DOI

10.17077/etd.5fda-79p2

Document Type

Thesis

Date of Degree

Summer 2019

Degree Name

MS (Master of Science)

Degree In

Geoscience

First Advisor

Adrain, Jonathan M.

First Committee Member

Stephen R. Westrop

Second Committee Member

Cramer, Bradley D.

Abstract

The Laurentian trilobite genus Clelandia Cossmann, 1902, is represented by 12 named species that range from the late Cambrian to Early Ordovician. Species of Clelandia have been described from many localities in the United States, Canada, Scotland, and Greenland and attempts have been made to employ them as tools in biostratigraphic correlation. Nevertheless, important questions persist regarding the taxonomy and phylogeny of the group. No species-level phylogenetic analysis has been attempted for the genus and its family affinity has been unclear. Previous work often has produced limited numbers of small photographs which tend to mask subtle, but critical, morphological details and confuse taxonomic identification.

New collections from the Great Basin of the western United States have resulted in material representing five new species of Clelandia, three of which are formally named. Other species of Clelandia are illustrated and the type species is redescribed. C. aspina and C. bispina are reported from a new locality in east-central Nevada. The first articulated specimens from a species of Clelandia are illustrated and demonstrate multiple synapomorphies of the thorax and pygidium that strongly indicate a unique, low-diversity clade of trilobites which persisted from the late Cambrian into the Early Ordovician with similarities to the Kingstoniidae. Phylogenetic analysis shows Clelandia to contain two distinct components. One component is characterized by species with glabellar furrows, widely flared posterior projections, and exsagittal pits of the occipital furrow. A more derived component consists of species with long glabellar spines, relatively narrow posterior fixigenae, bacculae, and a unique glabellar-occipital spine structure.

Keywords

cladistics, Nevada, silicified, systematics, trilobite, Utah

Pages

xxii, 254 pages

Bibliography

Includes bibliographical references (pages 236-254).

Comments

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Copyright

Copyright © 2019 Reuben Yanwei Ng

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Geology Commons

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