Trilobites of the Upper Cambrian Dunderberg Shale Eureka District, Nevada By ALLISON R. PALMER SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY GEOLOGICAL SURVEY PROFESSIONAL PAPER 334-C Fifty-three species of trilobites representing genera are described and illustrated UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1960 UNITED STATES DEPARTMENT OF THE INTERIOR FRED A. SEATON, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director For sale by the Superintendent of Documents, U.S. Government Printing Office Washington 25, D.C. - Price 65 cents (paper cover) CONTENTS Page Systematic paleontology Continued Abstract...___________________________ 53 Ptychoparioidea Continued Page Introduction __________________________ 53 Pterocephaliidae.. _ _________________________ 80 Acknowledgments. -___-.______--_____-_ 55 Aphelaspidinae_ -_-_--____--____________ 80 Stratigraphy._________________________ 55 Litocephalus--- ______________________ 81 Taxonomic procedure__________________ 57 Taenora- _____--.-__--_____-_-__.__ 83 Terminology __________________________ 59 Pterocephaliinae. _______________________ 84 Hypostome morphology and identification. 60 Cernuolimbus-- __-__-__-____-_-_.___ 84 Systematic paleontology.___-_-_-___-_._ 61 Pterocephalia- ______________________ 86 Agnostidea_ _ ____._-_____--___.__ 61 Sigmocheilus _______________________ 89 Ptychoparioidea unassigned. _____________________ 92 Angostidae___________________ 61 Anechocephalus _________-___------__--______ 92 Pseudagnostus_ ___________ 61 Bynumiella, ______--__---___-_-_-_-_----_-_. 93 Homagnostus ______________ 62 Bynumina--------------------------------- 93 Phalacroma. ______________ 63 Cheilocephalus------------------------------ 94 Ptychoparioidea_ _ _________________ 64 Dokimocephalus_ _ _________________________ 95 Elviniidae ___----___-________- 64 Iddingsia---------------------------------- 95 Dunderbergia- _____________ 65 Kindbladia.-------------------------------- 97 Elburgia- _________________ 68 Minupeltis--------------------------------- 98 Elvinia ___________________ 70 Morosa------------------------------------ 98 Elviniella- ________________ 71 Oligometopus------------------------------- 100 Pinctus.----------------------------------- 100 Irvingella ___--_____-__-.__ 72 Pseudosaratogia----------------------------- 101 Housiidae____ ___--_-______ ____ 74 Genus and species undetermined l_____--_____- 101 Housia- -___-_-___-_______ 74 Genus and species undetermined 2_____________ 102 Parahousia- _______________ 76 Genus and species undetermined 3_____-------- 102 Prehousia- ________________ 77 Locality information, __________-___-__--__-----_--__ 102 Olenidae_ _____________________ 78 References cited____________-_-_--____-_.------_---_ 103 OlenusC?)-------- -----__-- 79 Index,_-___-_-----_---------_-----------------_--- 107 ILLUSTRATIONS [Plates 4-11 follow page 110] PLATE Agnostidae and Elviniidae. Elviniidae. Elviniidae and Olenidae. Housiidae and Aphelaspidinae. Pterocephaliinae, Aphelaspidinae, and Anechocephalus. 9. Pteroceph aliinae. 10. Pterocephaliinae and unassigned genera. 11. Unassigned genera and Hypostomes. FlGTRE 5. Map showing relations of the Eureka district to other localities in the Great Basin with Dunderberg faunas______ 54 6. Map showing location of measured section through Dunderberg shale___-_____- ______-______-_____--_--__ 55 Ranges of trilobites in the Dunderberg shale ------------------------------------------------------------ 57 Comparison of the ventral courses of the cephalic sutures in some Late Cambrian trilobites. A, Pterocephalia. B, Housia. C. Dunderbergia. D, Prehousia. E, Aphelaspis------------------------------------------ 64 9. Dunderbergia polybothra n. sp____________________-___________________-__-------------------_---___----- 65 10. Elburgia quinnensis (Resser)_____________________-_________________________--__--_-__-___-_----------- 68 11. Eli'inin roemeri (Shiunard)________________________________________-_--_---__--------__---------_----- 70 12. Housia ovata n. sp_________________________________________________--__---_-___----__-_-_------------- 75 13. Parahousia constricta n. sp________________________________________________-_______-___------------_--_ 76 14. Prehousia alata n. sp_____________________________ ________________________-_---_--_-__--------------- 77 15. Olenus(?) wilsoni Heniiingsmoen__ _______ 79 16. Litocephalus bilobatus (Hall and Whitfield. 81 17. Taennra expansa n. sp_ ______ ^ __________ 83 18. Cernuolimbus orygmatos n. sp______ ______ 85 19. Pterocephalia sanctisabae Roemer _______ 86 20. Sigmocheilus serratus n. sp _____________ 89 21. Bynumiella? acuminata 11. sp____________ 93 22. Rlorosa longispina n. sp_________________ 99 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEW. DA By ALLISON R. PALMER ABSTRACT more resistant Hamburg dolomite and is overlain, also The Dunderberg shale in the Eureka district is the north- conformably, by the generally cherty Catlin member westernmost expression of a relatively thin nonresistant unit of the Windfall formation (Nolan and others, 1956). (100-300 ft thick) of interbedded shale and fossiliferous lime­ A similar fossiliferous nonresistant unit of interbed­ stone of Late Cambrian age lying between generally less fos­ ded limestone and shale with approximately the earne siliferous and more resistant carbonate units in southeastern Nevada and adjacent parts of Utah and California. Five local relation to adjacent carbonate units is present in al­ lithic units, designated by letter and beginning at the base most every Upper Cambrian sequence of rocks south with a shale unit (A), are recognized within the Dunderberg of the 40th parallel in southern Nevada and adjacent shale. Overlying units alternate in dominance between lime­ parts of Utah and California (Palmer, 1956b). De­ stone and shale. All but the upper unit (E) contain thin fos­ spite the apparent extensive geographic distribution siliferous limestones bearing generally distinctive trilobite as­ semblages. Ranges of many common species are sufficiently of the Dunderberg shale or correlative lithic units restricted so that isolated collections from structurally dis­ (over 250,000 square miles) (fig. 5) and the gener­ rupted areas within the Eureka district can be placed within ally fossiliferous nature of the Dunderberg, less than 20 to 40 feet of their original stratigraphic position within the 30 species of trilobites in its large fauna have been upper or lower parts of the Dunderberg shale. The fauna of units A-C belongs to the upper half of the Dunderbergia zone described. of late Dresbach age. The fauna of unit D correlates with The earliest descriptions of trilobites from the Dun­ the basal part of the Elvinia zone of early Franconia age. The derberg shale are by Hall and Whitfield (1877) and presence of Homagnostus obesus (Belt) and Olenusl wilsoni Walcott (1884). Since these publications, only occa­ Henningsmoen in units A and B indicates a correlation of sional references have been made to Dunderberg trilo­ these beds with the Olenus and If. obesus zone in the early Late Cambrian section of the Scandinavian region. bites principally as nomenclatural changes or brief Fifty-three species representing 32 genera are described. The descriptions of new forms in large regional faunal pa­ following new taxa are named: Subfamily Aphelaspidinae (of pers (Walcott, 1916, 1924, 1925; Kesser, 1935, 1936, the family Pterocephaliidae); Genera Elburgia, Elviniella, Pre- housia, Parahousia, Cernuolimbus, Sigmocheilus, Taenora, Alinu- 1937, 1942; Palmer, 1955). The purpose of this- pa­ peltis, Morosa, Anechocephalus; and species, Dunderbergia per is to describe the trilobites of the Dunderberg bigranulosa, D. polybothra, Elviniella laevis, Prehousia semi­ shale in its type area and to document as precisely as circular is, P. alata, Parahousia constricta, Housia ovata, Cernuo­ possible the stratigraphic distribution of the described limbus semigranulosus, C. orygmatos, C. depressus, Pterocephalia concava, P. elongata, Litocephalus verruculapeza, L. granulo- fossils within the unit. marginatus, Taenora. expansa, Sigmocheilus serratus, Minupeltis The bulk of the material examined during this study conservator, Morosa longispina, Bynumiellal acuminata, Anechoce­ came from collections by C. D. Walcott, and geolo­ phalus trigranulatus, Pseudosaratogia leptogranulata, and P. abnorrnis. Evidence is shown that primary species characteris­ gists of the 40th parallel survey in the late 1800's; tics are to be found in the external ornament of the exoskeleton. collections by the late Josiah Bridge and G. A. Cooper Genera are composed of species sharing nearly common shape in 1939; and collections by the writer in 1951 and but differing consistently in characteristics such as external ornament. Emphasis in family groupings is placed on structure 1957. of the glabella, frontal area, and pleural parts of the pygidium. The collections in 1951 and 1957 were obtained from Application and elaboration of the principles for grouping trilo- the section in Windfall Canyon chosen by Nolan and bites into genera and families are illustrated particularly with others (1957, p. 19) as the most complete and un­ regard to the families Elviniidae, Housiidae, and Pterocephaliidae. broken section of the Dunderberg shale in the Eureka INTRODUCTION district (fig. 6). Each collection was obtained from a The Dunderberg shale is a relatively nonresistant single bed and