An Unusual Lower Cambrian Trilobite Fauna from Nevada GEOLOGICAL SURVEY PROFESSIONAL PAPER 483-F An Unusual Lower Cambrian Trilobite Fauna from Nevada By ALLISON R. PALMER CONTRIBUTIONS TO PALEONTOLOGY GEOLOGICAL SURVEY PROFESSIONAL PAPER 483-F Twelve species representing the Olenellidae, Oryctocephalidae, Ogygopsidae, Dorypygidae, Zacanthoididae^ and Ptychopariidae are described andfigured UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1964 UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director The U.S. Geological Survey Library has cataloged this publication as follows: Palmer, Allison Ralph, 1927- An unusual Lower Cambrian trilobite fauna from Nevada. Washington, U.S. Govt. Print. Off., 1964. iii, 14 p. 3 plates, map, diagr. 30 cm. (U.S. Geological Survey. Professional Paper 483-F) Contributions to' paleontology. Bibliography : p. 12. 1. Trilobites. 2. Paleontology Nevada. 3. Paleontology Cam­ brian. I. Title. (Series) For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, B.C. 20402 CONTENTS Page Abstract.______________-__________________-________-__-__________-_-___----_----_-----__--- Fl Introduction.______________________________-_______________-_______--___-____---__--_------- 1 Systematic paleontology_______-__________________________________-__..___----_---_----------- 2 Olenellidae-- _________________________________________________________________ 2 Dorypygidae.-____-_-___-_-________-__-___-___________-_-_--___-_--_----_--_-------_--- 5 Ogygopsidae_ _ __________________________________________________________________________ 6 Oryctocephalidae.__--_____-_____________________________-______-_____-__--_----_----_-- 7 Zacanthoididae ____-_______-_______________________________-____-____----__-_---------_- 8 Ptychopariidae_________________________________________________________________________ 11 Position uncertain_____________________________________________________________________ 11 References.________________________________________________________________________________ 12 Index_^______________________________________________________________ 13 ILLUSTRATIONS [Plates follow index] PLATE 1. Olenellidae, Oryctocephalidae. 2. Ogygopsidae, Dorypygidae. 3. Zacanthoididae, Ptychopariidae, position uncertain. Page FIGURE 1. Map showing the locality of the fossil collection described in this report. Fl 2. Position of described fauna in regional stratigraphic context-_________ 2 ill CONTRIBUTIONS TO PALEONTOLOGY AN UNUSUAL LOWER CAMBRIAN TRILOBITE FAUNA FROM NEVADA By ALLISON R. PALMER 117° ABSTRACT A fauna of at least 12 species of trilobites, from lower Cam­ brian rocks in Esmeralda County, Nev., constitutes the largest single assemblage of trilobites yet described from Lower Cambrian beds in North America. Well-preserved specimens of the Olenellidae, Oryctocephalidae, Ogygopsidae, Dorypygidae, NYE Zacanthoididae, and Ptychopariidae are present. New taxa include Paedeumias granulatm n. sp.; GoWfieldia pacifica n. gen., n. sp.; Bonn/Id caperata n. sp.; Zacanthopsig contractus n. sp.; ZacantJiopsina eperephes n. gen., n. sp.; and Stephenaspist a/vitus n. sp. INTRODUCTION 37° During reconnaissance geologic mapping of Esmer­ alda County, Nev., J. P. Albers and J. H. Stewart, of the U.S. Geological Survey discovered many localities of fossiliferous Lower Cambrian rocks. Collections from most of these localities were submitted to me for examination. In 1960 a collection from one of these localities (fig. 1) was found to contain an association of nonolenellid trilobites of Middle Cambrian aspect together with undoubted olenellids. In 1961 I was guided to this locality by J. H. Stewart and obtained FIGURE 1. Map showing the locality of the fossil collection de­ a large supplemental collection. That collection is the scribed in this report. principal source of the specimens described here. Lower Cambrian trilobite collections from the West­ beds are about 40 feet above a 45-foot-thick brown ern States rarely contain assemblages of more than half sandstone unit (Stewart, written communication, June a dozen species. Most of the trilobites in any one col­ 1963). The sandy limestones have the characteristics lection are olenellids, although occasionally a simple of a rock type that is found in the lower part of the ptychoparioid or a species of Bonnia or of Zacanthopsis Saline Valley Formation (Nelson, 1962) just above a may be present. Barely are the specimens well pre­ basal sandy or quartzite unit. Nelson subsequently served. Thus, the discovery of an excellently preserved visited this locality and confirmed the identification of Lower Cambrian trilobite assemblage that contains at the fossiliferous beds as the lower part of the Saline least 10 genera representing at least 6 families can be Valley Formation. Nelson also examined stratigra- properly termed unusual. phically important sections in the Last Chance Range, The fossil-bearing beds (USGS Colln.3T48-CO) crop Calif, (fig. 1), in company with J. H. Stewart and me in out in a series of low north-facing hills about 3 miles April 1963. It was determined that the basal quartzites southeast of the junction of Nevada Highways 3 and of the Saline Valley Formation in the northern part of 71 south of Goldfield, Nev., and about 5 miles northeast the range correlate with the Zabriskie Quartzite ex­ of Gold Point in the SWV* sec. 28, T. 6 S., E. 42 E., posed in the southern part of the range. Collections Goldfield (1: 250,000) quadrangle, Nevada. The trilo­ from the upper part of the Saline Valley Formation bites are preserved in dark-gray limestone beds less than have yielded species of the olenellid genus BristoUa. 6 inches thick that are characterized by well-rounded This is a characteristic and locally abundant genus in the grains of quartz sand "floating" in the limestone matrix Lower Cambrian part of the Carrara Formation, which or concentrated in the lower part of the beds. These is above the Zabriskie Quartzite, in the Death Valley Fl CONTRIBUTIONS TO PALEONTOLOGY region. Thus, the fauna described here from the lower (1948) from the Lower Cambrian of Quebec and re­ part of the Saline Valley Formation seems firmly estab­ ported by him (Easetti, 1951) from the Lower Cambrian lished in the upper part of the Lower Cambrian in a of British Columbia, are absent from this assemblage. position slightly older than that yielding the Bristolia Sampling of the Lower Cambrian faunas of the West­ fauna (fig. 2). ern States has just begun, however, and an increase in our knowledge of these older trilobite faunas can be anticipated. Last Chance Death Valley Range region SYSTEMATIC PALEONTOLOGY v/vs/vVWvVVvV The descriptive terminology used for the olenellids Vw^VV^tyv/yyv^/ Lower lime­ is the same as that used earlier by me. (See Palmer, Mule stone member 1957.) Descriptive terminology for the other trilobites Spring Limestone is that found in the illustrations or glossary of the _ Bristol/a _ Treatise on Invertebrate Paleontology, Part O, Arthro- poda 1 (Harrington and others, 1959). Familial or Carrara generic assignments that have no comment indicate Saline Formation Valley acceptance of the classification in the treatise. Local­ Formation Fauna described ity data and identifying locality numbers for figured /in this report specimens are recorded in the Cambrian-Ordovician locality catalog of the U.S. Geological Survey. All figured specimens, unless otherwise indicated, are from Basal Zabriskie U.S. Geological Survey collection 3748-CO. sandy member Quartzite An/UlWVM AnWuVMA Order REDLICHIIDA Bichter Family OLENELLIDAE Vogdes Genus PAEDETJMIAS Walcott FIGURE 2. Correlation of parts of the Lower Cambrian for- mational sequences between the Last Chance Range and Paedeumias Walcott, 1910, p. 304; Resser, 1928, p. 4; Poulsen, the Death Valley region, California, showing the approxi­ 1932, p. 26; Resser and Howell, 1938, p. 225; Poulsen, 1959, mate stratigraphic position of the fauna described in this report. p. 192. Type species. Paedeumias transitans Walcott, 1910, This trilobite assemblage cannot be compared at pres­ p. 305, pi. 34, fig. 1. ent with any other known assemblage in the Cordil- Diagnosis. Olenellidae having glabella distinctly leran region of North America. Lower Cambrian as­ separated from cephalic 'border by preglabellar field semblages, which include various nonolenellids but but generally connected to border by narrow median fewer total species, have been described by Easetti ridge. Cephalic border wirelike. Palpebral lobes (1948) from boulders in the Levis conglomerates of long; line connecting posterior tips crosses glabella Quebec and by Eesser (1938) from limestones of the posterior to midlength of preoccipital segment. In- Austinville district, Virginia; but the fauna described tergenal spines short and directed nearly straight here is by far the largest and most varied assemblage of posteriorly in mature holaspids; near genal spines. Lower Cambrian trilobites yet described from North Discussion. Walcott originally diagnosed Paedeu­ America. Entirely new forms are Zacanthopsina mias as a genus differing from Olenellus by having eperephes n. gen., n. sp., and Stephenaspis ? avitus n. sp. thoracic segments posterior to the spine-bearing 15th Typical Lower Cambrian species include Paedewnias segment. Eesser (1928) correctly referred one of granulatus n. sp., Wanneria cf. W. walcottana (Wan­ Walcott's best paratypes (Walcott, 1910, pi. 33, fig. 1) ner) , Zacanthopsis