No CrossRef data available.
Article contents
Cladistic analysis of early-Middle Cambrian kochaspid trilobites (Ptychopariida)
Published online by Cambridge University Press: 20 May 2016
Abstract
Cambrian ptychopariids have defied most attempts at higher classification. Even at the generic level, there is no consensus as to what constitutes identification criteria in these morphologically conservative trilobites. The problem is more acute when there is a lack of knowledge about the different sclerites of species, the presence of species with morphologies intermediate between two genera, the naming of genera where incompletely known or poor quality specimens were used for type species, and the use of character checklists to generate diagnoses for higher taxa. This study on the kochaspid trilobites (Lower to Middle Cambrian) uses several available representatives of each genus to alleviate or assess some of these problems. Successive reweighting of characters is used for the assessment of 70 characters among 66 taxa as to their importance in forming clades. Results of this study include five important points about ptychopariid classification: 1) knowledge about noncranidial sclerites is important for the proper placement of taxa that have generalized morphologies; 2) in contrast, taxa that have more derived cranidial morphology can be accurately placed within a clade; 3) intermediate morphologies illustrate a close link between genera, but these forms can present nomenclatural problems in their placement; 4) although genera defined by type species based on incompletely described or poorly preserved specimens can create nomenclatural nightmares, other species assigned to these genera are not dependent on their previous taxonomic assignment for their placement in the cladogram; and 5) checklists of morphological characters cannot be used to recognize ptychopariid groups, since the level of homoplasy is too high and there are too many reversals of character states within a clade. Instead, a list of character states that typify a taxonomic group is more useful and will lead to a more stable classification.
This cladistic analysis of kochaspid trilobites indicates that 64 of the 70 characters were useful in the formation of clades. Fifty-six cranidial, librigenal, thoracic, and pygidial characters were useful in typifying larger and smaller clades. The analysis also indicates that Eokochaspis, Nyella, and Onchocephalus are polyphyletic. Reassignments based on the cladistic analysis include Schistometopus collaris to Caborcella, and Syspacephalus obscurus to Mexicella.
- Type
- Research Article
- Information
- Copyright
- Copyright © The Paleontological Society
References
Ahlberg, P., and Bergström, J. 1978. Lower Cambrian ptychopariid trilobites from Scandinavia. Sverges Geologiska Undersökning, 49, 41 p.Google Scholar
Babcock, L. E. 1994. Systematics and phylogenetics of polymeroid trilobites from the Henson Gletscher and Kap Stanton formations (Middle Cambrian), North Greenland. Bulletin Gr⊘nlands Geologiske Undersoegelse, 169:79–127.Google Scholar
Blaker, M. R., and Peel, J. S. 1997. Lower Cambrian trilobites from North Greenland. Meddelelser on Gr⊘nland, Geoscience, 35, 145 p.Google Scholar
Chang, Wentang, and Jell, P. A. 1987. Cambrian Trilobites of North China. Science Press, Beijing, China, 459 p.Google Scholar
Chappill, J. A. 1989. Quantitative characters in phylogenetic analysis. Cladistics, 5:217–234.Google Scholar
Cotton, T. J. 2001. The phylogeny and systematics of blind Cambrian ptychoparioid trilobites. Palaeontology, 44:167–207.Google Scholar
Eddy, J. D., and McCollum, L. B. 1998. Early Middle Cambrian Albertella Biozone trilobites of the Pioche Shale, southeastern Nevada. Journal of Paleontology, 72:864–887.Google Scholar
Edgecombe, G. D. 1992. Trilobite phylogeny and the Cambrian-Ordovician “event”: cladistics reappraisal, p. 144–177. In Novacek, M. J. and Wheeler, Q. D. (eds.), Extinction and Phylogeny. Columbia University Press, New York.Google Scholar
Fortey, R. A. 1990. Ontogeny, hypostome attachment and trilobite classification. Palaeontology, 33:529–576.Google Scholar
Fortey, R. A. 1997. Phylogenetic concepts in the history of trilobite classifications. Second International Trilobite Conference, Brock University, St. Catharines, Ontario. Abstracts with Program, p. 22–23.Google Scholar
Fortey, R. A. 2001. Trilobite systematics: the last 75 years. Journal of Paleontology, 75:1141–1151.Google Scholar
Fortey, R. A., and Chatterton, B. D. E. 1988. Classification of the trilobite suborder Asaphina. Palaeontology, 31:165–222.Google Scholar
Fritz, W. H. 1968. Lower and early Middle Cambrian trilobites from the Pioche Shale, east-central Nevada, U.S.A. Palaeontology, 11:183–235.Google Scholar
Lieberman, B. S. 1998. Cladistic analysis of the Early Cambrian olenelloid trilobites. Journal of Paleontology, 72:59–78.Google Scholar
Lieberman, B. S. 2001. Phylogenetic analysis of the Olenellina Walcott, 1890 (Trilobita, Cambrian). Journal of Paleontology, 75:96–115.Google Scholar
Lochman, C. 1947. Analysis and revision of eleven Lower Cambrian trilobite genera. Journal of Paleontology, 21:59–71.Google Scholar
Lochman, C. 1948. New Cambrian trilobite genera from northwest Sonora, Mexico. Journal of Paleontology, 22:451–467, pls. 69–70.Google Scholar
Lochman, C. 1952. Trilobites, p. 60–162. In Cooper, G. A., Arellano, A. R. V., Johnson, J. H., Okulitch, V. J., Stayanow, A., and Lochman, C. (eds.), Cambrian Stratigraphy and Paleontology Near Caborca, Northwestern Sonora, Mexico. Smithsonian Miscellaneous Collections, 119 (1), 184 p., 31 pls.Google Scholar
Longacre, S. A. 1970. Trilobites of the Upper Cambrian Ptychaspid biomere, Wilberns Formation, central Texas. Paleontological Society Memoir, 4, 70 p.Google Scholar
Ludvigsen, R., and Westrop, S. R. 1983. Franconian trilobites of New York State. New York State Museum Memoir, 23, 83 p.Google Scholar
Ludvigsen, R., Westrop, S. R., and Kindle, C. H. 1989. Sunwaptan (Upper Cambrian) trilobites of the Cow Head Group, western Newfoundland, Canada. Palaeontographica Canadiana, 6:1–175.Google Scholar
Melzak, A., and Westrop, S. R. 1994. Mid-Cambrian (Marjuman) trilobites from the Pika Formation, southern Canadian Rocky Mountains, Alberta. Canadian Journal of Earth Science, 31:969–985.Google Scholar
Merriam, C. W. 1964. Cambrian Rocks of the Pioche Mining District, Nevada. U. S. Geological Survey Professional Paper, 469, 59 p.Google Scholar
Moore, R. C., (ed.). 1959. Arthropoda 1. Treatise on Invertebrate Paleontology, Pt. O. Geological Society of America and University of Kansas Press, Lawrence, 560 p.Google Scholar
Norford, B. S. 1968. A Middle Cambrian Plagiura-Poliella Faunule from Southwest District of Mackenzie. Geological Survey of Canada Bulletin, 163:29–38, pls. 4–6.Google Scholar
Palmer, A. R. 1954. An appraisal of the Great Basin Middle Cambrian trilobites described before 1900. U.S. Geological Survey Professional Paper, 264-D:53–86.Google Scholar
Palmer, A. R. 1958. Morphology and ontogeny of a Lower Cambrian ptychoparioid trilobite from Nevada. Journal of Paleontology, 32:154–170.Google Scholar
Palmer, A. R. 1965. Trilobites of the Late Cambrian Pterocephaliid biomere in the Great Basin, United States. U.S. Geology Survey Professional Paper, 493, 105 p.Google Scholar
Palmer, A. R., and Halley, R. B. 1979. Physical stratigraphy and trilobite biostratigraphy of the Carrara Formation (Lower and Middle Cambrian) in the southern Great Basin. U.S. Geological Survey Professional Paper, 1047, 131 p.Google Scholar
Poe, S., and Wiens, J. J. 2000. Character selection and the methodology of morphological phylogenetics, p. 20–36. In Wiens, J. J. (ed.), Phylogenetic Analysis of Morphological Data. Smithsonian Series in Comparative Evolutionary Biology, Washington, DC, 220 p.Google Scholar
Poulsen, C. 1927. The Cambrian, Ozarkian and Canadian faunas of northwest greenland. Meddelelser om Gr⊘nland, 70:233–343.Google Scholar
Poulsen, V. 1964. Contribution to the Lower and Middle Cambrian paleontology and stratigraphy of northwest Greenland. Meddelelser om Gr⊘nland, 164(6).Google Scholar
Pratt, B. R. 1992. Trilobites of the Marjuman and Steptoean stages (Upper Cambrian), Rabbitkettle Formation, southern Mackenzie Mountains, northwest Canada. Palaeontolographica Canadiana, 9, 179 p.Google Scholar
Prendini, L. 2001. Species or supraspecific taxa as terminals in cladistic analysis? Groundplans versus exemplars revisited. Systematic Biology, 50:290–300.Google Scholar
Rasetti, F. 1951. Middle Cambrian stratigraphy and faunas of the Canadian Rocky Mountains. Smithsonian Miscellaneous Collections, 116(5), 277 p.Google Scholar
Rasetti, F. 1955. Lower Cambrian ptychopariid trilobites from the conglomerates of Quebec. Smithsonian Miscellaneous Collections, 128(7), 35 p.Google Scholar
Rasetti, F. 1957. Additional fossils from the Middle Cambrian Mt. Whyte Formation of the Canadian Rocky Mountains. Journal of Paleontology, 31:955–972.Google Scholar
Rasetti, F. 1963. Middle Cambrian ptychoparioid trilobites from the conglomerates of Quebec. Journal of Paleontology, 37:575–594, pls. 66–70.Google Scholar
Resser, C. E. 1935. Nomenclature of some Cambrian trilobites. Smithsonian Miscellaneous Collections, 93(5), 29 p.Google Scholar
Resser, C. E. 1936. Second contribution to nomenclature on Cambrian trilobites. Smithsonian Miscellaneous Collections, 95(4), 29 p.Google Scholar
Resser, C. E. 1937. Third contribution to nomenclature on Cambrian trilobites. Smithsonian Miscellaneous Collections, 95(22), 59 p.Google Scholar
Resser, C. E. 1938a. Middle Cambrian fossils from Pend Oreille Lake, Idaho. Smithsonian Miscellaneous Collections, 97(3), 12 p.Google Scholar
Resser, C. E. 1938b. Cambrian system (restricted) of the southern Appalachians. Geological Society America Special Paper, 15, 140 p.Google Scholar
Resser, C. E. 1939a. The Spence Shale and its fauna. Smithsonian Miscellaneous Collections, 97, 29 p., 6 pls.Google Scholar
Resser, C. E. 1939b. The Ptarmigania Strata of the Northern Wasatch Mountains. Smithsonian Miscellaneous Collections, 98, 72 p., 14 pls.Google Scholar
Resser, C. E. 1942. New Upper Cambrian trilobites. Smithsonian Miscellaneous Collections, 103, 136 p., 21 pls.Google Scholar
Robison, R. A. 1988. Trilobites of the Holm Dal Formation (late Middle Cambrian) central North Greenland. Meddelelser om Gr⊘nland Geoscience, 20:23–103.Google Scholar
Sanderson, M. J., and Donaghue, M. J. 1989. Patterns of variation in levels of homoplasy. Evolution, 43:1781–1795.Google Scholar
Schwimmer, D. R. 1975. Quantitative taxonomy and biostratigraphy of Middle Cambrian trilobites from Montana and Wyoming. Mathematical Geology, 7:149–166.CrossRefGoogle Scholar
Stitt, J. H. 1971. Cambrian-Ordovician Trilobites Western Arbuckle Mountains. Oklahoma Geology Survey Bulletin, 110, 83 p.Google Scholar
Stitt, J. H. 1983. Trilobites, biostratigraphy, and lithostratigraphy of the McKenzie Hill Limestone (Lower Ordovician), Wichita and Arbuckle Mountains, Oklahoma. Oklahoma Geology Survey Bulletin, 134, 54 p.Google Scholar
Sundberg, F. A. 1994. Corynexochida and Ptychopariida (Trilobita, Arthropoda) of the Ehmaniella Biozone (Middle Cambrian), Utah and Nevada. Contributions in Science, Los Angeles County Museum of Natural History, 446, 137 p.Google Scholar
Sundberg, F. A. 1999. Redescription of Alokistocare subcoronatum (Hall and Whitfield, 1877), the type species of Alokistocare, and the status of Alokistocaridae, Resser, 1938b (Ptychopariida: Trilobita, Middle Cambrian). Journal of Paleontology, 73:1126–1143.CrossRefGoogle Scholar
Sundberg, F. A., and McCollum, L. B. 1997. Oryctocephalids (Corynexochida: Trilobita) of the Lower-Middle Cambrian boundary interval from California and Nevada. Journal of Paleontology, 71:1065–1090.Google Scholar
Sundberg, F. A., and McCollum, L. B. 2000. Ptychopariid trilobites of the Lower-Middle Cambrian boundary interval, Pioche Shale, southeastern Nevada. Journal of Paleontology, 74:604–630.Google Scholar
Sundberg, F. A., and McCollum, L. B. 2002. Kochiella Poulsen, 1927, and Hadrocephalites new genus (Trilobita: Ptychopariida) from the early Middle Cambrian of western North America. Journal of Paleontology, 76:76–94.Google Scholar
Sundberg, F. A., and McCollum, L. B. 2003a. Trilobites of the lower Middle Cambrian Poliella denticulata Biozone (new) of Southern Nevada. Journal of Paleontology, 77:333–361.Google Scholar
Sundberg, F. A., and McCollum, L. B. 2003b. Early and Mid Cambrian trilobites of the outer shelf deposits of Nevada and California, USA. Palaeontology, 46(5):945–986.Google Scholar
Swofford, D. L. 2003. PAUP∗. Phylogenetic Analysis Using Parsimony (∗ and Other Methods). Version 4. Sinauer Associates, Sunderland, Massachusetts.Google Scholar
Ulrich, E. O. 1929. Paleontology—The status of the classification of trilobites. Journal of the Washington Academy of Sciences, 19:59–63.Google Scholar
Walcott, C. D. 1886. Second contribution to the studies on the Cambrian faunas of North America. U.S. Geological Survey Bulletin, 30:1–369, pls. 1–33.Google Scholar
Walcott, C. D. 1912. Cambrian geology and paleontology 2. No. 8: The Sardinian Cambrian genus Olenopsis in America. Smithsonian Miscellaneous Collections, 57(8):239–249, pl. 36.Google Scholar
Walcott, C. D. 1916. Cambrian geology and paleontology of Cambrian trilobites. Smithsonian Miscellaneous Collections, 64(3):157–258.Google Scholar
Walcott, C. D. 1917a. The Albertella fauna in British Columbia and Montana. Smithsonian Miscellaneous Collections, 67(2):9–59.Google Scholar
Walcott, C. D. 1917b. Cambrian geology and paleontology, 3, fauna of the Mount Whyte Formation. Smithsonian Miscellaneous Collections, 67(3):61–114.Google Scholar
Walcott, C. D. 1924. Cambrian and Ozarkian trilobites. Smithsonian Miscellaneous Collections, 75:53–60.Google Scholar
Westrop, S. R. 1986. Trilobites of the Upper Cambrian Sunwaptan Stage, southern Canadian Rocky Mountains, Alberta. Palaeontographica Canadiana, 3:1–179.Google Scholar
Westrop, S. R. 1992. Upper Cambrian (Marjuman-Steptoean) trilobites from the Port Au Port Group, Western Newfoundland. Journal of Paleontology, 66:228–255.Google Scholar
Westrop, S. R. 1995. Sunwaptan and Ibexian (Upper Cambrian-Lower Ordovician) trilobites of the Rabbitkettle Formation, Mountain River Region, northern Mackenzie Mountains, northwest Canada. Palaeontolographica Canadiana, 12:1–75.Google Scholar
Westrop, S. R., and Ludvigsen, R. 2000. The Late Cambrian (Marjuman) trilobite genus Hysteropleura Raymond from the Cow Head Group, western Newfoundland. Journal of Paleontology, 74:1020–1030.Google Scholar
Whitehouse, F. W. 1939. The Cambrian faunas of north-eastern Australia, Pt. 3, The polymerid trilobites. Memoirs of the Queensland Museum, 11(3):179–282, pls. 19–25.Google Scholar
Yeates, D. K. 1995. Groundplans and exemplars: paths to the tree of life. Cladistics, 11:343–357.Google Scholar