Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

Journal of Paleontology

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by VENDRASCO, M. J. Articles by RUNNEGAR, B. Search for Related Content GeoRef GeoRef Citation

LATE CAMBRIAN AND EARLY ORDOVICIAN STEM GROUP CHITONS (MOLLUSCA: POLYPLACOPHORA) FROM UTAH AND MISSOURI

¹ Department of Earth and Space Sciences, University of California, Los Angeles 90095-1567, <mikev{at}ess.ucla.edu>

Abundant silicified shell plates (valves) of some of the oldest-known chitons were recovered from the Late Cambrian Notch Peak Formation of Utah. The chiton fauna is dominated numerically by Matthevia wahwahensis new species, but also includes another mattheviid, Eukteanochiton milleri new genus and species, and a preacanthochitonid, Orthriochiton utahensis new genus and species. Robustum from the Early Ordovician Gasconade Formation of Missouri is herein reinterpreted as a septemchitonid chiton, and Hemithecella, from the Late Cambrian-Early Ordovician of the eastern United States, is once again considered a mattheviid chiton. Mattheviid valves are unique among chitons in that they are massive, elongate, and contain one or two tunnels; these characteristics have led some to exclude this family from the Polyplacophora. However, mattheviids and other chitons share many valve characters, including granules, an apical shelf, a thin anterior margin, bilateral symmetry, three valve types, and a shell layer perforated with canals. Furthermore, recently described chiton valves from the Silurian of Gotland, the Ordovician of Wisconsin, and the Cambrian-Ordovician of Missouri are gradational between the Notch Peak mattheviid valves and those of younger polyplacophorans. Also, Matthevia wahwahensis n. sp. has valves with a flat apical area, allowing for valve overlap, and so provides a link between the unusual chiton Matthevia variabilis, which had nonoverlapping, spiky valves, and Chelodes, a less disputed chiton. Known fossil assemblages reveal that, along the coastline of Laurentia during the Cambrian-Ordovician, chitons were diverse, consisting of at least four families and with much variation in valve shape.

This article has been cited by other articles:

				J. D Sigwart and M. D Sutton Deep molluscan phylogeny: synthesis of palaeontological and neontological data Proc R Soc B, October 7, 2007; 274(1624): 2413 - 2419. [Abstract] [Full Text] [PDF]

				J. POJETA JR., J. F. TAYLOR, and G. DARROUGH MATTHEVIA (POLYPLACOPHORA) INVADES THE ORDOVICIAN: THE FIRST REPORTED POST-CAMBRIAN OCCURRENCE Journal of Paleontology, September 1, 2005; 79(5): 1021 - 1027. [Full Text] [PDF]