MEMOIR 2 Studies of the Actinoceratida I. The Ordovician Development of the Actinoceratida, With Notes on Actinoceroid Morphology and Ordovician Stratigraphy II. Macroloxoceras, a Devonian Homeomorph of the Actinoceratida By ROUSSEAU H. FLOWER 1 9 5 7 STATE BUREAU OF MINES AND MINERAL RESOURCES NEW MEXICO INSTITUTE OF MINING AND TECHNOLOGY CAMPUS STATION SOCORRO, NEW MEXICO NEW MEXICO INSTITUTE OF MINING & TECHNOLOGY E. J. Workman, President STATE BUREAU OF MINES AND MINERAL RESOURCES Alvin J. Thompson, Director THE REGENTS MEMBERS EX OFFICIO The Honorable Edwin L. Mechem ................................................ Governor of New Mexico Mrs. Georgia L. Lusk ......................................................... Superintendent of Public Instruction APPOINTED MEMBERS Robert W. Botts ................................................................................................ Albuquerque Holm 0. Bursum, Jr. ............................................................................................... Socorro Thomas M. Cramer .................................................................................................. Carlsbad John N. Mathews, Jr. ................................................................................................ Socorro Richard A. Matuszeski ..................................................................................... Albuquerque Published December 31, 1957 Contents PART I THE ORDOVICIAN DEVELOPMENT OF THE ACTINOCERATIDA, WITH NOTES ON ACTINOCEROID MORPHOLOGY AND ORDOVICIAN STRATIGRAPHY Page ABSTRACT .......................................................................................................................................... 3 INTRODUCTION ................................................................................................................................ 3 ACKNOWLEDGMENTS ..................................................................................................................... 4 MORPHOLOGICAL NOTES ............................................................................................................... 5 STRATIGRAPHIC SUMMARY OF THE ACTINOCEROIDS IN THE ORDOVICIAN .. 7 North America .................................................................................................................................. 7 Whiterock ...................................................................................................................................... 7 Chazy ............................................................................................................................................ 7 Black River ................................................................................................................................... 7 Trenton .......................................................................................................................................... 8 East-Central region ....................................................................................................................... 8 Appalachian region ....................................................................................................................... 9 Red River faunas ........................................................................................................................... 9 Richmond faunas ........................................................................................................................ 10 Northern Europe .............................................................................................................................. 11 Eastern Asia ..................................................................................................................................... 11 EVOLUTION OF THE ACTINOCERATIDA ................................................................................... 12 Previous views ................................................................................................................................ 12 Primitive features ............................................................................................................................ 12 Ancestry of the Actinoceratida ........................................................................................................ 13 Evolution within the Actinoceratida ............................................................................................... 14 NOTES ON ORDOVICIAN CORRELATIONS ................................................................................ 17 THE MONTOYA GROUP .................................................................................................................. 20 SYSTEMATIC DESCRIPTIONS ....................................................................................................... 23 Genus POLYDESMIA Lorenz ........................................................................................................ 23 Genus WUTINOCERAS Shimizu and Obata (1936) ..................................................................... 23 Genus NYBYOCERAS Troedsson (1926) ..................................................................................... 23 Nybyoceras montoyense Flower, n. sp. ....................................................................................... 24 Genus ADAMSOCERAS Flower, n. gen. ...................................................................................... 25 Adamsoceras isabelae Flower, n. sp. .......................................................................................... 25 Page Genus ORMOCERAS Stokes .............................................................................................. 26 Ormoceras neumani Flower, n. sp. ................................................................................................ 27 Ormoceras dartoni Flower, n. sp. ..................................................................................... 27 Genus DEIROCERAS Hyatt ............................................................................................................ 29 Deiroceras, sp. .............................................................................................................................. 29 Genus ACTINOCERAS Bronn ............................................................................................ 30 Group of Actinoceras margaretae ...................................................................................................... 30 Group of Actinoceras ruedemanni ..................................................................................... 30 Group of Actinoceras centrale ......................................................................................... 31 Group of Actinoceras paquettense .................................................................................... 31 Group of Actinoceras winstoni ............................................................................................................ 32 Group of Actinoceras simplicem ......................................................................................................... 32 Group of Actinoceras anticostiense .................................................................................................... 32 Inadequately known species ......................................................................................................... 33 Arctic species ............................................................................................................................... 33 Asiatic species .............................................................................................................................. 34 Actinoceras margaretae Flower, n. sp. .......................................................................................... 34 Actinoceras aequale Flower, n. sp. ................................................................................................ 35 Actinoceras gradatum Flower, n. sp. ................................................................................ 36 Actinoceras sinclairi Flower, n. sp. .................................................................................. 37 Actinoceras huronioides Flower, n. sp. ............................................................................. 37 Actinoceras mutabile Flower, n. sp. ............................................................................................... 38 Actinoceras abortivum Flower, n. sp. ................................................................................ 39 Actinoceras winstoni Flower, n. sp. .............................................................................................. 39 Actinoceras incantatum Flower, n. sp. ........................................................................................... 40 Genus LEURORTHOCERAS Foerste ............................................................................................. 41 Genus KOCHOCERAS Troedsson .................................................................................................. 43 Genus ARMENOCERAS Foerste .................................................................................................... 44 Armenoceras callaghani Flower, n. sp. .......................................................................................... 44 Armenoceras lenticontractum Flower, n. sp. .................................................................................. 45 Armenoceras australe Flower, n. sp. ............................................................................................