Hostname: page-component-586b7cd67f-vdxz6 Total loading time: 0 Render date: 2024-11-22T05:33:29.707Z Has data issue: false hasContentIssue false
  • English
  • Français

The structure of cranidial shape variation in three early ptychoparioid trilobite species from the Dyeran-Delamaran (traditional “Lower-Middle” Cambrian) boundary interval of Nevada, U.S.A.

Published online by Cambridge University Press:  14 July 2015

Mark Webster
Mark Webster*
Affiliation:
Department of the Geophysical Sciences, University of Chicago, 5734 South Ellis Avenue, Chicago, Illinois 60637,
Get access Rights & Permissions [Opens in a new window]

Abstract

The structure of cranidial shape variation in the early ptychoparioid trilobites Crassifimbra walcotti, Crassifimbra? metalaspis (new combination), and Eokochaspis nodosa is explored using landmark-based geometric morphometric techniques, and is found to be generally similar among the species. Allometry is the strongest single source of cranidial shape variation within each species. The species share several trends in their respective patterns of ontogenetic shape change, but differ in the relative magnitude of these shared trends. Species-specific trends are also present. Each species follows a unique trajectory of ontogenetic shape change. The species exhibit subtle but significant differences in mean cranidial shape even at small size (sagittal length 1.75 mm); the magnitude of interspecific differences becomes larger at larger size (sagittal length 4.2 mm).

For conspecific cranidia of a given size, the major pattern of covariance among anatomical parts is essentially identical to the pattern of covariance among those parts during ontogeny. Developmentally determined covariance patterns among cranidial regions might be responsible for ontogenetic shape change and a portion of non-allometric shape intraspecific variation. Interspecific differences in cranidial shape resulted from complex local modifications to growth pattern and cannot be attributed to simple ontogenetic scaling.

The new collections permit the first description of non-cranidial sclerites of C. walcotti. A cephalic median organ is documented on C. walcotti, representing the oldest known occurrence of this structure in trilobites.

Type
Research Article
Information
Journal of Paleontology , Volume 85 , Issue 2 , March 2011 , pp. 179 - 225
Copyright
Copyright © The Paleontological Society 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Adrain, J. M. and Westrop, S. R.. 2005. Late Cambrian ptychaspidid trilobites from western Utah: implications for trilobite systematics and biostratigraphy. Geological Magazine, 142:377–398.CrossRefGoogle Scholar
Adrain, J. M. and Westrop, S. R.. 2006. New earliest Ordovician trilobite genus Millardicurus: the oldest known hystricurid. Journal of Paleontology, 80:650–671.CrossRefGoogle Scholar
Andresen, P. R., Bookstein, F. L., Conradsen, K., Ersb⊘ll, B., Marsh, J., and Kreiborg, S.. 2000. Surface-bounded growth modeling applied to human mandibles. IEEE Transactions in Medical Imaging, 19:1053–1063.CrossRefGoogle ScholarPubMed
Avise, J. C. 2000. Phylogeography. Harvard University Press, Cambridge, Massachusetts, 447 p.CrossRefGoogle ScholarPubMed
Barrande, J. 1846. Notice préliminaire sur le systême Silurien et les Trilobites de Bohême. Hirschfeld, Leipzig, 97 p.CrossRefGoogle Scholar
Blaker, M. R. and Peel, J. S.. 1997. Lower Cambrian trilobites from North Greenland. Meddelelser om Gr⊘nland, Geoscience, 35:1–145.Google Scholar
Bookstein, F. L. 1991. Morphometric Tools for Landmark Data: Geometry and Biology. Cambridge Univeristy Press, 435 p.Google Scholar
Bookstein, F. L. 1997. Landmark methods for forms without landmarks: morphometrics of group differences in outline shape. Medical Image Analysis, 1:97–118.CrossRefGoogle ScholarPubMed
Bookstein, F. L., Streissguth, A. P., Sampson, P. D., Connor, P. D., and Barr, H. M.. 2002. Corpus callosum shape and neuropsychological deficits in adult males with heavy fetal alcohol exposure. Neuroimage, 15:233–251.CrossRefGoogle ScholarPubMed
Bright, R. C. 1959. A paleoecologic and biometric study of the Middle Cambrian trilobite Elrathia kingii (Meek). Journal of Paleontology, 33:83–98.Google Scholar
Cotton, T. J. 2001. The phylogeny and systematics of blind Cambrian ptychoparioid trilobites. Palaeontology, 44:167–204.CrossRefGoogle Scholar
Dryden, I. L. and Mardia, K. V.. 1998. Statistical Shape Analysis. John Wiley and Sons, Chichester, England, 347 p.Google Scholar
Fortey, R. A. 2001. Trilobite systematics: The last 75 years. Journal of Paleontology, 75:1141–1151.2.0.CO;2>CrossRefGoogle Scholar
France, S. C. 1993. Geographic variation among three isolated populations of the hadal amphipod Hirondellea gigas (Crustacea: Amphipoda: Lysianassoidea). Marine Ecology Progress Series, 92:277–287.CrossRefGoogle 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
Geyer, G. and Malinky, J. M.. 1997. Middle Cambrian fossils from Tizi N'Tichka, the High Atlas, Morocco. Part 1. Introduction and trilobites. Journal of Paleontology, 71:620–637.CrossRefGoogle Scholar
Goodall, C. 1991. Procrustes methods in the statistical analysis of shape. Journal of the Royal Statistical Society, Series B (Methodological), 53:285–339.CrossRefGoogle Scholar
Green, W. D. K. 1996. The thin-plate spline and images with curving features, p. 79–87. In Mardia, K. V., Gill, C. A. and Dryden, I. L. (eds.), Image Fusion and Shape Variability. University of Leeds Press, Leeds.Google Scholar
Gunz, P., Mitteroecker, P., and Bookstein, F. L.. 2005. Semilandmarks in three dimensions, p. 73–98. In Slice, D. E. (ed.), Modern Morphometrics in Physical Anthropology. Kluwer Academic Publishers/Plenum, New York.CrossRefGoogle Scholar
Hall, J. and Whitfield, R. P.. 1877. Palaeontology. United States Geological Exploration of the Fortieth Parallel, 4:198–302.Google Scholar
Hallgrímsson, B. and Hall, B. K.. 2005. Variation: A Central Concept in Biology. Elsevier Academic Press, Burlington, MA, 568 p.Google Scholar
Hopkins, M. J. and Thurman, C. L.. 2010. The geographic structure of morphological variation in eight species of fiddler crabs (Ocypodidae: genus Uca) from the eastern United States and Mexico. Biological Journal of the Linnean Society, 100:248–270.CrossRefGoogle Scholar
Hopkins, M. J. and Webster, M.. 2009. Ontogeny and geographic variation of a new species of the corynexochine trilobite Zacanthopsis (Dyeran, Cambrian). Journal of Paleontology, 83:524–547.CrossRefGoogle Scholar
Hughes, N. C. 1994. Ontogeny, intraspecific variation, and systematics of the Late Cambrian trilobite Dikelocephalus. Smithsonian Contributions to Paleobiology, 79:1–89.CrossRefGoogle Scholar
Hughes, N. C., Minelli, A., and Fusco, G.. 2006. The ontogeny of trilobite segmentation: a comparative approach. Paleobiology, 32:602–627.CrossRefGoogle Scholar
Hunt, G. 2004a. Phenotypic variation in fossil samples: modeling the consequences of time-averaging. Paleobiology, 30:426–443.2.0.CO;2>CrossRefGoogle Scholar
Hunt, G. 2004b. Phenotypic variance inflation in fossil samples: an empirical assessment. Paleobiology, 30:487–506.2.0.CO;2>CrossRefGoogle Scholar
Hunt, G. 2007. Evolutionary divergence in directions of high phenotypic variance in the ostracode genus Poseidonamicus. Evolution, 61:1560–1576.CrossRefGoogle ScholarPubMed
Hupe, P. 1953. Classe de trilobites, p. 22–246. In Piveteau, J. (ed.), Traité de Paléontologie, vol. 3. Les formes ultimes d'Invertébrés: morphologie et évoltion: Onychophores-Arthropodes-Échinodermes-Stomocordés. Masson et Cie, Paris.Google Scholar
Jell, P. A. and Adrain, J. M.. 2003. Available generic names for trilobites. Memoirs of the Queensland Museum, 48:331–553.Google Scholar
Lerosey-Aubril, R. and McNamara, K. J.. 2008. The cephalic median organ of trilobites, p. 229–235. In Rábano, I., Gozalo, R., and García-Bellido, D. (eds.), Advances In Trilobite Research. Cuadernos del Museo Geominero 9. Instituto Geológico y Minero de España, Madrid.Google Scholar
Lochman, C. 1947. Analysis and revision of eleven Lower Cambrian trilobite genera. Journal of Paleontology, 21:59–71.Google Scholar
Matthew, G. F. 1887. Illustrations of the fauna of the St. John Group continued. III–Descriptions of new genera and species, (including a description of a new species of Solenopleura by J. F. Whiteaves). Transactions of the Royal Society of Canada, 3:29–84.Google Scholar
Meek, F. B. 1870. Descriptions of fossils collected by the U.S. Geological Survey, under charge of Clarence King. Proceedings of the Academy of Natural Sciences of Philadelphia, Second Series, 14:56–64.Google Scholar
Nixon, K. C. and Wheeler, Q. D.. 1990. An amplification of the phylogenetic species concept. Cladistics, 6:211–223.CrossRefGoogle 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. 1968. Cambrian trilobites of East-Central Alaska. United States Geological Survey Professional Paper, 559-B:1–115.Google Scholar
Palmer, A. R. 1998a. Terminal Early Cambrian extinction of the Olenellina: Documentation from the Pioche Formation, Nevada. Journal of Paleontology, 72:650–672.CrossRefGoogle Scholar
Palmer, A. R. 1998b. A proposed nomenclature for stages and series for the Cambrian of Laurentia. Canadian Journal of Earth Sciences, 35:323–328.CrossRefGoogle 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. United States Geological Survey Professional Paper, 1047:1–131.Google Scholar
Perez, S. L, Bernal, V., and Gonzalez, P. N.. 2006. Differences between sliding semi-landmark methods in geometric morphometrics, with an application to human craniofacial and dental variation. Journal of Anatomy, 208:769–784.CrossRefGoogle ScholarPubMed
Rasetti, F. 1951. Middle Cambrian stratigraphy and faunas of the Canadian Rocky Mountains. Smithsonian Miscellaneous Collections, 116:1–277.Google Scholar
Rasetti, F. 1955. Lower Cambrian ptychopariid trilobites from the conglomerates of Quebec. Smithsonian Miscellaneous Collections, 128:1–35.Google Scholar
Renaud, S., Auffrey, J.-C., and Michaux, J.. 2006. Conserved phenotypic variation patterns, evolution along lines of least resistance, and departure due to selection in fossil rodents. Evolution, 60:1701–1717.Google ScholarPubMed
Resser, C. E. 1936. Second contribution to nomenclature of Cambrian trilobites. Smithsonian Miscellaneous Collections, 95:1–29.Google Scholar
Resser, C. E. 1937. Third contribution to nomenclature of Cambrian trilobites. Smithsonian Miscellaneous Collections, 95:1–29.Google Scholar
Resser, C. E. 1938. Cambrian System (restricted) of the southern Appalachians. Geological Society of America Special Papers, 15:1–140.Google Scholar
Riska, B. 1981. Morphological variation in the horseshoe crab Limulus polyphemus. Evolution, 35:647–658.Google ScholarPubMed
Rohlf, F. J. 2003. tpsSmall. Version 1.20. Department of Ecology and Evolution, State University of New York. Available at <http://life.bio.sunysb.edu.morph/>..>Google Scholar
Rohlf, F. J. 2009. tpsDig. Version 2.14. Department of Ecology and Evolution, State University of New York. Available at <http://life.bio.sunysb.edu.morph/>..>Google Scholar
Rohlf, F. J. and Slice, D.. 1990. Extensions of the Procrustes method for the optimal superimposition of landmarks. Systematic Zoology, 39:40–59.CrossRefGoogle Scholar
Sampson, P. D., Bookstein, F. L., Sheehan, H., and Bolson, E. L.. 1996. Eigenshape analysis of left ventricular outlines from contrast ventriculograms, p. 131–152. In Marcus, L. F., Corti, M., Loy, A., Naylor, G. J. P. and Slice, D. E. (eds.), Advances in Morphometrics. Nato ASI Series, Series A: Life Science, New York.CrossRefGoogle Scholar
Schluter, D. 1996. Adaptive radiation along genetic lines of least resistance. Evolution, 50:1766–1774.CrossRefGoogle ScholarPubMed
Schwimmer, D. R. 1975. Quantitative taxonomy and biostratigraphy of Middle Cambrian trilobites from Montana and Wyoming. Mathematical Geology, 7:149–166.CrossRefGoogle Scholar
Shaw, A. B. 1957. Quantitative trilobite studies II. Measurement of the dorsal shell of non-agnostidean trilobites. Journal of Paleontology, 31:193–207.Google Scholar
Shaw, A. B. 1962. Paleontology of northwestern Vermont IX. Fauna of the Monkton Quartzite. Journal of Paleontology, 36:322–345.Google Scholar
Sheets, H. D. 2001. Standard6beta. Department of Physics, Canisius College, Buffalo, New York. Available at <http://www.canisius.edu/~sheets/morphsoft.html>.Google Scholar
Sheets, H. D. 2003. VecCompare6c. Department of Physics, Canisius College, Buffalo, New York. Available at <http://www.canisius.edu/~sheets/morphsoft.html>.Google Scholar
Sheets, H. D. 2005. TwoGroup6h. Department of Physics, Canisius College, Buffalo, New York. Available at <http://www.canisius.edu/~sheets/morphsoft.html>.Google Scholar
Sheets, H. D. 2007a. PCAGen6p. Department of Physics, Canisius College, Buffalo, New York. Available at <http://www.canisius.edu/~sheets/morphsoft.html>.Google Scholar
Sheets, H. D. 2007b. DisparityBox6i. Department of Physics, Canisius College, Buffalo, New York. Available at <http://www.canisius.edu/~sheets/morphsoft.html>.Google Scholar
Sheets, H. D. 2008. Regress6N. Department of Physics, Canisius College, Buffalo, New York. Available at <http://www.canisius.edu/~sheets/morphsoft.html>.Google Scholar
Sheets, H. D. 2009. SemiLand6. 7th Beta Version. Department of Physics, Canisius College, Buffalo, New York. Available at <http://www.canisius.edu/~sheets/morphsoft.html>.Google Scholar
Sheets, H. D., Kim, K., and Mitchell, C. E.. 2004. A combined landmark and outline-based approach to ontogenetic shape change in the Ordovician trilobite Triarthrus becki, p. 67–82. In Elewa, A. M. T. (ed.), Morphometrics: Applications in Biology and Paleontology. Springer-Verlag, Berlin.CrossRefGoogle Scholar
Simpson, G. G. 1944. Tempo and Mode in Evolution. Columbia University Press, New York, 237 p.Google Scholar
Slice, D. E. 2007. Geometric morphometrics. Annual Review of Anthropology, 36:261–281.CrossRefGoogle Scholar
Smith, L. H. 1995. The role of species level phenotypic and developmental variability in the early evolution of animals. Unpublished , , 201 p.Google Scholar
Smith, L. H. 1998. Species level phenotypic variation in lower Paleozoic trilobites. Paleobiology, 24:17–36.CrossRefGoogle Scholar
Sniegowski, P. D. and Murphy, H. A.. 2006. Evolvability. Current Biology, 16:R831–R834.CrossRefGoogle ScholarPubMed
Sundberg, F. A. 1999. Redescription of Alokistocare subcoronatum (Hall and Whitfield, 1877), the type species of Alokistocare, and the status of Alokistocaridae Resser, 1939b (Ptychopariida: Trilobita, Middle Cambrian). Journal of Paleontology, 73:1126–1143.CrossRefGoogle Scholar
Sundberg, F. A. 2004. Cladistic analysis of Early-Middle Cambrian kochaspid trilobites (Ptychopariida). Journal of Paleontology, 78:920–940.2.0.CO;2>CrossRefGoogle Scholar
Sundberg, F. A. 2005. The Topazan Stage, a new Laurentian stage (Lincolnian Series-”Middle” Cambrian). Journal of Paleontology, 79:63–71.2.0.CO;2>CrossRefGoogle 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, 74:604–630.2.0.CO;2>CrossRefGoogle Scholar
Sundberg, F. A. and Mccollum, L. B.. 2003. Early and Mid Cambrian trilobites from the outer-shelf deposits of Nevada and California, USA. Palaeontology, 46:945–986.CrossRefGoogle Scholar
Wagner, G. P. and Altenberg, L.. 1996. Complex adaptations and the evolution of evolvability. Evolution, 50:967–976.CrossRefGoogle ScholarPubMed
Walcott, C. D. 1886. Second contribution to the studies on the Cambrian faunas of North America. United States Geological Survey Bulletin, 30, 369 p.Google Scholar
Walcott, C. D. 1890. The fauna of the Lower Cambrian or Olenellus Zone, p. 509–774. In Tenth Annual Report of the Director, 1888-1889, United States Geological Survey.Google Scholar
Walcott, C. D. 1916. Cambrian Geology and Paleontology. III. No. 3. Cambrian Trilobites. Smithsonian Miscellaneous Collections, 64:157–258.Google Scholar
Webster, M. 2007a. A Cambrian peak in morphological variation within trilobite species. Science, 317:499–502.CrossRefGoogle ScholarPubMed
Webster, M. 2007b. Ontogeny and evolution of the Early Cambrian trilobite genus Nephrolenellus (Olenelloidea). Journal of Paleontology, 81:1168–1193.CrossRefGoogle Scholar
Webster, M. 2009. Systematic revision of the Cambrian trilobite Bathynotus Hall, 1860, with documentation of new occurrences in western Laurentia and implications for intercontinental biostratigraphic correlation. Memoirs of the Association of Australasian Palaeontologists, 37:369–406.Google Scholar
Webster, M. and Hughes, N. C.. 1999. Compaction-related deformation in Cambrian olenelloid trilobites and its implications for fossil morphometry. Journal of Paleontology, 73:355–371.CrossRefGoogle Scholar
Webster, M. and Sheets, H. D.. 2010. A practical introduction to landmark-based geometric morphometrics, p. 163–188. In Alroy, J. and Hunt, G. (eds.), Quantitative Methods in Paleobiology. Paleontological Society Papers, Vol. 16.Google Scholar
Webster, M. and Zelditch, M. L.. 2005. Evolutionary modifications of ontogeny: heterochrony and beyond. Paleobiology, 31:354–372.CrossRefGoogle Scholar
Webster, M. and Zeldtich, M. L.. 2008. Integration and regulation of developmental systems in trilobites, p. 427–433. In Rábano, I., Gozalo, R., and García-Bellido, D. (eds.), Advances In Trilobite Research. Cuadernos del Museo Geominero 9. Instituto Geológico y Minero de España, Madrid.Google Scholar
Webster, M. and Zelditch, M. L.. 2009. Testing hypotheses of developmental constraints on macroevolutionary diversification: Studying modularity of ancient developmental systems. Cincinnati Museum Center Scientific Contributions Number, 3:115.Google Scholar
Webster, M., Sheets, H. D., and Hughes, N. C.. 2001. Allometric patterning in trilobite ontogeny: testing for heterochrony in Nephrolenellus, p. 105–144. In Zelditch, M. L. (ed.), Beyond Heterochrony: The Evolution of Development. Wiley and Sons, New York.Google Scholar
Webster, M., Gaines, R. R., and Hughes, N. C.. 2008. Microstratigraphy, trilobite biostratinomy, and depositional environment of the “Lower Cambrian” Ruin Wash Lagerstätte, Pioche Formation, Nevada. Palaeogeography, Palaeoclimatology, Palaeoecology, 264:100–122.CrossRefGoogle Scholar
Westrop, S. R. and Adrain, J. M.. 2007. Bartonaspis new genus, a trilobite species complex from the base of the Upper Cambrian Sunwaptan Stage in North America. Canadian Journal of Earth Sciences, 44:987–1003.CrossRefGoogle Scholar
Wheeler, Q. D. and Meier, R.. 2000. Species Concepts and Phylogenetic Theory: A Debate. Columbia University Press, New York, 230 p.Google Scholar
Whittington, H. B. 1965. Trilobites of the Ordovician Table Head Formation, western Newfoundland. Bulletin of the Museum of Comparative Zoology, 132:277–442.Google Scholar
Whittington, H. B., Chatterton, B. D. E., Speyer, S. E., Fortey, R. A., Owens, R. M., Chang, W. T., Dean, W. T., Jell, P. A., Laurie, J. R., Palmer, A. R., Repina, L. N., Rushton, A. W. A., Shergold, J. H., Clarkson, E. N. K., Wilmot, N. V., and Kelly, S. R. A.. 1997. Treatise on Invertebrate Paleontology. Part O. Arthropoda 1. Trilobita, Revised. Volume 1: Introduction, Order Agnostida, Order Redlichiida. Geological Society of America and Univeristy of Kansas, Boulder, Colorado and Lawrence, Kansas, 530 p.Google Scholar
Zelditch, M. L., Swiderski, D. L., Sheets, H. D., and Fink, W. L.. 2004. Geometric Morphometrics of Biologists: A Primer. Elsevier Academic Press, San Diego, 443 p.Google Scholar