The graptolites " Pristiograptus " praedeubeli (Jaeger) and " Pristiograptus " ludensis (Murchison) (uppermost Wenlock, Silurian) from Arctic Canada: taxonomy and evolution

• Published in: Canadian Journal of Earth Sciences
• Main Author: Lenz, Alfred C.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1994
• Subjects: General Earth and Planetary Sciences; Arctic; Canada; Murchison
• Online Access: http://dx.doi.org/10.1139/e94-125; http://www.nrcresearchpress.com/doi/pdf/10.1139/e94-125

Isolated, uncompressed specimens of Pristiograptus dubius, "Pristiograptus" praedeubeli, and "Pristiograptus" ludensis are described from Arctic Canada. Pristiograptus dubius and early forms of "P." praedeubeli are very similar, suggesting a respective, ancestor-descendant relationship. The study shows that "P." praedeubeli and "P." ludensis are generally readily distinguishable, but that the sicular region of the latter shows a much greater variation than previously recognized. End member morphs of "P." ludensis are remarkably similar to "P." deubeli, further confirming a close evolutionary link between them. To facilitate refined biostratigraphic division of the uppermost Wenlock, therefore, large collections of specimens are required to separate those two species when co-occurring.