New Early Cambrian olenelline trilobites from the Sekwi Formation, Mackenzie Mountains, Northwest Territories, Canada, and new insights into olenellinid evolutionary history and biogeography.

摘要

The olenellinid trilobites of the Early Cambrian are a diverse clade that has been an ideal group used in phylogenetic analyses. Recently, new specimens from the Sekwi Formation of the Mackenzie Mountains, Northwest Territories, Canada, were collected to add more material, to help paleontologists to better understand this group. This thesis presents three new species of Bradyfallotaspis and one new species of Nevadia. Further, new specimens of Nevadia ovalis expand the known geographic range for this species, only known previously from a locality in Senora, Mexico. This expansion is unusual for olenellinid trilobites, which generally have very restricted ranges. A phylogenetic analysis of Judomia absita was performed to help ameliorate confusion regarding its generic assignment between Judomia and Paranevadella, providing further support for a close biogeographic relationship between Laurentia and Siberia.