The brachymetopid trilobite Radnoria in the Silurian (Wenlock) of New York State and Arctic Canada

• Published in: Canadian Journal of Earth Sciences
• Main Authors: Adrain, Jonathan M, Tetreault, Denis K
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2005
• Subjects: General Earth and Planetary Sciences; Arctic; Nunavut; Canada; Cape Phillips
• Online Access: http://dx.doi.org/10.1139/e05-085; http://www.nrcresearchpress.com/doi/pdf/10.1139/e05-085

Radnoria bretti n. sp., from the Wenlock (Sheinwoodian) Rochester Formation of western New York State, is the best preserved and most completely known member of its genus. It provides the first definitive information on Radnoria's hourglass-shaped rostral plate, the first known hypostome of a Silurian member of the genus, demonstrates that Radnoria engaged in sphaeroidal enrollment, and reveals that early holaspid individuals had tubercles on the posterior thoracic axes and pygidial axial rings that were effaced with maturity. Three new species from the Wenlock of the Cape Phillips Formation of Nunavut are known from sparse material and are reported in open nomenclature. Together, the species greatly increase knowledge of Laurentian Silurian brachymetopids, which have until now been known from a single cranidium from the Wenlock of Arkansas.