Lucas (2002) has criticized our tentative correlation of the North American Chickasha Formation with Russian continental strata that date from the late Kazanian (Reisz and Laurin, 2001) and argued instead, on the basis of marine biostratigraphic and magnetostratigraphic evidence, that the Chickasha Formation is substantially older than the Late Kazanian and likely Leonardian in age. We would like to comment on some of his statements and then discuss their implications. There is no magnetostratigraphic evidence (in Oklahoma) that the Chickasha is substantially older than the Russian Kazanian. Lucas's argument is based on his interpretation of the age of the...

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