MINNESOTA GEOLOGICAL SURVEY Harvey Thorleifson, Director A RESTUDY OF THE LATE CAMBRIAN MOLLUSCAN FAUNA OF BERKEY (1898) FROM TAYLORS FALLS, MINNESOTA Ellis L. Yochelson Gerald F. Webers National Museum of Natural History Macalester College Report of Investigations 64 ISSN 0076-9177 Saint Paul — 2006 A RESTUDY OF THE LATE CAMBRIAN MOLLUSCAN FAUNA OF BERKEY (1898) FROM TAYLORS FALLS, MINNESOTA This publication is accessible from the home page of the Minnesota Geological Survey (http://www.geo.umn.edu/mgs) as a PDF file readable with Acrobat Reader 5.0. Date of release: December, 2006 Recommended citation Yochelson, E.L., and Webers, G.F., 2006, A restudy of the Late Cambrian Molluscan fauna of Berkey (1898) from Taylors Falls, Minnesota: Minnesota Geological Survey Report of Investigations 64, 60 p. 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CONTENTS page ABSTRACT .............................................................................................................................................1 INTRODUCTION ..................................................................................................................................1 STRATIGRAPHIC SETTING AND GEOLOGIC AGE .................................................................2 AVAILABLE MATERIAL AND SIGNIFICANCE ............................................................................5 PALEOECOLOGICAL SPECULATION ............................................................................................6 A BRIEF ESSAY ON THE CLASSIFICATION OF EARLY PALEOZOIC MOLLUSCA, AND PARTICULARLY GASTROPODA, IN NORTH AMERICA OVER ELEVEN DECADES ............................................................................................................................................7 Mollusca in the late nineteenth and early twentieth centuries .......................................8 The concept of Monoplacophora—to the mid-twentieth century ...................................9 The 1950s and the 1960s ...........................................................................................................10 The 1970s and the 1980s ...........................................................................................................11 The last decade of the twentieth century and the start of the twenty-first century .....13 MUSCLE SCARS AND ORIENTATION OF SPECIMENS ...........................................................16 THE CLASS GASTROPODA ..............................................................................................................18 THE CLASS TERGOMYA ....................................................................................................................18 A SURVEY OF EARLIER DESCRIBED NORTH AMERICAN LATE CAMBRIAN– EARLY ORDOVICIAN TERGOMYA SPECIES ..........................................................................22 SYSTEMATIC PALEONTOLOGY .....................................................................................................24 Class Gastropoda Cuvier .........................................................................................................24 Class Tergomya Horny .............................................................................................................28 Class ?Helcionelloidea ..............................................................................................................45 SUPPLEMENT TO SYSTEMATIC PALEONTOLOGY ..................................................................47 Class Gastropoda ......................................................................................................................47 STRATIGRAPHIC MATTERS ............................................................................................................48 SPECULATIVE MATTERS ..................................................................................................................49 Disparity and diversity ............................................................................................................49 Muscles and other presumed soft parts ................................................................................50 Symmetrical and asymmetrical shell forms ........................................................................51 Class-level evolution within the Mollusca ..........................................................................52 High-level evolution within the Mollusca ..........................................................................53 ACKNOWLEDGMENTS .....................................................................................................................53 REFERENCES .........................................................................................................................................54 APPENDIX ..............................................................................................................................................60 FIGURES Figure 1 Geologic map of the St. Croix River valley .......................................................................................... 2 Figure 2 Nomenclature .......................................................................................................................................... 3 Figure 3 Gastropoda and Tergomya ..................................................................................................................... 26 Figure 4 Tergomya .................................................................................................................................................. 30 iii Figure 5 Tergomya, ?Proplina convexum (Berkey) .............................................................................................33 Figure 6 Kirengella stabilis Berkey ........................................................................................................................35 Figure 7 Tergomya, ?Kirengella rectilateralus (Berkey) ......................................................................................36 Figure 8 Tergomya, Hypseloconus elongatus Berkey ..........................................................................................38 Figure 9 Tergomya, ?Hypseloconus cylindricus Berkey .....................................................................................43 Figure 10 ?Proteroconus capuloides (Berkey) .........................................................................................................44 Figure 11 New genus and ?"Cloudia" sp. ............................................................................................................46 NOTE ON MEASUREMENTS USED IN THIS REPORT Although the metric system is preferred in scientific writing, certain measurements are still routinely made in English customary units; for example, distances on land are measured in miles and depths in drill holes are measured in feet. Preference was given in this report to retaining the units in which measurements were made. To assist readers, conversion factors for some of the common units of measure are provided below. English units to metric units: To convert from to multiply by inch millimeter 25.40 inch centimeter 2.450 foot meter 0.3048 mile kilometer 1.6093 Metric units to English units: To convert from to multiply by millimeter inch 0.03937 centimeter inch 0.3937 meter foot 3.2808 kilometer mile 0.6214 iv A RESTUDY OF THE LATE CAMBRIAN MOLLUSCAN FAUNA OF BERKEY (1898) FROM TAYLORS FALLS, MINNESOTA Ellis L. Yochelson, deceased Gerald F. Webers, Macalester College, St. Paul, Minnesota ABSTRACT The molluscan fossils described and illustrated by C.P. Berkey from Upper Cambrian rocks at Taylors Falls, Minnesota, are redescribed and printed in this report. They comprise rare Gastropoda and relatively abundant and diverse Tergomya. The latter are supplemented by a few additional specimens collected decades ago. Palmer's reexamination of trilobite specimens collected by Berkey indicates an Elvinia age for the fauna. We conclude that the species differentiated by Berkey (1898) are mostly well founded. Berkey's study was significant because it documented the diversity of Mollusca in nearshore sandstones of Cambrian age. To place this nineteenth century paper in context, included herein is a summary of the changing views on evolution of portions of molluscan classification and a survey of some of the older-named, early Paleozoic, North American bilaterally symmetrical univalve species. INTRODUCTION He also included photographs of a few specimens. Although Berkey's effort of producing photographs When C.P. Berkey was a geology graduate student of fossils at that time is commendable, unfortunately at the University of Minnesota, he made a geologic they add little to the understanding of the taxa. His map, interpreted the topography and glacial geology, few general remarks in the text indicate a grasp and described the lithology of sedimentary and of the literature, and he had a clear concept of the igneous rocks he encountered