semi-rigid eggshells. We show that all scoring approaches that retain these categories discretize continuous quantitative traits (e.g. eggshell thickness) and do not consider independent variation of other functionally important microstructural traits (e.g. degree of calcification, shell unit inner structure). We demonstrate the effect of three published approaches to discretizing eggshell type into hard, semi-rigid, and soft on ancestral state reconstructions using 200+ species representing all major extant and extinct reptile clades. These approaches result in different ancestral states for all major clades including Archosauria and Dinosauria, despite a difference in scoring for only 1–4% of the sample. Proposed scenarios of reptile eggshell evolution are highly conditioned by sampling, tree calibration, and lack of congruence between definitions of eggshell type. We conclude that the traditional “soft/hard/semi-rigid” classification of reptilian eggshells should be abandoned and provide guidelines for future descriptions focusing on specific functionally relevant characteristics (e.g. inner structures of shell units, pores, and membrane elements), analyses of these traits in a phylogenetic context, and sampling of previously undescribed taxa, including fossil eggs.
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