Revised Biostratigraphy, Systematics, and Paleobiogeography of the Trilobites from the Middle Cambrian Nelson Limestone, Antarctica

Abstract

Abstract.-A biostratigraphic analysis of the Nelson Limestone, Neptune Range, Antarctica based on the distribution of trilobites in measured sections suggests that the age of the formation is probably late Floran to Undillan; the possibility of a Boomerangian age is considered less likely. The Nelsonia schesis and A mphoton oatesi zones are also defined. Paleobiogeographic analysis of trilobites in the Nelson Limestone using parsimony analysis of endemism (PAE) suggests that the Neptune Range and other parts of East Antarctica share the closest biogeographic area relationships with Australia rather than with northern Victoria Land or West Antarctica. This may have implications for the tectonic assembly of Antarctica. New specimens of previously described trilobite species from the Nelson Limestone include two new species, Peishania? neptunensis and Poriagraulos kaesleri. One species, Dorypyge sp. cf. D. australis, previously known only from the Bowers Terrane of northern Victoria Land, Antarctica, is recognized for the first time in the Neptune Range.