Hostname: page-component-7c8c6479df-24hb2 Total loading time: 0 Render date: 2024-03-27T15:44:48.581Z Has data issue: false hasContentIssue false

The world's biggest trilobite—Isotelus rex new species from the upper Ordovician of northern Manitoba, Canada

Published online by Cambridge University Press:  20 May 2016

David M. Rudkin
Affiliation:
Department of Paleobiology, Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario M5S 2C6, Canada,
Graham A. Young
Affiliation:
The Manitoba Museum, 190 Rupert Avenue, Winnipeg, Manitoba R3B 0N2, Canada
Robert J. Elias
Affiliation:
Department of Geological Sciences, The University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
Edward P. Dobrzanski
Affiliation:
The Manitoba Museum, 190 Rupert Avenue, Winnipeg, Manitoba R3B 0N2, Canada

Abstract

The largest known trilobite fossil, a virtually complete articulated dorsal shield of the asaphid Isotelus rex new species, has been recovered from Upper Ordovician (Cincinnatian, Richmondian) nearshore carbonates of the Churchill River Group in northern Manitoba. At over 700 mm in length, it is almost 70 percent longer than the largest previously documented complete trilobite, and provides the first unequivocal evidence of maximum trilobite length in excess of one-half metre. Comparisons with other fossil and extant members of the phylum suggest that in terms of maximum linear dimensions it was among the biggest arthropods ever to have lived. Sediments of the Churchill River Group were deposited in an equatorial epeiric setting and the extremely large size of I. rex n. sp. thus marks a striking example of low-latitude gigantism, in sharp contrast to the widespread phenomenon of “polar gigantism” in many modern marine benthic arthropods. Lack of extensive epibiontic colonization of the exoskeletal surface and the presence of large distinctive trace fossils in the same unit suggest that I. rex n. sp. may have been a semi-infaunal predator and scavenger that employed a shallow furrowing and probing mode of benthic feeding. The extinction of the isotelines (and virtually the entire asaphide lineage) at the end of the Ordovician cannot be related to the near contemporaneous achievement of exceptionally large adult size in some representatives. Failure to survive the terminal Ordovician extinction event was most likely a consequence of a pelagic larval life-style that proved ill-adapted to the rapid onset of global climatic cooling and loss of tropical shelf habitats.

Type
Research Article
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

Abele, L. G. 1982. Biogeography, p. 241304. In Bliss, D. E. (ed.), The Biology of Crustacea, Volume 1, Systematics, the Fossil Record, and Biogeography (edited by Abele, L. G.). Academic Press, New York.Google Scholar
Alexander, R. M. 1998. All-time giants: the largest animals and their problems. Palaeontology, 41:12311245.Google Scholar
Atkinson, D., and Sibly, R. M. 1997. Why are organisms usually bigger in colder environments? Making sense of a life history puzzle. Trends in Ecology and Evolution, 12:235239.CrossRefGoogle ScholarPubMed
Benton, M. J. 1990. Evolution of large size, p. 147152. In Briggs, D. E. G. and Crowther, P. R. (eds.), Paleobiology—A Synthesis. Blackwell, London.Google Scholar
Blanckenhorn, W. U. 2000. The evolution of body size: What keeps organisms small? The Quarterly Review of Biology, 75:385407.CrossRefGoogle ScholarPubMed
Bliss, D. E. 1990. Shrimps, Lobsters and Crabs. Columbia University Press, New York, 242 p.Google Scholar
Brenchley, P. J., Marshall, J. D., Carden, G. A. F., Robertson, D. B. R., Long, D. G. F., Meidla, T., Hints, L., and Anderson, T. F. 1994. Bathymetric and isotopic evidence for a short-lived Ordovician glaciation in a greenhouse period. Geology, 22:295298.2.3.CO;2>CrossRefGoogle Scholar
Briggs, D. E. G. 1985. Gigantism in Palaeozoic arthropods, p. 157. In Cope, J. C. W. and Skelton, P. W. (eds.), Evolutionary Case Histories from the Fossil Record. Special Papers in Palaeontology, 33.Google Scholar
Briones-Fourzan, P., and Lozano-Alvarez, E. 1991. Aspects of the biology of the giant isopod Bathynomus giganteus A. Milne Edwards, 1879 (Flabellifera: Cirolanidae), off the Yucatan Peninsula. Journal of Crustacean Biology, 11:375385.CrossRefGoogle Scholar
Burmeister, H. 1843. Die organisation der Trilobiten. Georg Reimer, Berlin, 147 p.Google Scholar
Bush, G. L. 1993. A reaffirmation of Santa Rosalia, or why are there so many kinds of small animals?, p. 229249. In Lees, D. R. and Edwards, D. (eds.), Evolutionary Patterns and Processes. Linnean Society Symposium Series, No. 14, Academic Press, London.Google Scholar
Campbell, D. G. 1992. The bottom of the bottom of the world. Natural History, 101(11):4653.Google Scholar
Chapelle, G., and Peck, L. S. 1999. Polar gigantism dictated by oxygen availability. Nature, 399:114115.CrossRefGoogle Scholar
Chatterton, B. D. E., and Speyer, S. E. 1989. Larval ecology, life history strategies, and patterns of extinction and survivorship among Ordovician trilobites. Paleobiology, 15:118132.CrossRefGoogle Scholar
Chatterton, B. D. E., Siveter, D. J., Edgecombe, G. D., and Hunt, A. S. 1990. Larvae and relationships of the Calymenina (Trilobita). Journal of Paleontology, 64:255277.CrossRefGoogle Scholar
Chen, J.-Y., Ramsköld, L., and Zhou, G.-Q. 1994. Evidence for monophyly and arthropod affinity of Cambrian giant predators. Science, 264:13041308.CrossRefGoogle ScholarPubMed
Clarke, J. M., and Ruedemann, R. 1912. The Eurypterida of New York. New York State Museum, Memoir 14, 439 p.Google Scholar
Coleman, N. 1991. Encyclopedia of Marine Animals. HarperCollins, New York, 323 p.Google Scholar
Colin, P. L., and Arneson, C. 1995. Tropical Pacific Invertebrates. Coral Reef Press, Beverly Hills, 296 p.Google Scholar
Curry, G. B. 1984. Brachiopod growth and climate, p. 7583. In Brenchley, P. J. (ed.), Fossils and Climate. John Wiley and Sons, New York.Google Scholar
Dalingwater, J. E., and Mutvei, H. 1990. Arthropod exoskeletons, p. 8396. In Carter, J. G. (ed.), Skeletal Biomineralization: Patterns, Processes and Evolutionary Trends, Volume 1. Van Nostrand Reinhold, New York.Google Scholar
Dekay, J. E. 1824. Observations on the structure of trilobites, and descriptions of an apparently new genus. With notes on the geology of Trenton Falls by J. Renwick. Annals of the Lyceum of Natural History of New York, 1:174189.Google Scholar
Dudley, R. 1998. Atmospheric oxygen, giant Paleozoic insects and the evolution of aerial locomotor performance. Journal of Experimental Biology, 201:10431050.CrossRefGoogle ScholarPubMed
Elias, R. J., Young, G. A., Nowlan, G. S., Dobrzanski, E. P., and Rudkin, D. M. 1999. Ordovician-Silurian boundary section discovered near Churchill, Manitoba: preliminary report, p. 229232. In Kraft, P. and Fatka, O. (eds.), Quo vadis Ordovician? Acta Universitatis Carolinae, Geologica, 43(1/2).Google Scholar
Fagerstrom, J. A. 1983. Diversity, speciation, endemism and extinction in Devonian reef and level-bottom communities, eastern North America. Coral Reefs, 2:6570.CrossRefGoogle Scholar
Foerste, A. 1919. Notes on Isotelus, Acrolichas, Calymene, and Encrinurus . Denison University Bulletin, 19:6581.Google Scholar
Foote, M., and Sepkoski, J. J. Jr. 1999. Absolute measures of the completeness of the fossil record. Nature, 398:415417.CrossRefGoogle ScholarPubMed
Ford, S. M. 1999. Phyletic dwarfism and gigantism, p. 880883. In Singer, R. (ed.), Encyclopedia of Paleontology. Fitzroy Dearborn Publishers, Chicago.Google Scholar
Fortey, R. A. 2000. Olenid trilobites: the oldest known chemautotrophic symbionts? Proceedings of the National Academy of Sciences, 97:65746578.CrossRefGoogle Scholar
Fortey, R. A., and Chatterton, B. D. E. 1988. Classification of the trilobite suborder Asaphina. Palaeontology, 31:165222.Google Scholar
Fortey, R. A., and Owens, R. M. 1999a. The trilobite exoskeleton, p. 537562. In Savazzi, E. (ed.), Functional Morphology of the Invertebrate Skeleton. John Wiley and Sons Ltd., Chichester.Google Scholar
Fortey, R. A., and Owens, R. M. 1999b. Feeding habits in trilobites. Palaeontology, 42:429465.CrossRefGoogle Scholar
Fortey, R. A., and Seilacher, A. 1997. The trace fossil Cruziana semiplicata and the trilobite that made it. Lethaia, 30:105112.CrossRefGoogle Scholar
Frey, R. C. 1987. The paleoecology of a Late Ordovician shale unit from southwest Ohio and southeastern Indiana. Journal of Paleontology, 61:242267.CrossRefGoogle Scholar
Frey, R. C. 1989. Paleoecology of a well-preserved nautiloid assemblage from a Late Ordovician shale unit, southwestern Ohio. Journal of Paleontology, 63:604620.CrossRefGoogle Scholar
Frey, R. C. 1995. Middle and Upper Ordovician nautiloid cephalopods of the Cincinnati Arch region of Kentucky, Indiana, and Ohio. United States Geological Survey Professional Paper, 1066-P, 126 p.CrossRefGoogle Scholar
Gans, C., Dudley, R., Aguilar, N. M., and Graham, J. B. 1999. Late Paleozoic atmospheres and biotic evolution. Historical Biology, 13:199219.CrossRefGoogle Scholar
Geist, V. 1987. Bergmann's rule is invalid. Canadian Journal of Zoology, 65:10351038.CrossRefGoogle Scholar
Geist, V. 1990. Bergmann's rule is invalid: a reply to J. D. Paterson. Canadian Journal of Zoology, 68:16131615.CrossRefGoogle Scholar
Geyer, G. 1993. The giant Cambrian trilobites of Morocco. Beringeria, 8:71107.Google Scholar
Gibbs, M. T., Barron, E. J., Crowley, T. J., and Kump, L. R. 1995. Model sensitivity of the Late Ordovician climate to atmospheric pCO2 , p. 297298. In Cooper, J. D., Droser, M. L., and Finney, S. C. (eds.), Ordovician Odyssey. Society of Economic Paleontologists and Mineralogists, Pacific Section, Book 77.Google Scholar
Graham, J. B., Dudley, R., Aguilar, N. M., and Gans, C. 1995. Implications of the late Paleozoic oxygen pulse for physiology and evolution. Nature, 375:117120.CrossRefGoogle Scholar
Hallam, A. 1975. Evolutionary size increase and longevity in Jurassic bivalves and ammonites. Nature, 258:493496.CrossRefGoogle Scholar
Hansen, M. C. 1985. Isotelus—Ohio's state fossil. Ohio Geology Newsletter (Summer 1985):14.Google Scholar
Hansen, M. C. 1989. Large Isotelus found: Ohio Geology Newsletter (Spring 1989):6.Google Scholar
Hartnoll, R. G. 1982. Growth, p. 111196. In Bliss, D. E. (ed.), The Biology of Crustacea, Volume 2, Embryology, Morphology, and Genetics (edited by Abele, L. G.). Academic Press, New York.Google Scholar
Henry, J.-L. 1989. Paléoenvironments et dynamique de faunes de trilobites dans l'Ordovicien (Llanvirn Supérieur-Caradoc Basal) du Massif Armoricain (France). Palaeogeogeography, Palaeoclimatology, Palaeoecology, 73:139153.CrossRefGoogle Scholar
Jablonski, D. 1996. Body size and macroevolution, p. 256289. In Jablonski, D., Irwin, D. H., and Lipps, J. H. (eds.), Evolutionary Paleobiology. University of Chicago Press, Chicago.Google Scholar
Johnson, M. E., Skinner, D. F., and MacLeod, K. G. 1988. Ecological zonation during the carbonate transgression of a Late Ordovician rocky shore (northeastern Manitoba, Hudson Bay, Canada). Palaeogeography, Palaeoclimatology, Palaeoecology, 65:93114.CrossRefGoogle Scholar
Johnson, T. 1985. Trilobites of the Thomas T. Johnson Collection. Privately published, Dayton, Ohio, 178 p.Google Scholar
Kaesler, R. L. (ed.). 1992. Treatise on Invertebrate Paleontology, Pt. R, Arthropoda 4, Hexapoda, Volume 3. Geological Society of America and University of Kansas Press, Lawrence, 277 p.Google Scholar
Kaesler, R. L. (ed.). 1997. Treatise on Invertebrate Paleontology, Pt. O, Arthropoda 1, Trilobita, Revised, Volume 1. Geological Society of America and University of Kansas Press, Lawrence, 530 p.Google Scholar
Key, M. M. Jr., Jeffries, W. B., Voris, H. K., and Yang, C. M. 1996. Epizoic bryozoans, horseshoe crabs, and other mobile benthic substrates. Bulletin of Marine Science, 58:368384.Google Scholar
Kloc, G. J. 1993. Epibionts on Selenopeltinae (Odontopleurida) trilobites. Geological Society of America Abstracts with Programs, 25(6):103.Google Scholar
Lespérance, P. J. 1985. Faunal distributions across the Ordovician-Silurian boundary, Anticosti Island and Percé, Québec, Canada. Canadian Journal of Earth Sciences, 22:838849.CrossRefGoogle Scholar
Locke, J. 1838. Geological report (on southwestern Ohio). Ohio Geological Survey, 2nd Annual Report, p. 210286.Google Scholar
Locke, J. 1842. On a new species of trilobite of very large size (Isotelus megistos). American Journal of Science, 42:366368.Google Scholar
Manger, W. L., Meeks, L. K., and Stephen, D. A. 1999. Pathologic gigantism in Middle Carboniferous cephalopods, southern midcontinent, United States, p. 7789. In Olóriz, F. and Rodríguez-Tovar, F. J. (eds.), Advancing Research on Living and Fossil Cephalopods. Kluwer Academic/Plenum Publishers, New York.CrossRefGoogle Scholar
Meyer-Rochow, V. B. 1980. Cuticular surface structures in Glyptonotus antarcticus—a marine isopod from the Ross Sea (Antarctica). Zoomorphologie, 94:209216.CrossRefGoogle Scholar
McGowan, C. 1994. Diatoms to Dinosaurs: The Scale and Size of Living Things. Penguin Books Ltd., London, 288 p.Google Scholar
McKinney, M. L. 1990. Trends in body-size evolution, p. 75118. In McNamara, K. J. (ed.), Evolutionary Trends. Belhaven Press, London.Google Scholar
Moore, R. C. (ed.). 1959. Treatise on Invertebrate Paleontology, Pt. O, Arthropoda 1. Geological Society of America and University of Kansas Press, Lawrence, 560 p.Google Scholar
Mousseau, T. A. 1997. Ectotherms follow the converse to Bergmann's rule. Evolution, 51:630632.CrossRefGoogle ScholarPubMed
Mukai, H. 1979. A new giant amphipod belonging to a new genus, Megaceradocus, found in the Japan Sea. Bulletins of the National Science Museum, Tokyo, Series A, 5:175181.Google Scholar
Mukai, H., and Takeda, M. 1987. A giant amphipod crustacea from the Miocene Morozaki Group in the Chita Peninsula, central Japan. Bulletins of the National Science Museum, Tokyo, Series C, 13:3539.Google Scholar
Nelson, S. J., and Johnson, R. D. 1966. Geology of Hudson Bay Basin. Bulletin of Canadian Petroleum Geology, 14:520578.Google Scholar
Norford, B. S. 1971. Silurian stratigraphy of northern Manitoba, p. 199207. In Turnock, A. C. (ed.), Geoscience Studies in Manitoba. Geological Association of Canada, Special Paper 9.Google Scholar
Norris, A. W., and Sanford, B. V. 1969. Paleozoic and Mesozoic geology of the Hudson Bay Lowlands, p. 169205. In Hood, P. J. (ed.), Earth Science Symposium on Hudson Bay. Geological Survey of Canada, Paper 68-53.Google Scholar
Osgood, R. G. 1970. Trace fossils of the Cincinnati area. Palaeontographica Americana, 6:281444.Google Scholar
Owen, A. W. 1986. The uppermost Ordovician (Hirnantian) trilobites of Girvan, SW Scotland with a review of coeval trilobite faunas. Transactions of the Royal Society of Edinburgh, 77:231239.CrossRefGoogle Scholar
Palmer, A. R. 1981. Do carbonate skeletons limit the rate of body growth? Science, 292:150152.Google Scholar
Partridge, L., and Coyne, J. A. 1997. Bergmann's rule in ectotherms: is it adaptive? Evolution, 51:632635.CrossRefGoogle ScholarPubMed
Paterson, J. D. 1990. Comment—Bergmann's rule is invalid: a reply to V. Geist. Canadian Journal of Zoology, 68:16101612.CrossRefGoogle Scholar
Plotnick, R. E. 1990. Paleobiology of the arthropod cuticle, p. 177196. In Culver, S. J. (Series ed.), Arthropod Paleobiology. Short Courses in Paleontology 3, Paleontological Society, Knoxville.Google Scholar
Przibram, H. 1931. Connecting laws of animal morphology. Four lectures held at the University of London, March, 1929. London University Press, London, 62 p.Google Scholar
Rabano, I. 1989. El género Uralichas Delgado, 1892 (Trilobite, Lichaida) en al Ordovícico de la Península Ibérica. Boletín Geológico y Minero, 100(1):2147.Google Scholar
Raymond, P. E. 1913. Description of some new Asaphidae. Victoria Memorial Museum Bulletin, 1:4148.Google Scholar
Reimann, I. G. 1942. A new restoration of Terataspis . Bulletin of the Buffalo Society of Natural Sciences, 17:3951.Google Scholar
Rolfe, W. D. I., and Ingham, J. K. 1967. Limb structure and diet of the Carboniferous centipede Arthropleura . Scottish Journal of Geology, 3:118124.CrossRefGoogle Scholar
Rudkin, D. M., and Tripp, R. P. 1989. The type species of the Ordovician trilobite Isotelus: I. gigas . Life Sciences Contribution, Royal Ontario Museum, Toronto, 152, 18 p.Google Scholar
Sanford, B. V., Norris, A. W., and Bostock, H. H. 1968. Geology of the Hudson Bay Lowlands (Operation Winisk). Geological Survey of Canada, Paper 67-60:145.CrossRefGoogle Scholar
Scotese, C. R., and McKerrow, W. S. 1990. Revised world maps and introduction, p. 121. In McKerrow, W. S. and Scotese, C. R. (eds.), Palaeozoic Palaeogeography and Biogeography. Geological Society of London, Memoir 12.Google Scholar
Scotese, C. R. and McKerrow, W. S. 1991. Ordovician plate tectonic reconstructions, p. 271282. In Barnes, C. R. and Williams, S. H. (eds.), Advances in Ordovician Geology. Geological Survey of Canada, Paper 90-9.Google Scholar
Segonzac, M., Laurent, M. De Saint, and Casanova, B. 1994. L'enigme du comportement trophique des crevettes Alvinocarididae des sites hydrothermaux de la dorsale medio-atlantique. Cahiers de Biologie Marine, 34:535571.Google Scholar
Selden, P. A. 1983. The biggest spider. Newsletter of the British Arachnology Society, Number 36:45.Google Scholar
Selden, P. A. 1984. Autecology of Silurian eurypterids, p. 3954. In Basset, M. G. and Lawson, J. D. (eds.), Autecology of Silurian Organisms. Special Papers in Palaeontology, 32.Google Scholar
Selden, P. A. 1993. Arthropoda (Aglaspida, Pychnogonida and Chelicerata), p. 297320. In Benton, M. J. (ed.), The Fossil Record 2. Chapman & Hall, London.Google Scholar
Skinner, D. F., and Johnson, M. E. 1987. Nautiloid debris oriented by long-shore currents along a Late Ordovician-Early Silurian rocky shore. Lethaia, 20:157164.CrossRefGoogle Scholar
Speyer, S. E., and Chatterton, B. D. E. 1990. Trilobite larvae, larval ecology and developmental biology, p. 137156. In Culver, S. J. (Series ed.), Arthropod Paleobiology. Short Courses in Paleontology 3, Paleontological Society, Knoxville.Google Scholar
Springthorpe, R. T. 1990. Coconut crabs. Australian Natural History, 23:682.Google Scholar
Stanley, D. C. A., and Pickerill, R. K. 1998. Systematic ichnology of the Late Ordovician Georgian Bay Formation of southern Ontario, eastern Canada. Life Sciences Contribution, Royal Ontario Museum, Toronto, 162, 56 p.Google Scholar
Stanley, S. M. 1973. An explanation for Cope's Rule. Evolution, 27:126.CrossRefGoogle ScholarPubMed
Stanley, S. M., and Hardie, L. A. 1998. Secular oscillations in the carbonate mineralogy of reef-building and sediment-producing organisms driven by tectonically forced shifts in seawater chemistry. Palaeogeography, Palaeoclimatology, Palaeoecology, 144:319.CrossRefGoogle Scholar
Stanley, S. M., and Hardie, L. A. 1999. Hypercalcification: paleontology links plate tectonics and geochemistry to sedimentology. GSA Today, 9:17.Google Scholar
Steele, D. H. 1983. Size compositions of lysianassid amphipods in cold and warm water habitats, p. 113119. In Lowry, J. K. (ed.), Papers from the Conference on the Biology and Evolution of Crustacea. The Australian Museum, Memoir 18, Sydney.Google Scholar
Stevens, G. R. 1988. Giant ammonites: a review, p. 141166. In Wiedmann, J. and Kullmann, J. (eds.), Cephalopods—Present and Past. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart.Google Scholar
Sutcliffe, O. E., Dowdeswell, J. A., Whittington, R. J., Theron, J. N., and Craig, J. 2000. Calibrating the Late Ordovician glaciation and mass extinction by the eccentricity cycles of Earth's orbit. Geology, 28:967970.2.0.CO;2>CrossRefGoogle Scholar
Tetreault, D. K. 1992. Paleoecologic implications of epibionts on the Silurian lichid trilobite Arctinurus . Fifth North American Paleontology Convention, Abstracts and Program, Paleontological Society Special Publication 6:289.CrossRefGoogle Scholar
Thomas, A. T., and Holloway, D. J. 1988. Classification and phylogeny of the trilobite order Lichida. Philosophical Transactions of the Royal Society of London, B 321:179262.Google Scholar
Trammer, J., and Kaim, A. 1997. Body size and diversity exemplified by three trilobite clades. Acta Palaeontologica Polonica, 42:112.Google Scholar
Van der Voo, R. 1988. Paleozoic paleogeography of North America, Gondwana, and intervening displaced terranes: comparisons of paleomagnetism with paleoclimatology and biogeographical patterns. Geological Society of America, Bulletin, 100:311324.2.3.CO;2>CrossRefGoogle Scholar
van Voorhies, W. A. 1996. Bergmann size clines: a simple explanation for their occurrence in ectotherms. Evolution, 50:12591264.CrossRefGoogle ScholarPubMed
van Voorhies, W. A. 1997. On the adaptive nature of Bergmann size clines: a reply to Mousseau, Partridge and Coyne. Evolution, 51:635640.CrossRefGoogle ScholarPubMed
Waterston, C. D., Oelofsen, B. W., and Oosthuizen, R. D. F. 1985. Cyrtoctenus wittebergensis sp. nov. (Chelicerata: Eurypterida), a large sweep-feeder from the Carboniferous of South Africa. Transactions of the Royal Society of Edinburgh. Earth Sciences, 76:339358.Google Scholar
Wetzer, R. 1986. Bathynomus: a living sea monster. Terra, 25:2629.Google Scholar
Whittington, H. B. 1992. Fossils Illustrated, Volume 2, Trilobites. The Boydell Press, Woodbridge, 145 p.Google Scholar
Wills, M. A., Briggs, D. E. G., and Fortey, R. A. 1998. Evolutionary correlates of arthropod tagmosis: scrambled legs, p. 5765. In Fortey, R. A. and Thomas, R. H. (eds.), Arthropod Relationships. Chapman & Hall, London.CrossRefGoogle Scholar
Wilson, H. M., and Shear, W. A. 2000. Microdecemlicida, a new order of minute arthropleurideans (Arthropoda: Myriapoda) from the Devonian of New York State, U.S.A. Transactions of the Royal Society of Edinburgh: Earth Sciences, 90:351375.CrossRefGoogle Scholar
Wolosz, T. H. 1992. Patterns of reef growth in the Middle Devonian Edgecliff Member of the Onondaga Formation of New York and Ontario, Canada, and their ecological significance. Journal of Paleontology, 66:815.CrossRefGoogle Scholar
Wolosz, T. H., and Paquette, D. E. 1988. Middle Devonian reefs of the Edgecliff Member of the Onondaga Formation of New York, p. 531539. In McMillan, N. J., Embry, A. F., and Glass, D. J. (eds.), Devonian of the World, Proceedings of the Second International Symposium on the Devonian System, Volume II, Sedimentation. Canadian Society of Petroleum Geologists Memoir 14, Calgary.Google Scholar
Wood, G. L. 1979. Animal Facts and Feats. Sterling, New York, 256 p.Google Scholar
Yamaski, T. 1988. External morphology, p. 69104. In Sekiguchi, K. (ed.), Biology of Horseshoe Crabs. Science House, Tokyo.Google Scholar
Yonge, C. M. 1975. Giant clams. Scientific American, 232:96105.CrossRefGoogle ScholarPubMed