Trilobites of the Late Cambrian Pterocephaliid biomere in the Great Basin, United States

Abstract

The Pterocephaliid biomere is a biostratigraphic unit of stage magnitude that includes the most consistently fossiliferous parts of the Upper Cambrian in the Great Basin of western conterminous United States. The thickness of strata containing faunas of this biomere generally exceeds 500 feet. This interval includes units consisting of fine-grained detrital material and of clean carbonate rocks; the carbonate rocks probably represent sediments that composed a broad carbonate bank, and the units of detrital material represent belts of predominantly land-derived detrital sediments that flanked the bank on the east and west. The ptychoparioid trilobite fauna of the Pterocephaliid biomere consists of 112 species representing 51 genera. The sequence of faunas within the Pterocephaliid biomere is divided into five zonal assemblages that can be traced throughout the Great Basin. The assemblages are, in ascending order, the A.phelaspis zone, D•icanthopyge zone, Prehousia zone, Dunderbergia zone, and Elvinia zone. The first three zones, which are valid throughout the Great Basin, may correlate with beds currently assigned only to the Aphelaspis zone in central Texas and the southern Appalachian region. The principal faunal elements of the Pterocephaliid biomere probably invaded the Great Basin region from oceanic regions to the west and annihilated nearly all previously existing faunas of the older Crepicephalid biomere. The invading faunas then evolved in place and were in turn annihilated by a new invading fauna, which terminated the Pterocephaliid biomere. Several possible evolutionary series are described, including one that extends through five species and two genera. Geographic distribution of contemporaneous ornamented species in several genera suggests some correlation between environment and ornamentation in some groups of trilobites. New taxa are Oligometopus contractus n. sp., Oheilocephalus brachyops n. sp., Oheilocephalus granulosus n. sp., Pseudokingstonia exotica n. gen., n. sp., Iddingsia intermedia n. sp., Apachia prima n. sp., Dellea? punctata n. sp., Dunderbergia calculosa n. sp., Dunderbergia brevispina n. sp., Elburgia intermedia n. sp., Irvingella transversa n. sp., H ardyoides mimicus n. sp., Aciculolenus peculiaris n. gen., n. sp., Xenocheilos granulosus n. sp., Terranovella brevis n. sp., Simulolenus quadrisulcatus n. gen., n. sp., Dicanthopyge convergens n. gen., n. sp., Dicanthopyge quadrata n. sp., Dicanthopyge reductus n. sp. Aphelaspis longispina n. sp. Olenaspella paucisegmenta n. sp., Litocephalus magnus n. sp., Stenambon megagranulus _n. gen., n. sp. Stenambon paucigranulus n. sp., Parahousia .~Jllbequalis n. sp., Prehousia diverta n. sp., Prehousia impolita n. sp., Preltousia indenta n. sp., Prehousia pr•ima n. sp., Tumicephalus depressus n. gen., n. sp., Oernuolimbus laevifrons n. sp., Oernuolimbus granulosus n. sp., Strigambitus bilobus n. gen., n. sp., Str-igambitus transversus n. sp., Strigambitus? blepharina n. sp., Pterocephalia? punctata n. sp., Erimanium? brachyamis n. sp., Eriman...

The SPICE carbon isotope excursion in Siberia: a combined study of the upper Middle Cambrian–lowermost Ordovician Kulyumbe River section, northwestern Siberian Platform

“…Non-evolutionary changes in trilobite complexes, such as migrations, have been suggested, however, to be common especially at the beginning of the G. reticulatus Biozone (Rozanov et al 1992). Palmer (1965Palmer ( , 1979 also noted that diachronous boundaries of biostratigraphic units occurred in the Middle and Upper Cambrian, but he later suggested that the difference was not significant for biostratigraphic correlation (Palmer, 1984).…”

Exotic trilobites from the uppermost Cambrian Series 3 and lower Furongian of Sweden

“…It has mainly been recorded from North America (Walcott 1924;Kobayashi 1938;Palmer 1954Palmer , 1960Palmer , 1965a; other occurrences include the Gorny Altai Mountains (Romanenko and Romanenko 1967) and northern China (Zhu et al 1979).…”

“…Another trilobite from the Agnostus pisiformis Zone, Olenus alpha Henningsmoen, 1957 of Norway was considered a representative of Simulolenus Palmer, 19654 (Henningsmoen 1957aNikolaisen and Henningsmoen 1985), a genus characteristic of the Steptoean Dunderbergia Zone of the Great Basin, USA (Palmer 1965a). The specimens at hand differ from Simulolenus alpha (Henningsmoen, 1957) in having much larger dimensions, eye-ridges that are more backwardly oblique, and a sagittally much wider anterior border.…”

“…The type species of the genus stated by Jell and Adrain (2003), Conocephalites depressus Shumard, 1861, is not valid as explained earlier by Palmer (1953). REMARKS: Palmer (1953Palmer ( , 1954Palmer ( , 1960Palmer ( , 1962Palmer ( , 1965a discussed the concept of the genus, provided emended diagnoses, and described the Laurentian species. Shergold and Cooper (1985), Shergold and Webers (1992) and Cooper et al (1996) described species from the Furongian of Antarctica.…”

“…The specimen is closest to A. subdita Palmer, 1962 from the Steptoean Aphelaspis Zone in Nevada, USA (Palmer 1962(Palmer , 1965a (Ivshin 1955(Ivshin , 1956. Species assigned to Olentella are listed in Shergold et al (1976Shergold et al ( , 2000 and Romanenko (1988).…”