Hostname: page-component-78c5997874-v9fdk Total loading time: 0 Render date: 2024-11-18T13:17:37.147Z Has data issue: false hasContentIssue false
  • English
  • Français

Diversification of atypical paleozoic echinoderms: a quantitative survey of patterns of stylophoran disparity, diversity, and geography

Published online by Cambridge University Press:  08 April 2016

Bertrand Lefebvre ,
Gunther J. Eble ,
Nicolas Navarro  and
Bruno David
Bertrand Lefebvre
Affiliation:
Centre National de la Recherche Scientifique, UMR 5561 Biogéosciences, Université de Bourgogne, 6 boulevard Gabriel, 21000 Dijon, France. E-mail: [email protected]
Gunther J. Eble
Affiliation:
Centre National de la Recherche Scientifique, UMR 5561 Biogéosciences, Université de Bourgogne, 6 boulevard Gabriel, 21000 Dijon, France. E-mail: [email protected]
Nicolas Navarro
Affiliation:
Centre National de la Recherche Scientifique, UMR 5561 Biogéosciences, Université de Bourgogne, 6 boulevard Gabriel, 21000 Dijon, France
Bruno David
Affiliation:
Centre National de la Recherche Scientifique, UMR 5561 Biogéosciences, Université de Bourgogne, 6 boulevard Gabriel, 21000 Dijon, France. E-mail: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

The analysis of morphological disparity and of morphospace occupation through the macroevolutionary history of clades is now a major research program in paleobiology, and increasingly so in organismal and comparative biology. Most studies have focused on the relationship between taxonomic diversity and morphological disparity, and on ecological or developmental controls. However, the geographic context of diversification has remained understudied. Here we address geography quantitatively. Diversity, disparity, and paleogeographic dispersion are used to describe the evolutionary history of an extinct echinoderm clade, the class Stylophora (cornutes, mitrates), from the Middle Cambrian to the Middle Devonian (about 128 Myr subdivided into 12 stratigraphic intervals). Taxonomic diversity is estimated from a representative sample including 73.3% of described species and 92.4% of described genera. Stylophoran morphology is quantified on the basis of seven morphometric parameters derived from image analysis of homologous skeletal regions. Three separate principal coordinates analyses (PCO) are performed for thecal outlines, plates from the lower thecal surface, and plates from the upper thecal surface, respectively. PCO scores from these three separate analyses are then used as variables for a single, global, meta-PCO. For each time interval, disparity is calculated as the sum of variance in the multidimensional morphospace defined by the meta-PCO axes. For each time interval, a semiquantitative index of paleogeographic dispersion is calculated, reflecting both global (continental) and local (regional) aspects of dispersion.

Morphospace occupation of cornutes and mitrates is partly overlapping, suggesting some morphologic convergences between the two main stylophoran clades, probably correlated to similar modes of life (e.g., symmetrical cornutes and primitive mitrocystitids). Hierarchical clustering allowed the identification of three main morphological sets (subdivided into 11 subsets) within the global stylophoran morphospace. These morphological sets are used to analyze the spatiotemporal variations of disparity. The initial radiation of stylophorans is characterized by a low diversity and a rapid increase in disparity (Middle Cambrian–Tremadocian). The subsequent diversification involved filling and little expansion of morphospace (Arenig–Middle Ordovician). Finally, both stylophoran diversity and disparity decreased relatively steadily from the Late Ordovician to the Middle Devonian, with the exception of a second (lower) peak in the Early Devonian. Such a pattern is comparable to that of other Paleozoic marine invertebrates such as blastozoans and orthid brachiopods. During the Lower to Middle Ordovician, the most dramatic diversification of stylophorans took place with a paleogeographic dispersion essentially limited to the periphery of Gondwana. In the Late Ordovician, stylophorans steadily extended toward lower paleolatitudes, and new environmental conditions, where some of them radiated, and finally survived the end-Ordovician mass extinction (e.g., anomalocystitids). This pattern of paleobiogeographic dispersion is comparable to that of other examples of Paleozoic groups of marine invertebrates, such as bivalve mollusks.

Type
Articles
Information
Paleobiology , Volume 32 , Issue 3 , Summer 2006 , pp. 483 - 508
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

Literature Cited

Babin, C. 1993. Rôle des plates-formes gondwaniennes dans les diversifications des mollusques bivalves durant l'Ordovicien. Bulletin de la Société Géologique de France 164:141–153.Google Scholar
Beisswenger, M. 1994. A calcichordate interpretation of the new mitrate Eumitrocystella savilli from the Ordovician of Morocco. Paläontologische Zeitschrift 68:443–462.Google Scholar
Bergström, J., Naumann, W. W., Viehweg, J., and Martí-Mus, M. 1998. Conodonts, calcichordates and the origin of vertebrates. Mitteilungen aus dem Museum für Naturkunde in Berlin, Geowissenschaftliche Reihe 1:81–92.Google Scholar
Bookstein, F. L. 1994. Can biometrical shape be a homologous character? Pp. 197–227in Hall, B. K., ed. Homology: the hierarchical basis of comparative biology. Academic Press, San Diego.Google Scholar
Briggs, D. E. G., Fortey, R. A., and Wills, M. A. 1992. Morphological disparity in the Cambrian. Science 256:1670–1673.Google Scholar
Carlson, S. J. 1992. Evolutionary trends in the articulate brachiopod hinge mechanism. Paleobiology 18:344–366.Google Scholar
Caster, K. E. 1983. A new Silurian carpoid echinoderm from Tasmania and a revision of the Allanicytidiidae. Alcheringa 7:321–335.Google Scholar
Chauvel, J. 1941. Recherches sur les cystoïdes et les carpoïdes armoricains. Mémoires de la Société Géologique et Minéralogique de Bretagne 5:1–286.Google Scholar
Chauvel, J. 1966. Echinodermes de l'Ordovicien du Maroc. Editions du CNRS, Paris.Google Scholar
Chauvel, J. 1981. Etude critique de quelques échinodermes stylophores du Massif armoricain. Bulletin de la Société Géologique et Minéralogique de Bretagne C 13:67–101.Google Scholar
Cocks, L. R. M., and Fortey, R. A. 1990. Biogeography of Ordovician and Silurian faunas. Pp. 97–104in McKerrow, and Scotese, 1990.Google Scholar
Cocks, L. R. M., McKerrow, W. S., and Van Staal, C. R. 1997. The margins of Avalonia. Geological Magazine 134:627–636.Google Scholar
Morris, S. Conway 1998. The crucible of creation. Oxford University Press, Oxford.Google Scholar
Cope, J. C. W. 2004. Bivalve and rostroconch mollusks. Pp. 196–208in Webby, et al. 2004b.CrossRefGoogle Scholar
Cope, J. C. W., and Babin, C. 1999. Diversification of bivalves in the Ordovician. Geobios 32:175–185.Google Scholar
Craske, A. J., and Jefferies, R. P. S. 1989. A new mitrate from the Upper Ordovician of Norway and a new approach to subdividing a plesion. Palaeontology 32:69–99.Google Scholar
Cripps, A. P. 1988. A new species of stem-group chordate from the Upper Ordovician of Northern Ireland. Palaeontology 31:1053–1077.Google Scholar
Cripps, A. P. 1989a. A new stem-group chordate (Cornuta) from the Llandeilo of Czechoslovakia and the cornute-mitrate transition. Zoological Journal of the Linnean Society 96:49–85.CrossRefGoogle Scholar
Cripps, A. P. 1989b. A new genus of stem chordate (Cornuta) from the Lower and Middle Ordovician of Czechoslovakia and the origin of bilateral symmetry in the chordates. Geobios 22:215–245.CrossRefGoogle Scholar
Cripps, A. P. 1990. A new stem-craniate from the Ordovician of Morocco and the search for the sister group of the Craniata. Zoological Journal of the Linnean Society 100:27–71.Google Scholar
Cripps, A. P., and Daley, P. E. J. 1994. Two cornutes from the Middle Ordovician (Llandeilo) of Normandy, France, and a reinterpretation of Milonicystis kerfornei. Palaeontographica, Abteilung A 232:99–132.Google Scholar
Daley, P. E. J. 1992. Two new cornutes from the Lower Ordovician of Shropshire and southern France. Palaeontology 35:127–148.Google Scholar
David, B., and Mooi, R. 1999. Comprendre les échinodermes: la contribution du modèle extraxial-axial. Bulletin de la Société Géologique de France 170:91–101.Google Scholar
David, B., Lefebvre, B., Mooi, R., and Parsley, R. 2000. Are homalozoans echinoderms? An answer from the extraxial-axial theory. Paleobiology 26:529–555.Google Scholar
Domínguez, P., Jacobson, A. G., and Jefferies, R. P. S. 2002. Paired gill slits in a fossil with a calcite skeleton. Nature 417:841–844.Google Scholar
Efron, B., and Tibshirani, R. J. 1993. An introduction to the bootstrap. Chapman and Hall, New York.Google Scholar
Eble, G. J. 2000. Contrasting evolutionary flexibility in sister groups: disparity and diversity in Mesozoic atelostomate echinoids. Paleobiology 26:56–79.Google Scholar
Eble, G. J. 2004. The macroevolution of phenotypic integration. Pp. 253–273in Pigliucci, M. and Preston, K., eds. Phenotypic integration: studying the ecology and evolution of complex phenotypes. Oxford University Press, Oxford.CrossRefGoogle Scholar
Eble, G. J. 2005. Morphological modularity: empirical aspects and macroevolutionary implications. Pp. 221–238in Callebaut, W. and Rasskin-Gutman, D., eds. Modularity: understanding the development and evolution of natural complex systems. MIT Press, Cambridge.Google Scholar
Foote, M. 1991. Morphologic patterns of diversification: examples from trilobites. Palaeontology 34:461–85.Google Scholar
Foote, M. 1992. Paleozoic record of morphological diversity in blastozoan echinoderms. Proceedings of the National Academy of Sciences USA 89:7325–7329.Google Scholar
Foote, M. 1993a. Discordance and concordance between morphological and taxonomic diversity. Paleobiology 19:185–204.CrossRefGoogle Scholar
Foote, M. 1993b. Contributions of individual taxa to overall morphological disparity. Paleobiology 19:403–419.Google Scholar
Foote, M. 1994. Morphological disparity in Ordovician-Devonian crinoids and the early saturation of morphological space. Paleobiology 20:320–344.Google Scholar
Foote, M. 1995. Morphological diversification of Paleozoic crinoids. Paleobiology 21:273–299.Google Scholar
Foote, M. 1996. Models of morphological diversification. Pp. 62–86in Jablonski, D., Erwin, D., and Lipps, J., eds. Evolutionary paleobiology. University of Chicago Press, Chicago.Google Scholar
Foote, M. 1997. The evolution of morphological diversity. Annual Review of Ecology and Systematics 28:129–152.Google Scholar
Foote, M. 1999. Morphological diversity in the evolutionary radiation of Paleozoic and post-Paleozoic crinoids. Paleobiology Memoirs No. 1. Paleobiology 25(Suppl. to No. 2):1–115.Google Scholar
Foote, M., and Gould, S. J. 1992. Cambrian and Recent morphological disparity. Science 258:1816.Google Scholar
Cid, M. D. Gil, Alonso, P. Domínguez, Pobes, E. Silvan, and Rodenas, M. Escribano 1996. Bohemiaecystis jefferiesi n.sp.; primer Cornuta para el Ordovícico español. Estudios Geologicos 52:313–326.Google Scholar
Gould, S. J. 1989. Wonderful life. Norton, New York.Google Scholar
Gould, S. J. 1991. The disparity of the Burgess Shale arthropod fauna and the limits of cladistic analysis: why we must strive to quantify morphospace. Paleobiology 17:411–423.Google Scholar
Gower, J. C. 1966. Some distance properties of latent root and vector methods used in multivariate analysis. Biometrika 53:325–338.Google Scholar
Gower, J. C. 1971. A general coefficient of similarity and some of its properties. Biometrics 27:857–871.Google Scholar
Gradstein, F. M., Ogg, J. G., Smith, A. G., Agterberg, F. P., Bleeker, W., Cooper, R. A., Davydov, V., Gibbard, P., Hinnov, L., House, M. R., Lourens, L., Luterbacher, H. P., McArthur, J., Melchin, M. J., Robb, L. J., Shergold, J., Villeneuve, M., Wardlaw, B. R., Ali, J., Brinkhuis, H., Hilgen, F. J., Hooker, J., Howarth, R. J., Knoll, A. H., Laskar, J., Monechi, S., Powell, J., Plumb, K. A., Raffi, I., Röhl, U., Sanfilippo, A., Schmitz, B., Shackleton, N. J., Shields, G. A., Strauss, H., van Dam, J., Veizer, J., van Kolfschoten, T., and Wilson, D. 2004. A geologic time scale 2004. Cambridge University Press, Cambridge.Google Scholar
Guensburg, T. E., and Sprinkle, J. 2000. Ecologic radiation of Cambro-Ordovician echinoderms. Pp. 428–444in Zhuravlev, A. Y. and Riding, R., eds. The ecology of the Cambrian radiation. Columbia University Press, New York.CrossRefGoogle Scholar
Harper, D. A. T., and Tychsen, A. 2004. The Orthida: disparity, diversity and distributional dynamics in a Palaeozoic brachiopod clade. Erlanger Geologische Abhandlungen 5:40.Google Scholar
Haude, R. 1995. Echinodermen aus dem Unter-Devon der argentinischen Präkordillere. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 197:37–86.CrossRefGoogle Scholar
Jablonski, D. 1986. Background and mass extinctions: the alternation of macroevolutionary regimes. Science 231:129–133.CrossRefGoogle ScholarPubMed
Jablonski, D. 1987. Heritability at the species level: analysis of geographic ranges of Cretaceous mollusks. Science 238:360–363.Google Scholar
Jablonski, D. 1993. The tropics as a source of evolutionary novelty through geological time. Nature 364:142–144.Google Scholar
Jablonski, D. 1998. Geographic variation in the molluscan recovery from the end-Cretaceous extinction. Science 279:1327–1330.Google Scholar
Jablonski, D., and Bottjer, D. J. 1991. Environmental patterns in the origin of higher taxa: the post-Paleozoic fossil record. Science 252:1831–1833.Google Scholar
Jaekel, O. 1901. Uber Carpoideen; eine neue Klasse von Pelmatozoen. Zeitschrift der Deutschen Geologischen Gesellschaft 52:661–677.Google Scholar
Jefferies, R. P. S. 1968. The subphylum Calcichordata (Jefferies 1967) primitive fossil chordates with echinoderm affinities. Bulletin of the British Museum (Natural History) Geology 16:243–339.Google Scholar
Jefferies, R. P. S. 1984. Locomotion, shape, ornament, and external ontogeny in some mitrate calcichordates. Journal of Vertebrate Paleontology 4:292–319.Google Scholar
Jefferies, R. P. S. 1986. The ancestry of the vertebrates. British Museum (Natural History), London.Google Scholar
Jefferies, R. P. S. 1999. Which way up were the mitrates? Flat surface up. Pp. 317in Carnevali, M. D. Candia and Bonasoro, F., eds. Echinoderm research 1998. Balkema, Rotterdam.Google Scholar
Jefferies, R. P. S., and Lewis, D. N. 1978. The English Silurian fossil Placocystites forbesianus and the ancestry of the vertebrates. Philosophical Transactions of the Royal Society of London B 282:205–323.Google Scholar
Jefferies, R. P. S., and Prokop, R. J. 1972. A new calcichordate from the Ordovician of Bohemia and its anatomy, adaptations and relationships. Biological Journal of the Linnean Society 4:69–115.Google Scholar
Jefferies, R. P. S., Lewis, M., and Donovan, S. K. 1987. Protocystites menevensis: a stem-group chordate (Cornuta) from the Middle Cambrian of South Wales. Palaeontology 30:429–484.Google Scholar
Klingenberg, C. P. 1996. Multivariate allometry. Pp. 23–49in Marcus, L. F., Corti, M., Loy, A., Naylor, G. J. P., and Slice, D. E., eds. Advances in morphometrics. Plenum, New York.Google Scholar
Kolata, D. R., and Guensburg, T. E. 1979. Diamphidiocystis, a new mitrate “carpoid” from the Cincinnatian (Upper Ordovician) Maquoketa Group in southern Illinois. Journal of Paleontology 53:1121–1135.Google Scholar
Kolata, D. R., and Jollie, M. 1982. Anomalocystitid mitrates (Stylophora-Echinodermata) from the Champlainian (Middle Ordovician) Guttenberg Formation of the Upper Mississippi Valley Region. Journal of Paleontology 56:631–653.Google Scholar
Kolata, D. R., Frest, T. J., and Mapes, R. H. 1991. The youngest carpoid: occurrence, affinities, and life mode of a Pennsylvanian (Morrowan) mitrate from Oklahoma. Journal of Paleontology 65:844–855.Google Scholar
Lee, S. B., Lefebvre, B., and Choi, D. K. 2005. Uppermost Cambrian cornutes (Echinodermata, Stylophora) from the Tae-baeksan Basin, Korea. Journal of Paleontology 79:139–151.2.0.CO;2>CrossRefGoogle Scholar
Lefebvre, B. 1999. Stylophores (cornutes, mitrates): situation au sein du phylum des échinodermes et phylogenèse. Thèse de 3ème cycle, Université Claude Bernard-Lyon 1, Villeurbanne.Google Scholar
Lefebvre, B. 2000a. Homologies in Stylophora: a test of the “calcichordate theory.” Geobios 33:359–364.Google Scholar
Lefebvre, B. 2000b. A new mitrate (Echinodermata, Stylophora) from the Tremadoc of Shropshire (England) and the origin of the Mitrocystitida. Journal of Paleontology 53:1121–1135.Google Scholar
Lefebvre, B. 2000c. Les échinodermes stylophores du Massif armoricain. Bulletin de la Société des Sciences Naturelles de l'Ouest de la France 22:101–122.Google Scholar
Lefebvre, B. 2001. Some critical comments on “ankyroids.” Geobios 34:597–627.Google Scholar
Lefebvre, B. 2003. Functional morphology of stylophoran echinoderms. Palaeontology 46:511–555.Google Scholar
Lefebvre, B., and Fatka, O. 2003. Palaeogeographical and palaeoecological aspects of the Cambro-Ordovician radiation of echinoderms in Gondwanan Africa and peri-Gondwanan Europe. Palaeogeography, Palaeoclimatology, Palaeoecology 195:73–97.Google Scholar
Lefebvre, B., and Gutiérrez-Marco, J. C. 2003. New Ordovician mitrocystitidan mitrates (Echinodermata, Stylophora) from the Central-Iberian zone (Spain). Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 227:39–61.Google Scholar
Lefebvre, B., and Vizcaïno, D. 1999. New Ordovician cornutes (Echinodermata, Stylophora) from Montagne Noire and Brittany (France) and a revision of the order Cornuta Jaekel 1901. Geobios 32:421–458.Google Scholar
Lefebvre, B., Rachebœuf, P., and David, B. 1998. Homologies in stylophoran echinoderms. Pp. 103–109in Mooi, R. and Telford, M., eds. Echinoderms: San Francisco. Balkema, Rotterdam.Google Scholar
Lefebvre, B., Eble, G., and David, B. 2003. Morphological disparity in stylophoran echinoderms. Pp. 113–117in Féral, J. P. and David, B., eds. Echinoderm research 2001. Balkema, Rotterdam.Google Scholar
Legendre, P., and Legendre, L. 1998. Numerical ecology. Elsevier, Amsterdam.Google Scholar
Marti-Mus, M. 2002. The Ordovician cornute Flabellicystis rushtoni n. gen. n. sp. (Stylophora, Echinodermata) and its phylogenetic position within the group Cornuta. Paläontologische Zeitschrift 76:99–116.Google Scholar
McGhee, G. R. Jr. 1995. Geometry of evolution in the biconvex Brachiopoda: morphological effects of mass extinction. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 197:357–382.Google Scholar
McKerrow, W. S., and Scotese, C. R., eds. 1990. Palaeozoic palaeogeography and biogeography. Geological Society of London Memoir 12:1–12.Google Scholar
Mooi, R., and David, B. 1998. Evolution within a bizarre phylum: homologies of the first echinoderm. American Zoologist 38:965–974.Google Scholar
Mooi, R., David, B., and Marchand, D. 1994. Echinoderm skeletal homologies: classical morphology meets modern phylogenetics. Pp. 87–95in David, B., Guille, A., Féral, J. P., and Roux, M., eds. Echinoderms through time. Balkema, Rotterdam.Google Scholar
Nance, R. D., Murphy, J. B., and Keppie, J. D. 2002. A cordilleran model for the evolution of Avalonia. Tectonophysics 352:11–31.Google Scholar
Navarro, N. 2003. MDA: a MATLAB-based program for morphospace-disparity analysis. Computers and Geosciences 29:655–664.Google Scholar
Nichols, D. 1972. The water-vascular system in living and fossil echinoderms. Palaeontology 15:519–538.Google Scholar
Paris, F., and Le Hérissé, A. 1992. Palaeozoic in western Brittany (outline of the Armorican geological history and geological itinerary in the Crozon Peninsula). Cahiers de Micropaléontologie, n.s. 7:5–28.Google Scholar
Parsley, R. L. 1988. Feeding and respiratory strategies in Stylophora. Pp. 347–361in Paul, C. R. C. and Smith, A. B., eds. Echinoderm phylogeny and evolutionary biology. Clarendon, Oxford.Google Scholar
Parsley, R. L. 1991. Review of selected North American mitrate stylophorans (Homalozoa: Echinodermata). Bulletins of American Paleontology 100:5–57.Google Scholar
Parsley, R. L. 1997. The echinoderm classes Stylophora and Homoiostelea: non Calcichordata. Paleontological Society Papers 3:225–248.CrossRefGoogle Scholar
Parsley, R. L. 1998. Taxonomic revision of the Stylophora. Pp. 111–117in Mooi, R. and Telford, M., eds. Echinoderms: San Francisco. Balkema, Rotterdam.Google Scholar
Peterson, K. J. 1995. A phylogenetic test of the calcichordate scenario. Lethaia 28:25–38.Google Scholar
Robardet, M., Paris, F., and Racheboeuf, P. R. 1990. Palaeogeographic evolution of southwestern Europe during Early Palaeozoic times. Pp. 411–419in McKerrow, and Scotese, 1990.Google Scholar
Ruta, M. 1997. Redescription of the Australian mitrate Victoriacystis with comments on its functional morphology. Alcheringa 21:81–101.Google Scholar
Ruta, M. 1998. An abnormal specimen of the Silurian anomalocystitid mitrate Placocystites forbesianus. Palaeontology 41:173–182.Google Scholar
Ruta, M. 1999a. A new stylophoran echinoderm, Juliaecarpus milnerorum, from the late Ordovician Upper Ktaoua Formation of Morocco. Bulletin of the Natural History Museum, London (Geology) 55:47–79.Google Scholar
Ruta, M. 1999b. A cladistic analysis of the anomalocystitid mitrates. Zoological Journal of the Linnean Society 127:345–421.Google Scholar
Ruta, M., and Bartels, C. 1998. A redescription of the anomalocystitid mitrate Rhenocystis latipedunculata from the Lower Devonian of Germany. Palaeontology 41:771–806.Google Scholar
Ruta, M., and Jell, P. A. 1999a. Protocytidium gen. nov., a new anomalocystitid mitrate from the Victorian Latest Ordovician and evolution of the Allanicytidiidae. Memoirs of the Queensland Museum 43:353–376.Google Scholar
Ruta, M., and Jell, P. A. 1999b. Adoketocarpus gen. nov., a mitrate from the Ludlovian Kilmore Siltstone and Lochkovian Humevale Formation of central Victoria. Memoirs of the Queensland Museum 43:377–398.Google Scholar
Ruta, M., and Jell, P. A. 1999c. Two new anomalocystitid mitrates from the Lower Devonian Humevale Formation of central Victoria. Memoirs of the Queensland Museum 43:399–422.Google Scholar
Ruta, M., and Jell, P. A. 1999d. A note on Victoriacystis wilkinsi (Anomalocystitida: Mitrata) from the Upper Silurian of Victoria. Memoirs of the Queensland Museum 43:423–430.Google Scholar
Ruta, M., and Jell, P. A. 1999e. Revision of Silurian and Devonian Allanicystidiidae (Anomalocystitida: Mitrata) from southeastern Australia, Tasmania and New Zealand. Memoirs of the Queensland Museum 43:431–451.Google Scholar
Ruta, M., and Theron, J. N. 1997. Two Devonian mitrates from South Africa. Palaeontology 40:201–243.Google Scholar
Scotese, C. R. 2001. Atlas of earth history, Vol. 1. Paleogeography. PALEOMAP Project, University of Texas, Arlington.Google Scholar
Scotese, C. R., and McKerrow, W. S. 1990. Revised world maps and introduction. Pp. 1–12in McKerrow, and Scotese, 1990.Google Scholar
Smith, A. B. 1988. Patterns of diversification and extinction in Early Palaeozoic echinoderms. Palaeontology 31:799–828.Google Scholar
Smith, A. B. 1994. Systematics and the fossil record. Blackwell Scientific, Oxford.Google Scholar
Smith, A. B., and Jell, P. A. 1999. A new cornute carpoid from the Upper Cambrian (Idamean) of Queensland. Memoirs of the Queensland Museum 43:341–350.Google Scholar
Sprinkle, J., and Guensburg, T. E. 2004. Crinozoan, blastozoan, echinozoan, asterozoan, and homalozoan echinoderms. Pp. 266–280in Webby, et al., 2004b.Google Scholar
Storch, P., Fatka, O., and Kraft, P. 1993. Lower Palaeozoic of the Barrandian area (Czech Republic): a review. Coloquios de Paleontología 45:163–191.Google Scholar
Sumrall, C. D. 1997. The role of fossils in the phylogenetic reconstruction of Echinodermata. Paleontological Society Papers 3:267–288.Google Scholar
Sumrall, C. D., and Sprinkle, J. 1999. Ponticulocarpus, a new cornute-grade stylophoran from the Middle Cambrian Spence Shale of Utah. Journal of Paleontology 73:886–891.Google Scholar
Ubaghs, G. 1961. Sur la nature de l'organe appelé tige ou pédoncule chez les carpoïdes Cornuta et Mitrata. Comptes Rendus des Séances de l'Académie des Sciences de Paris 253:2738–2740.Google Scholar
Ubaghs, G. 1963. Cothurnocystis Bather, Phyllocystis Thoral and an undetermined member of the order Soluta (Echinodermata, Carpoïdea) in the uppermost Cambrian of Nevada. Journal of Paleontology 37:1133–1142.Google Scholar
Ubaghs, G. 1968. Stylophora. Pp. S495–S565in Beaver, H. H., Caster, K. E., Durham, J. W., Fay, R. O., Fell, H. B., Kesling, R. V., Macurda, D. B. Jr., Moore, R. C., Ubaghs, G., and Wanner, J.Echinodermata 1. Part S ofMoore, R. C., ed. Treatise on invertebrate paleontology. Geological Society of America, New York, and University of Kansas Press, Lawrence, Kansas.Google Scholar
Ubaghs, G. 1970. Les Echinodermes “carpoïdes” de l'Ordovicien inférieur de la Montagne Noire (France). Editions du CNRS, Paris.Google Scholar
Ubaghs, G. 1979. Trois Mitrata (Echinodermata: Stylophora) nouveaux de l'Ordovicien de Tchécoslovaquie. Paläontologische Zeitschrift 53:98–119.Google Scholar
Ubaghs, G. 1981. Réflexions sur la nature et la fonction de l'appendice articulé des “carpoïdes” Stylophora (Echinodermata). Annales de Paléontologie Invertébrés 67:33–48.Google Scholar
Ubaghs, G. 1983. Echinodermata. Notes sur les échinodermes de l'Ordovicien Inférieur de la Montagne Noire (France). Pp. 33–35in Courtessole, R., Marek, L., Pillet, J., Ubaghs, G., and Vizcaïno, D., eds. Calymena, Echinodermata et Hyolitha de l'Ordovicien de la Montagne Noire (France Méridionale). Mémoire de la Société d'Etudes Scientifiques de l'Aude, Carcassonne.Google Scholar
Ubaghs, G. 1987. Echinodermes nouveaux du Cambrien moyen de la Montagne Noire (France). Annales de Paléontologie 73:1–27.Google Scholar
Ubaghs, G. 1991. Deux Stylophora (Homalozoa, Echinodermata) nouveaux pour l'Ordovicien inférieur de la Montagne Noire (France méridionale). Paläontologische Zeitschrift 65:157–171.Google Scholar
Ubaghs, G. 1994. Echinodermes nouveaux (Stylophora, Eocrinoidea) de l'Ordovicien inférieur de la Montagne Noire (France). Annales de Paléontologie 80:107–141.Google Scholar
Ubaghs, G., and Robison, R. A. 1988. Homalozoan echinoderms of the Wheeler Formation (Middle Cambrian) of Western Utah. University of Kansas Paleontological Contributions 120:1–18.Google Scholar
Valentine, J. W. 2004. On the origin of phyla. University of Chicago Press, Chicago.Google Scholar
Van Valen, L. 1974. Multivariate structural statistics in natural history. Journal of Theoretical Biology 45:235–247.Google Scholar
Verniers, J., Pharaoh, T., André, L., Debacker, T. N., De Vos, W., Everaerts, M., Herbosch, A., Samuelsson, J., Sintubin, M., and Vecoli, M. 2002. The Cambrian to mid Devonian basin development and deformation history of Eastern Avalonia, east of the Midlands microcraton: new data and a review. In Winchester, J. A., Pharaoh, T. C., and Verniers, J., eds. Palaeozoic amalgamation of central Europe. Geological Society of London Special Publication 201:47–93.Google Scholar
Wagner, P. J. 1995. Testing evolutionary constraint hypotheses with early Paleozoic gastropods. Paleobiology 21:248–272.Google Scholar
Webby, B. D., Cooper, R. A., Bergström, S. M., and Paris, F. 2004a. Stratigraphic framework and time slices. Pp. 41–47in Webby, et al. 2004b.Google Scholar
Webby, B. D., Paris, F., Droser, M. L., and Percival, I. G., eds. 2004b. The great Ordovician biodiversification event. Columbia University Press, New York.Google Scholar
Wills, M. A., Briggs, D. E. G., and Fortey, R. A. 1994. Disparity as an evolutionary index: a comparison of Cambrian and Recent arthropods. Paleobiology 20:93–130.Google Scholar
Woodger, J. H. 1945. On biological transformations. Pp. 95–120in Le Gross Clark, E. and Medawar, P. B., eds. Essays on growth and form presented to D'Arcy Wentworth Thompson. Clarendon Press, Oxford.Google Scholar
Woods, I. S., and Jefferies, R. P. S. 1992. A new stem-group chordate from the Lower Ordovician of South Wales, and the problem of locomotion in boot-shaped cornutes. Palaeontology 35:1–25.Google Scholar