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Left behind – delayed extinction and a relict trilobite fauna in the Cambrian–Ordovician boundary succession (east Laurentian platform, New York)

Published online by Cambridge University Press:  19 November 2010

ED LANDING ,
STEPHEN R. WESTROP ,
BJÖRN KRÖGER  and
ADAM M. ENGLISH
ED LANDING*
Affiliation:
New York State Museum, 222 Madison Avenue, Albany, New York 12230, USA
STEPHEN R. WESTROP
Affiliation:
Oklahoma Museum of Natural History and School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma 73072, USA
BJÖRN KRÖGER
Affiliation:
Museum für Naturkunde, Humboldt Universität zu Berlin, Invalidenstrasse 43, D-10115 Berlin, Germany
ADAM M. ENGLISH
Affiliation:
Chevron Gulf of Mexico Business Unit, 5750 Johnston St., Lafayette, Louisiana 70503, USA
*
†Author for correspondence: [email protected]
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Abstract

Two completely dissimilar faunal changes occur between the Sunwaptan and Skullrockian Stages (Ptychaspid and Symphysurid ‘Biomeres’) in the uppermost Cambrian on the east Laurentian craton. An undolomitized section in the Little Falls Formation in Washington County, New York, shows a typical ‘biomere’ extinction, with highest Sunwaptan trilobites followed by the abrupt appearance of Cordylodus proavus Zone conodonts and the lowest post-extinction trilobites (Parakoldinioidia Endo) 5.0 m higher. This stage boundary interval is very condensed by comparison with coeval Great Basin and Texas sections. Approximately 70 km southwest, typical pre-extinction taxa (the catillicephalid Acheilops Ulrich and several dikelocephalid species) are shown for the first time to persist well beyond the extinction as they occur with middle C. proavus Zone conodonts (Clavohamulus elongatus or, more likely, Hirsutodontus simplex Subzone). The Ritchie Limestone member of the uppermost Little Falls Formation yields a succession of conodont faunas that spans the C. elongatus–H. simplex–Clavohamulus hintzei Subzones (middle–upper C. proavus Zone). These data prove that the trilobites are a relict fauna that persisted into the Symphysurina Zone of the Skullrockian Stage. The massive (burrow-churned), mollusc-dominated Ritchie Limestone, with the second Upper Cambrian cephalopod locality in east Laurentia, represents an inner-shelf refugium for Sunwaptan trilobites that has not been previously encountered. Final extinction of typical Sunwaptan clades is at least locally diachronous, and a simple, genus-based approach to trilobite biostratigraphy in the Cambrian–Ordovician boundary interval is untenable. The relict fauna appears to be distinct at the species level, so it is likely that a viable, species-based biostratigraphy can be developed. Teridontus gallicus Serpagli et al. 2008 is a synonym of T. nakamurai (Nogami, 1967), and T.? francisi Landing sp. nov., with a large base and tiny cusp, is a lower C. proavus Zone form. New trilobites are Acheilops olbermanni Westrop sp. nov. and Parakoldinioidia maddowae Westrop sp. nov. The lowest Ordovician ‘Gailor Dolomite’ is a junior synonym of the Tribes Hill Formation, and the Ritchie Limestone is assigned to the top of the terminal Cambrian Little Falls Formation.

Keywords

Upper CambrianLower OrdovicianNorth AmericaNew Yorkconodontstrilobitesextinction
Type
Original Article
Information
Geological Magazine , Volume 148 , Issue 4 , July 2011 , pp. 529 - 557
Copyright
Copyright © Cambridge University Press 2010

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References

Adrain, J. M. & Westrop, S. R. 2004. A Late Cambrian (Sunwaptan) silicified trilobite fauna from Nevada. Bulletins of American Paleontology 365, 1–56.Google Scholar
Adrain, J. M. & Westrop, S. R. 2006. New earliest Ordovician trilobite genus Milardicurus: the oldest known hystricurid. Journal of Paleontology 80, 650–71.CrossRefGoogle Scholar
Bradley, J. H. 1925. Trilobites of the Beekmantown in the Phillipsburg region of Quebec. Canadian Field Naturalist 39, 5–9.CrossRefGoogle Scholar
Bridge, J. 1931. Geology of the Eminence and Cardareva quadrangles. Missouri Bureau of Geology and Mines, 2nd Series 24, 1–228.Google Scholar
Brook, B. W., Sodhi, N. S. & Bradshaw, C. A. J. 2008. Synergies among extinction drivers under global change. Trends in Ecology and Evolution 23, 453–60.CrossRefGoogle ScholarPubMed
Chen, J.-Y. & Gong, W.-L. 1986. Conodonts. In Aspects of Cambrian–Ordovician Boundary in Dayangcha, China (ed. Chen, J.-Y.), pp. 93–223. Beijing: China Prospect Publishing House.Google Scholar
Chen, J.-Y. & Teichert, C. 1983. Cambrian Cephalopoda of China. Palaeontographica Abteilung A 181, 1–102.Google Scholar
Chen, J.-Y., Tsou, S.-P., Chen, T.-E. & Qi, D.-L. 1979. Late Cambrian cephalopods of North China. Plectronocerida, Proactinocerida (ord. nov.) and Yanhecerida (ord. nov.) Acta Palaeontologica Sinica 18, 1–24.Google Scholar
Choi, D. K., Kim, D. H., Sohn, J. W, & Lee, S-B. 2003. Trilobite faunal successions across the Cambrian-Ordovician boundary intervals in Korea and their correlation with China and Australia. Journal of Asian Earth Sciences 21, 781–93.CrossRefGoogle Scholar
Clark, T. H. 1948. Theodenisia, new name, replacing Denisia Clark. Journal of Paleontology 22, 643.Google Scholar
Cuvier, G. 1797. Tableau élémentaire de l'historie naturelle des animaux. Publisher or printer not recorded, Paris, 710 pp.CrossRefGoogle Scholar
Dean, W. T. 1977. The early Ordovician trilobite genus Missisquoia Shaw, 1951, in the southern Canadian Rockies of Alberta and British Columbia. Geological Survey of Canada Paper 76–33, 1–7.Google Scholar
Dean, W. T. 1989. Trilobites of the Survey Peak, Outram and Skoki Formations (Upper Cambrian–Lower Ordovician) at Wilcox Pass, Jasper National Park. Alberta. Geological Survey of Canada Bulletin 389, 1–141.Google Scholar
Didham, R. K., Tylianikis, J. M., Gemmell, N. J., Rand, T. A. & Ewers, R. M. 2007. Interactive effects of habitat modification and species invasion on native species decline. Trends in Ecology and Evolution 22, 489–96.CrossRefGoogle ScholarPubMed
Druce, E. C. & Jones, P. J. 1971. Cambro-Ordovician conodonts from the Burke River structural belt, Queensland. Bureau of Mineral Resources, Geology and Geophysics, Canberra, A. C. T. Bulletin 110, 1–159.Google Scholar
Drygant, D. M. 1974. Prostyle konodonty Silura I nizov Devona Volyno-Podolya. Paleontologishe Siborny Lvov Universitaet 10, 64–70.Google Scholar
Eichenberg, W. 1930. Conodonten aus dem Culm des Harzes. Paläontologisches Zeitschrift 12, 177–82.CrossRefGoogle Scholar
Endo, R. 1937. Addenda to Parts 1 and 2. Manchurian Science Museum Bulletin 1, 302–69, 435–61.Google Scholar
Epstein, A. G., Epstein, J. B. & Harris, L. D. 1977. Conodont color alteration—an index to organic metamorphism. United States Geological Survey Professional Paper 995, 1–27.Google Scholar
Erdtmann, B.-D. 1986. Early Ordovician eustatic cycles and their bearing on punctuations in early nematophorid (planktic) graptolite evolution. Lectures in Earth Sciences 8, 139–52.CrossRefGoogle Scholar
Ergaliev, G. K. 1980. Middle and Upper Cambrian trilobites from Maly Karatau. Kazakhstan SSR Academy of Sciences, 211 pp. [in Russian]Google Scholar
Ethington, R. L. & Clark, D. L. 1971. Lower Ordovician conodonts in North America. In Symposium on Conodont Biostratigraphy (eds Sweet, W. C. and Bergström, S. M.), pp. 63–82. Geological Society of America Memoir no. 127.Google Scholar
Fåhraeus, L. E. & Roy, K. 1993. Conodonts from the Cambro-Ordovician Cooks Brook and Middle Arm Formations, Bay of Islands, western Newfoundland. Geologica et Palaeontologica 27, 1–35.Google Scholar
Fisher, D. W. 1954. Lower Ordovician (Canadian) stratigraphy of the Mohawk valley. Bulletin of the Geological Society of America 65, 71–96.CrossRefGoogle Scholar
Fisher, D. W. 1977. Correlation of Hadrynian, Cambrian, and Ordovician rocks in New York State. New York State Museum Map and Chart Series 25, 1–75.Google Scholar
Fisher, D. W. 1984. Bedrock geology of the Glens Falls–Whitehall region, New York. New York State Museum, Map and Chart Series 35, 1–65.Google Scholar
Fisher, D. W. & Hanson, G. F. 1951. Revisions in the geology of Saratoga Springs, New York, and vicinity. American Journal of Science 249, 795–814.CrossRefGoogle Scholar
Fisher, D. W. & Mazzullo, S. J. 1976. Lower Ordovician (Gasconadian) Great Meadows Formation in eastern New York. Geological Society of America Bulletin 87, 1443–8.2.0.CO;2>CrossRefGoogle Scholar
Flower, R. H. 1954. Cambrian cephalopods. New Mexico Institute of Mining and Technology Bulletin 40, 1–51.Google Scholar
Flower, R. H. 1964. The nautiloid order Ellesmeroceratida (Cephalopoda). New Mexico Institute of Mining and Technology Memoir 12, 1–164.Google Scholar
Friedman, G. M. 1980. Dolomite is an evaporate mineral: evidence from the rock record and from sea-marginal ponds of the Red Sea. In Concepts and Models of Dolomitization (eds Zenger, D. H., Dunham, J. B. & Ethington, R. L.), pp. 69–80. SEPM Special Publication no. 28.CrossRefGoogle Scholar
Fortey, R. A. 1983. Cambrian–Ordovician trilobites from the boundary beds in western Newfoundland and their phylogenetic significance. Special Papers in Palaeontology 30, 179–211.Google Scholar
Fortey, R. A., Landing, E., & Skevington, D. 1982. Cambrian-Ordovician boundary sections in the Cow Head Group, western Newfoundland. In The Cambrian–Ordovician boundary: sections, fossil distributions and correlations (eds Bassett, M. G. & Dean, W. T.), pp. 95–129. National Museum of Wales, Geological Series 3.Google Scholar
Furnish, W. M. 1938. Conodonts from the Prairie du Chien (Lower Ordovician) beds of the upper Mississippi valley. Journal of Paleontology 12, 318–40.Google Scholar
Geyer, G. & Shergold, J. H. 2000. The quest for internationally recognized divisions of Cambrian time. Episodes 23, 188–95.CrossRefGoogle Scholar
Hall, J. 1863. Preliminary notice of the fauna of the Potsdam sandstone, with remarks on previously known species of fossils and descriptions of some new ones from the sandstones of the Upper Mississippi Valley. Report of the New York State Cabinet of Natural History 16, 119–222.Google Scholar
Hanski, I., Koivulehto, H., Cameron, A., & Rahagalala, P. 2007. Deforestation and apparent extinctions of endemic forest beetles in Madagascar. Biology Letters 3, 344–7.CrossRefGoogle ScholarPubMed
Haq, B. U. & Schutter, S. R. 2008. A chronology of Paleozoic sea-level changes. Science 322, 64–8.CrossRefGoogle ScholarPubMed
Harris, G. & Pimm, S. L. 2008. Range size and extinction risk in birds. Conservation Biology 22, 163–71.CrossRefGoogle Scholar
Hupé, P. 1955. Classification des trilobites. Annales de Paléontologie 41, 91–325.Google Scholar
Jablonski, D. 1986. Causes and consequences of mass extinction: a comparative approach. In Dynamics of Extinction (ed. Elliot, D.K.), pp. 183–229. New York: Wiley & Sons.Google Scholar
Ji, Z. & Barnes, C. R. 1994. Lower Ordovician conodonts of the St. George Group, Port au Port Peninsula, western Newfoundland, Canada. Palaeontographica Canadiana 11, 1–149.Google Scholar
Kaljo, D., Borovko, N., Heinsalu, H., Khasanovich, K., Mens, K., Popov, L., Sergeeva, S., Sobolevskaya, R. & Viira, V. 1986. The Cambrian–Ordovician boundary in the Baltic Lagoda Clint area (north Estonia and Leningrad region), USSR). Proceedings of the Academy of Sciences of the Estonian SSR, Geology 35, 97–108.Google Scholar
Kobayashi, T. 1955. The Ordovician fossils of the McKay Group in British Columbia, western Canada, with a note on the Early Ordovician palaeogeography. Journal of the Faculty of Science, University of Tokyo, Section 2 – Geology 9, 355–493.Google Scholar
Kröger, B. & Landing, E. 2007. The earliest Ordovician cephalopods of eastern Laurentia—ellesmeroceroids of the Tribes Hill Formation, eastern New York. Journal of Paleontology 81, 841–56.CrossRefGoogle Scholar
Kröger, B. & Landing, E. 2008. Onset of the Ordovician cephalopod radiation – evidence from the Rochdale Formation (middle Early Ordovician, Stairsian) in eastern New York. Geological Magazine 145, 490–520.CrossRefGoogle Scholar
Kröger, B. & Landing, E. 2009. Cephalopods and paleoenvironments of the Fort Cassin Formation (upper Lower Ordovician), eastern New York and adjacent Vermont. Journal of Paleontology 83, 664–93.CrossRefGoogle Scholar
Landing, E. 1979. Conodonts and biostratigraphy of the Hoyt Limestone (Late Cambrian, Trempealeauan), eastern New York. Journal of Paleontology 53, 1023–29.Google Scholar
Landing, E. 1988. Cambrian–Ordovician boundary in North America: revised Tremadocian correlations, unconformities, and “glacioeustasy”. In The Canadian Paleontology and Biostratigraphy Seminar, Proceedings (ed. Landing, E.), pp. 48–58. New York State Museum Bulletin 462.Google Scholar
Landing, E. 1993. Cambrian–Ordovician boundary in the Taconic allochthon, eastern New York, and its interregional correlation. Journal of Paleontology 67, 1–19.CrossRefGoogle Scholar
Landing, E. 2002. Early Paleozoic sea levels and climates: new evidence from the east Laurentian shelf and slope. In Guidebook for Fieldtrips in New York and Vermont (eds McLelland, J. & Karabinos, P.), pp. C6–1–C6–22. New England Intercollegiate Geological Conference 94th Annual Meeting and New York State Geological Association 74th Annual Meeting, Lake George, NY.Google Scholar
Landing, E. 2007. Ediacaran–Ordovician of east Laurentia―geologic setting and controls on deposition along the New York Promontory. In Ediacaran–Ordovician of East Laurentia―S. W. Ford Memorial Volume (ed. Landing, E.), pp. 5–24. New York State Museum Bulletin 510.Google Scholar
Landing, E. In press. The lives and deaths of the Great American Carbonate Bank in eastern Laurentia. In The Great American Carbonate Bank: The Geology and Petroleum Potential of the Cambrian–Ordovician Sauk Sequence of Laurentia (eds Derby, J., Fritz, R., Morgan, W. A., Sternbach, C., Kupecz, J., Kuykendall, M., Longacre, S. A., & Medlock, P.). American Association of Petroleum Geologists Memoir.Google Scholar
Landing, E., Bowring, S. A., Davidek, K., Westrop, S. R., Geyer, G. & Heldmaier, W. 1998. Duration of the Early Cambrian: U-Pb ages of volcanic ashes from Avalon and Gondwana. Canadian Journal of Earth Sciences 35, 329–38.CrossRefGoogle Scholar
Landing, E., Franzi, D. A., Hagadorn, J. W., Westrop, S. R., Kröger, B. & Dawson, J. 2007. Cambrian of east Laurentia: field workshop in eastern New York and western Vermont. In Ediacaran–Ordovician of East Laurentia―S. W. Ford Memorial Volume (ed. Landing, E.), pp. 25–80. New York State Museum Bulletin 510.Google Scholar
Landing, E. & Kröger, B. 2009. The oldest cephalopods from east Laurentia. Journal of Paleontology 83, 89–93.CrossRefGoogle Scholar
Landing, E., Ludvigsen, R & von Bitter, P. H. 1980. Upper Cambrian to Lower Ordovician conodont biostratigraphy and biofacies, Rabbitkettle Formation, District of Mackenzie. Royal Ontario Museum, Life Sciences Contributions 126, 1–42.Google Scholar
Landing, E. & Murphy, J. B. 1991. Uppermost Precambrian(?)–Lower Cambrian of mainland Nova Scotia: faunas, depositional environment, and stratigraphic revision. Journal of Paleontology 65, 382–96.CrossRefGoogle Scholar
Landing, E. & Westrop, S. R. 2006. Early Ordovician faunas, stratigraphy, and sea-level history of the middle Beekmantown Group, northeastern New York. Journal of Paleontology 80, 958–80.CrossRefGoogle Scholar
Landing, E., Westrop, S. R. & Keppie, J. D. 2007. Terminal Cambrian and lowest Ordovician succession of Mexican West Gondwana: biotas and sequence stratigraphy of the Tiñu Formation. Geological Magazine 144, 1–28.CrossRefGoogle Scholar
Landing, E., Westrop, S. R. & Knox, L. 1996. Conodonts, stratigraphy, and relative sea-level changes of the Tribes Hill Formation (Lower Ordovician), east-central New York. Journal of Paleontology 70, 652–76.CrossRefGoogle Scholar
Landing, E., Westrop, S. R. & Miller, J. F. 2010. Globally practical base for the uppermost Cambrian (Stage 10)—FAD of the conodont Eoconodontus notchpeakensis and the Housian Stage. In The 15th Field Conference of the Cambrian Stage Subdivision Working Group, International Commission on Cambrian Stratigraphy. Abstracts and Excursion Guide. (eds Fatka, O. & Budil, P.), p. 18. Prague: Czech Geological Survey.Google Scholar
Landing, E., Westrop, S. R. & Van Aller Hernick, L. 2003. Uppermost Cambrian–Lower Ordovician faunas and Laurentian platform sequence stratigraphy, eastern New York and Vermont. Journal of Paleontology 77, 78–98.Google Scholar
Lee, S-B., Lee, D-C. & Choi, D. K. 2008. Cambrian–Ordovician family Missisquoiidae Hupé, 1955: systematic revision and palaeogeographical considerations based upon cladistic analysis. Palaeogeography, Palaeoclimatology, Palaeoecology 260, 315–41.CrossRefGoogle Scholar
Loch, J. D., Stitt, J. H. & Derby, J. R. 1993. Cambrian–Ordovician boundary interval extinctions: implications of revised trilobite and brachiopod data from Mount Wilson, Alberta, Canada. Journal of Paleontology 67, 497–517.CrossRefGoogle Scholar
Lochman-Balk, C. 1970. Upper Cambrian faunal patterns on the craton. Geological Society of America Bulletin 81, 3197–224.CrossRefGoogle Scholar
Longacre, S. A. 1970. Trilobites of the Upper Cambrian Ptychaspid Biomere, Wilberns Formation, central Texas. Paleontological Society Memoir 4, 1–70.Google Scholar
Ludvigsen, R. 1982. Upper Cambrian and Lower Ordovician trilobite biostratigraphy of the Rabbitkettle Formation, western District of Mackenzie. Life Sciences Contribution, Royal Ontario Museum 134, 1–188.Google Scholar
Ludvigsen, R. & Westrop, S. R. 1983 a. Franconian trilobites of New York State. New York State Museum Memoir 23, 1–83.Google Scholar
Ludvigsen, R. & Westrop, S. R. 1983 b. Trilobite biofacies of the Cambrian–Ordovician boundary interval in northern North America. Alcheringa 7, 301–19.CrossRefGoogle Scholar
Ludvigsen, R. & Westrop, S. R. 1985. Three new Upper Cambrian stages for North America. Geology 13, 139–43.2.0.CO;2>CrossRefGoogle Scholar
Ludvigsen, R., Westrop, S. R. & Kindle, C. H. 1989. Sunwaptan (Upper Cambrian) trilobites of the Cow Head Group, western Newfoundland, Canada. Palaeontographica Canadiana 6, 1–175.Google Scholar
Mazzulo, S. J., Agostino, P., Seitz, N. & Fisher, D. W. 1978. Stratigraphy and depositional environment of the Upper Cambrian–Lower Ordovician sequence, Saratoga Springs, New York. Journal of Sedimentary Petrology 48, 99–116.Google Scholar
Miller, J. F. 1969. Conodont faunas and biostratigraphy of the Upper Cambrian and lowest Ordovician, House Range, Utah. Journal of Paleontology 43, 413–39.Google Scholar
Miller, J. F. 1980. Taxonomic revisions of some Upper Cambrian and lowest Ordovician conodonts with comments on their evolution. University of Kansas Paleontological Institute Paper 99, 1–39.Google Scholar
Miller, J. F. 1984. Cambrian and earliest Ordovician conodont evolution, biofacies and provincialism. In Conodont biofacies and provincialism (ed. Clark, D. L.), pp. 43–68. Geological Society of America Special Paper 196.CrossRefGoogle Scholar
Miller, J. F., Evans, K. R., Loch, J. D., Ethington, R. L., Stitt, J. H., Holmer, L. & Popov, L. E. 2003. Stratigraphy of the Sauk III interval (Cambrian–Ordovician) in the Ibex area, western Millard County, Utah, and central Texas. Brigham Young University Geology Studies 47, 23–118.Google Scholar
Miller, S. A. 1899. North American Geology and Palaeontology for the Use of Amateurs, Students and Scientists. Publisher not listed, Cincinnati, Ohio, 718 pp.Google Scholar
Missarzhevsky, V. V. 1969. Opisanie chioitov, gastropod, chiolitchelminthov, kamenid i form nizsnego sistematneskogo poloshenia. In Tommotski Yarus I Problemii Nizhneii Yaranish Kembriya (ed. Raaben, A.) Trudy Leona Nict. AH CCCP, 206, pp. 93–175.Google Scholar
Müller, K. J. 1959. Kambrische Conodonten. Zeitschrift für Deutsche Geologische Gesellschaften 111, 434–85.CrossRefGoogle Scholar
Müller, K. J. 1964. Conodonten aus dem Unteren Ordovicium von Sudkorea. Neues Jahrbuch der Geologie und Paläontologie, Abhandlungen 119, 93–102.Google Scholar
Müller, K. J., Nogami, Y. & Lenz, H. 1974. Phosphatische Ringe als Mikrofossilien in Altpaläozoikum. Palaeontographica Abteilung A 146, 79–99.Google Scholar
Nicoll, R. S. 1994. Seximembrate apparatus of the Late Cambrian coniform conodont Teridontus nakamurai from the Chatsworth Limestone, Georgina Basin, Queensland. AGSO Journal of Australian Geology & Geophysics 15, 367–79.Google Scholar
Nielsen, A. T. 2004. Ordovician sea level changes: a Baltoscandian perspective. In The Great Ordovician Biodiversification Event (eds Webby, B. D., Paris, F., Droser, M. L. & Percival, I. G.), pp. 84–93. New York: Columbia University Press.CrossRefGoogle Scholar
Nogami, Y. 1967. Kambrische Conodonten von China, Teil 2, Conodonten aus den hoch obercambrischen Yencho-Schichten. Kyoto University College of Sciences, Memoir Series B 33, 211–19.Google Scholar
Palmer, A. R. 1965. Biomere, a new kind of biostratigraphic unit. Journal of Paleontology 39, 149–53.Google Scholar
Palmer, A. R. 1998. A proposed nomenclature for stages and series for the Cambrian of Laurentia. Canadian Journal of Earth Sciences 35, 323–8.CrossRefGoogle Scholar
Pander, C. H. 1856. Monographie der fossilen Fische des silurischen Systems der Russisch-Baltischen Gouvernments. Akademie der Wissenschaft, St. Petersburg, 91 pp.Google Scholar
Peng, S. 1992. Upper Cambrian biostratigraphy and trilobite faunas of the Cili-Taoyuan area, northwestern Hunan, China. Association of Australasian Palaeontologists Memoir 13, 1–119.Google Scholar
Pimm, S. L. & Askins, R. A. 1995. Forest losses predict bird extinctions in eastern North America. Proceedings of the National Academy of Sciences, USA 92, 9343–7.CrossRefGoogle ScholarPubMed
Rasetti, F. 1959. Trempealeauian trilobites from the Conococheague, Frederick, and Grove Limestones of the central Appalachians. Journal of Paleontology 33, 575–98.Google Scholar
Raymond, p. E. 1913. Notes on some new and old trilobites in the Victoria Memorial Museum, Canada Geological Survey. Bulletin of the Victoria Memorial Museum 1, 33–9.Google Scholar
Raymond, P. E. 1937. Upper Cambrian and Lower Ordovician Trilobita and Ostracoda from Vermont. Geological Society of America Bulletin 48, 1079–146.CrossRefGoogle Scholar
Robison, R. A. & Pantoja-Alor, J. 1968. Tremadocian trilobites from the Nochixtlán region, Oaxaca, Mexico. Journal of Paleontology 42, 767–800.Google Scholar
Rowley, E. B. 1951. Crystal collecting at Saratoga Springs, N.Y. Rocks and Minerals September–October 1951, 528–32.Google Scholar
Schulte, P. E, Alegret, L., Arenillas, I., Arz, J. A.Barton, P. J., Bown, P. R., Bralower, T. J., Christeson, G. L., Claeys, P., Cockell, C. S., Collins, G. S., Deutsch, Al., Goldin, T. J., Goto, K., Grajales-Nishimura, J. M., Grieve, R. A. F., Gulick, S. P. S., Johnson, K. R., Kiessling, W., Koeberl, C., Kring, D. A., Macleod, K. G., Matsui, T., Melosh, J., Montanari, A., Morgan, J. V., Neal, C. R., Nichols, D. J., Norris, R. D., Pierazzo, E., Ravizza, G., Rebolledo-Vieyra, M., Reimold, W. U., Robin, E., Salge, T., Speijer, R. P., Sweet, A. R., Urrutia-Fucugauchi, J., Vajda, V., Whalen, M. T. & Willumsen, P. S. 2010. The Chicxulub asteroid impact crater and mass extinction at the Cretaceous–Paleogene boundary. Science 327, 1214–18.CrossRefGoogle Scholar
Scotese, C. R. & McKerrow, W. S. 1990. Revised world maps and introduction. Geological Society of London Memoir 12, 1–21.CrossRefGoogle Scholar
Serpagli, E., Ferretti, A., Nicoll, R. S. & Serventi, P. 2008. The conodont genus Teridontus (Miller, 1980) [sic., delete parentheses] from the Early Ordovician from the Montagne Noire, France. Journal of Paleontology 82, 612–20.CrossRefGoogle Scholar
Shaw, A. B. 1951. The paleontology of northwestern Vermont. I. New Late Cambrian trilobites. Journal of Paleontology 25, 97–114.Google Scholar
Shergold, J. H. 1971. Late Upper Cambrian trilobites from the Gola Beds, western Queensland. Australian Bureau of Mineral Resources, Geology and Geophysics Bulletin 112, 1–127.Google Scholar
Shergold, J. H. 1975. Late Cambrian and Early Ordovician trilobites from the Burke River Structural Belt, western Queensland, Australia. Australian Bureau of Mineral Resources, Geology and Geophysics Bulletin 153, 1–251.Google Scholar
Sohn, J. W. & Choi, D. K. 2007. Furongian trilobites from the Asioptychaspis and Quadraticephalus Zones of the Hwajeol Formation, Taebaeksan Basin, Korea. Geosciences Journal 11, 297–314.CrossRefGoogle Scholar
Stitt, J. H. 1971 a. Repeating evolutionary patterns in Late Cambrian biomeres. Journal of Paleontology 45, 178–81.Google Scholar
Stitt, J. H. 1971 b. Late Cambrian and earliest Ordovician trilobites, Timbered Hills and lower Arbuckle Groups, western Arbuckle Mountains, Murray County, Oklahoma. Oklahoma Geologic Survey Bulletin 110, 1–83.Google Scholar
Stitt, J. H. 1975. Adaptive radiation, trilobite paleoecology and extinction, Ptychaspid Biomere, Late Cambrian of Oklahoma. Fossils and Strata 4, 381–90.CrossRefGoogle Scholar
Stitt, J. H. 1977. Late Cambrian and earliest Ordovician trilobites, Wichita Mountains area, Oklahoma. Oklahoma Geological Survey Bulletin 124, 1–79.Google Scholar
Szaniawski, H. & Bengtson, S. 1998. Late Cambrian euconodonts from Sweden. Palaeontologica Polonica 58, 7–29.Google Scholar
Taylor, M. E. & Halley, R. B. 1974. Systematics, environment, and biogeography of some Late and Early Ordovician trilobites from eastern New York State. U. S. Geological Survey Professional Paper 834, 1–38.Google Scholar
Ulrich, E. O. & Cushing, H. P. 1910. Age and relations of the Little Falls Dolomite (Calciferous) of the Mohawk valley. New York State Museum Bulletin 140, 97–140.Google Scholar
Ulrich, E. O. & Resser, C. E. 1930. The Cambrian of the upper Mississippi Valley. Part 1. Trilobita; Dikelocephalinae and Osceolinae. Bulletin of the Milwaukee Public Museum 12, 1–122.Google Scholar
Ulrich, E. O. & Resser, C. E. 1933. The Cambrian of the Upper Mississippi Valley. Part 2. Trilobita; Saukiinae. Bulletin of the Milwaukee Public Museum 12, 123–306.Google Scholar
Walch, J. E. I. 1771. Die Naturgeschichte der Versteinerungen zur Erläuterung der Knorrischen Sammlung von Merkwürdigkeiten der Natur. Dritter Theil. Paul Jonathan Felstecker, Nürnburg, 235 pp.Google Scholar
Walcott, C. D. 1912. New York Potsdam–Hoyt fauna. Smithsonian Museum Miscellaneous Collections 57, 251–304.Google Scholar
Walcott, C. D. 1914. Dikelocephalus and other genera of the Dikelocephalinae. Smithsonian Miscellaneous Collections 57, 345–413.Google Scholar
Westrop, S. R. 1986 a. New ptychaspidid trilobites from the Upper Cambrian Mistaya Formation of southern Alberta. Canadian Journal of Earth Sciences 23, 214–21.CrossRefGoogle Scholar
Westrop, S. R. 1986 b. Trilobites of the Upper Cambrian Sunwaptan Stage, southern Canadian Rocky Mountains, Alberta. Palaeontographica Canadiana 3, 1–179.Google Scholar
Westrop, S. R. 1995. Sunwaptan and Ibexian (Upper Cambrian and Lower Ordovician) trilobites of the Rabbitkettle Formation, Mountain River region, northern Mackenzie Mountains, northwest Canada. Palaeontographica Canadiana 12, 1–75.Google Scholar
Westrop, S. R. & Cuggy, M. B. 1999. Comparative paleoecology of Cambrian trilobite extinctions. Journal of Paleontology 73, 337–54.CrossRefGoogle Scholar
Westrop, S. R., Knox, L. A. & Landing, E. 1993. Lower Ordovician (Ibexian) trilobites from the Tribes Hill Formation, central Mohawk valley, New York State. Canadian Journal of Earth Sciences 30, 1618–33.CrossRefGoogle Scholar
Westrop, S. R. & Ludvigsen, R. 1987. Biogeographic control of trilobite mass extinction at an Upper Cambrian ‘biomere’ boundary. Paleobiology 13, 84–99.CrossRefGoogle Scholar
Westrop, S. R., Palmer, A. R. & Runkel, A. 2005. A new Sunwaptan (Late Cambrian) trilobite fauna from the upper Mississippi Valley. Journal of Paleontology 79, 72–88.2.0.CO;2>CrossRefGoogle Scholar
Winston, D. & Nicholls, H. 1967. Late Cambrian and Early Ordovician faunas from the Wilberns Formation of central Texas. Journal of Paleontology 41, 66–96.Google Scholar
Zenger, D. H. 1971. Age and relationships of the Ritchie Limestone, New York. Geological Society of America Abstracts with Programs, Northeastern Section, p. 65.Google Scholar
Zhou, Z. & Zhang, J. 1978. Cambrian-Ordovician boundary of the Tangshan area with descriptions of the related trilobite fauna. Acta Palaeontologica Sinica 17, 1–28.Google Scholar