No CrossRef data available.
Article contents
Are homalozoans echinoderms? An answer from the extraxial-axial theory
Published online by Cambridge University Press: 08 February 2016
Abstract
Homalozoans include four classes of non-pentamerous Paleozoic echinoderms: Homostelea (cinctans), Ctenocystoidea (ctenoid-bearing homalozoans), Homoiostelea (solutes), and Stylophora (cornutes and mitrates). Their atypical morphologies have historically made it difficult to relate them to other classes. Therefore, their systematic positions have been represented by two hypotheses (H): as stem taxa to echinoderms (H1) or as stem taxa to chordates (H2). These conclusions rest on previous inability to recognize synapomorphies with more crownward echinoderms, resulting in a forcing of the homalozoans down the phylogenetic tree that is more artifactual than evolutionary. The Extraxial-Axial Theory (EAT) identifies body-wall homologies, common ontogenetic patterns, and major events in bodyplan evolution. Therefore, the EAT can identify synapomorphies among even the most disparate of echinoderms. Application of the EAT undermines both H1 and H2 and strongly suggests that the bizarre asymmetry of homalozoans is a derived characteristic, and not indicative of plesiomorphic morphology for either chordates or echinoderms. Each of the four homalozoan clades and their major features are reexamined using the EAT. New findings are presented concerning homologies of thecal body wall, but we focus on stems, arms, and brachioles, which are recognized as very distinct products of independent evolutionary events. The results support a new interpretation (H3) of homalozoans as a polyphyletic assemblage that can be parsed out into other, clearly echinoderm clades. The Homoiostelea and Homostelea share the blastozoan synapomorphy of a brachiole. The enigmatic Ctenocystoidea also seem to have brachioles. The Stylophora have an arm as in crinoids. H3 is also more congruent with the known fossil record. Although they are stratigraphically early echinoderms, homalozoans are not indicative of the plesiomorphic morphology of the phylum.
- Type
- Articles
- Information
- Copyright
- Copyright © The Paleontological Society
References
Literature Cited
Ausich, W. I., and Babcock, L. E. 1998. The phylogenetic position of Echmatocrinus brachiatus, a probable octocoral from the Burgess Shale. Palaeontology 41:193–202.Google Scholar
Bather, F. A. 1913. Caradocian Cystidea from Girvan. Transactions of the Royal Society of Edinburgh 49:359–529.CrossRefGoogle Scholar
Bather, F. A. 1929. Une classe d'échinodermes sans trace de symétrie rayonnée. Association Française pour l'Avancement des Sciences:435–438.Google Scholar
Bather, F. A. 1930. A class of Echinodermata without trace of radiate symmetry. Archivio Zoologico Italiano 14:431–439.Google Scholar
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. 1967. Echinodermata. 1. Part S ofMoore, R. C., ed. Treatise on invertebrate paleontology. Geological Society of America and University of Kansas, New York.Google Scholar
Beisswenger, M. 1994. A calcichordate interpretation of the new mitrate Eumitrocystella savilli from the Ordovician of Morocco. Paläontologische Zeitschrift 68:443–462.CrossRefGoogle Scholar
Breimer, A. 1978. General morphology Recent crinoids. Pp. T9–T58in Ubaghs, et al. 1978.Google Scholar
Breimer, A., and Macurda, D. B. Jr. 1972. The phylogeny of the fissiculate blastoids. Proceedings of the Koninklijke Nederlandse Akademie van Wetenschappen 26:1–390.Google Scholar
Carnevali, M. D., and Bonasaro, F. 1999. Echinoderm research 1998. Balkema, Rotterdam.Google Scholar
Caster, K. E. 1983. A new Silurian carpoid echinoderm from Tasmania and a revision of the Allanicytidiidae. Alcheringa 7:321–335.CrossRefGoogle 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. 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
Chen, J.-Y., Huang, D.-Y., and Li, C.-W. 1999. An Early Cambrian craniate-like chordate. Nature 402:518–522.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.CrossRefGoogle Scholar
Cripps, A. P. 1991. A cladistic analysis of the cornutes stem chordates. Zoological Journal of the Linnean Society 102:333–366.CrossRefGoogle Scholar
Daley, P. E. J. 1992. Two new cornutes from the Lower Ordovician of Shropshire and Southern France. Palaeontology 25:127–148.Google Scholar
Daley, P. E. J. 1995. Anatomy, locomotion and ontogeny of the solute Castericystis vali from the Middle Cambrian of Utah. Geobios 28:585–615.CrossRefGoogle Scholar
Daley, P. E. J. 1996. The first solute which is attached as an adult: a Mid-Cambrian fossil from Utah with echinoderm and chordate affinities. Zoological Journal of the Linnean Society 117:405–440.CrossRefGoogle Scholar
David, B., and Mooi, R. 1996. Embryology supports a new theory of skeletal homologies for the phylum Echinodermata. Comptes Rendus de l'Académie des Sciences de Paris, série 3, 319:577–584.Google Scholar
David, B., and Mooi, R. 1998. Major events in the evolution of Echinoderms viewed by the light of embryology. Pp. 21–28 in Mooi, and Telford, 1998.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
Dominguez, P. 1999. The early evolution of echinoderms: the class Ctenocystoidea and its closest relatives revisited. Pp. 263–268 in Carnevali, Candia and Bonasoro, 1999.Google Scholar
Dzik, J., and Orlowski, S. 1995. Primitive ctenocystoid echinoderm from the earliest Middle Cambrian of Poland. Annales de Paléontologie 81:17–35.Google Scholar
Ettensohn, F. R. 1975. The autecology of Agassizocrinus lobatus. Journal of Paleontology 49:1044–1061.Google Scholar
Ettensohn, F. R. 1980. Paragassizocrinus: systematics, phylogeny and ecology. Journal of Paleontology 54:978–1007.Google Scholar
Fatka, O., and Kordule, V. 1985. Etoctenocystis bohemica gen. et sp. nov., new ctenocystoid from Czekoslovakia (Echinodermata, Middle Cambrian). Vestnik Ustredniho Ustavu Geologického 60:225–229.Google Scholar
Frest, T. J. 1988. Functional morphology and homologies in cornute and mitrate echinoderms. Pp. 797 in Burke, R. D., Mladenov, P. V., Lambert, P., and Parsley, R. L., eds. Echinoderm biology. Balkema, Rotterdam.Google Scholar
Friedrich, W. P. 1993. Systematik und Funktionmorphologie mittle Kambrischer Cincta (Carpoidea, Echinodermata). Beringeria 7:1–190.Google Scholar
Gee, H. 1996. Before the backbone, views on the origin of the vertebrates. Chapman & Hall, London.Google Scholar
Gil Cid, M. D., Dominguez, P. A., Silvan Pobes, E., and Escribano, R. M. 1996. Bohemiaecystis jefferiesi n. sp.; primer Cornuta para el Ordovicio español. Estudios Geologicos 52:313–326.Google Scholar
Gill, E. D., and Caster, K. E. 1960. Carpoid echinoderms from the Silurian and Devonian of Australia. Bulletins of American Paleontology 41:1–71.Google Scholar
Gislén, T. 1930. Affinities between the Echinodermata, Enteropneusta and Chordonia. Zoologiska Bidrag från Uppsala 12:199–304.Google Scholar
Guensburg, T. E., and Sprinkle, J. 1994. Revised phylogeny and functional interpretation of the Edrioasteroidea based on new taxa from the Early and Middle Ordovician of western Utah. Fieldiana (Geology) 29:1–43.Google Scholar
Guensburg, T. E., and Sprinkle, J. 1999. Origin of crinoid arms. Geological Society of America Abstracts with Programs 31:A44.Google Scholar
Heinzeller, T., and Welsch, U. 1994. Crinoidea. Pp. 9–148in Harrison, F. W. and Ruppert, E. W., eds. Microscopic anatomy of invertebrates, Vol. 14. Echinodermata. Wiley, New York.Google Scholar
Hotchkiss, F. H. C. 1993. A new Devonian ophiuroid (Echinodermata: Oegophiurida) from New York State and its bearing on the origin of ophiuroid upper arm plates. Proceedings of the Biological Society of Washington 106:63–84.Google Scholar
Jaekel, O. 1901. Uber Carpoideen: eine neue Klasse von Pelmatozoen. Zeitschrift der Deutschen Geologische Gesellschaft 52:661–677.Google Scholar
Jaekel, O. 1918. Phylogenie und System der Pelmatozoen. Paläontologische Zeitung 3:1–128.Google Scholar
Jefferies, R. P. S. 1967. Some fossil chordates with echinoderm affinities. Zoological Society of London, Symposium 20:163–208.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. 1981. In defence of the calcichordates. Zoological Journal of the Linnean Society 73:351–396.CrossRefGoogle Scholar
Jefferies, R. P. S. 1986. The ancestry of the vertebrates. British Museum (Natural History), London.Google Scholar
Jefferies, R. P. S. 1990. The solute Dendrocystoides scoticus from the Upper Ordovician of Scotland and the ancestry of chordates and echinoderms. Palaeontology 33:631–679.Google Scholar
Jefferies, R. P. S. 1991. Two types of bilateral symmetry in the Metazoa: chordate and bilateralian. Pp. 94–127in Bock, G. R. and Marsch, J., eds. Biological asymmetry and handedness (Ciba Foundation Symposium No. 62). Wiley, New York.Google Scholar
Jefferies, R. P. S. 1997b. How chordates and echinoderms separated from each other and the problem of dorso-ventral inversion. Pp. 249–266in Waters, and Maples, 1997.Google Scholar
Jefferies, R. P. S., Brown, N. A., and Daley, P. E. J. 1996. The early phylogeny of chordates and echinoderms and the origin of chordate left-right asymmetry and bilateral symmetry. Acta Zoologica (Stockholm) 77:101–122.CrossRefGoogle Scholar
Jell, P. A., Burett, C. F., and Banks, M. R. 1985. Cambrian and Ordovician echinoderms from eastern Australia. Alcheringa 9:183–208.CrossRefGoogle 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., Strimple, H. L., and Levorson, C. O. 1977. Revision of the Ordovician carpoid family Iowacystidae. Palaeontology 20:529–557.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.CrossRefGoogle Scholar
Lefebvre, B., and Vizcaino, 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.CrossRefGoogle Scholar
Lefebvre, B., Racheboeuf, P., and David, B. 1998. Homologies in stylophoran echinoderms. Pp. 103–109in Mooi, and Telford, 1998.Google Scholar
Lowe, C. J., and Wray, G. A. 1997. Radical alterations in the roles of homeobox genes during echinoderm evolution. Nature 389:718–721.CrossRefGoogle ScholarPubMed
Mooi, R., and David, B. 1997. Skeletal homologies of echinoderms. Pp. 305–335in Waters, and Maples, 1997. Geobiology of echinoderms.CrossRefGoogle Scholar
Mooi, R., and David, B. 1998. Evolution within a bizarre phylum: homologies of the first echinoderms. American Zoologist 38:965–974.CrossRefGoogle Scholar
Mooi, R., and David, B. 2000. What a new model of skeletal homologies tells us about asteroid evolution. American Zoologist (in press).CrossRefGoogle 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 (Echinoderms Dijon). Balkema, Rotterdam.Google Scholar
Nichols, D. 1960. The histology and activities of the tube-feet of Antedon bifida. Quarterly Journal of Microscopical Science 101:105–117.Google Scholar
Nichols, D. 1972. The water-vascular system in living and fossil echinoderms. Palaeontology 15:519–538.Google Scholar
Parsley, R. L. 1972. The Belemnocystitidae: solutan homeomorphs of the Anomalocystitidae. Journal of Paleontology, 46:341–347.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. 1990. Aristocystites, a recumbent diploporid (Echinodermata) from the Middle and Late Ordovician of Bohemia, CSSR. Journal of Paleontology 64:278–293.CrossRefGoogle Scholar
Parsley, R. L. 1991. Review of selected North American mitrate stylophorans (Homalozoa, Echinodermata). Bulletins of American Paleontology 100:5–54.Google Scholar
Parsley, R. L. 1997. The echinoderm classes Stylophora and Homoiostelea: non Calcichordata. Pp. 225–248in Waters, and Maples, 1997.Google Scholar
Parsley, R. L. 1998. Taxonomic revision of the Stylophora. Pp. 111–117in Mooi, and Telford, 1998.Google Scholar
Parsley, R. L. 1999. The Cincta (Homostelea) as Blastozoans. Pp. 369–375in Echinoderm Research 1998. Carnevali, Candia and Bonasoro, 1999.Google Scholar
Parsley, R. L., and Caster, K. E. 1965. North American Soluta (Carpoidea, Echinodermata). Bulletins of American Paleontology 49:109–174.Google Scholar
Parsley, R. L., and Mintz, L. W. 1975. North American Paracrinoidea: (Ordovician: Paracrinozoa, new: Echinodermata). Bulletins of American Paleontology 68:1–115.Google Scholar
Paul, C. R. C., and Smith, A. B. 1984. The early radiation and phylogeny of echinoderms. Biological Reviews 59:443–481.CrossRefGoogle Scholar
Peterson, K. J. 1995. A phylogenetic test of the calcichordate scenario. Lethaia 28:25–38.CrossRefGoogle Scholar
Philip, G. M. 1979. Carpoids: echinoderms or chordates? Biological Reviews 54:439–471.CrossRefGoogle Scholar
Raff, R. A. 1996. The shape of life: genes, development, and the evolution of animal form. University of Chicago Press, Chicago.CrossRefGoogle Scholar
Robison, R. A., and Sprinkle, J. 1969. Ctenocystoidea: a new class of primitive echinoderms. Science 166:1512–1514.CrossRefGoogle ScholarPubMed
Roux, M. 1997. Classification et ontogenèse chez les crinoïdes: une révision nécessaire de la hiérarchie des caractères. Bulletin de la Société Zoologique de France 122:371–378.Google Scholar
Rozhnov, S. V., and Jefferies, R. P. S. 1996. A new stem-chordate solute from the Middle Ordovician of Estonia. Geobios 29:91–109.CrossRefGoogle Scholar
Ruta, M. 1997. A new mitrate from the Lower Ordovician of southern France. Palaeontology 40:363–383.Google Scholar
Ruta, M. 1999. Brief review of the stylophoran debate. Evolution & Development 1:123–135.CrossRefGoogle ScholarPubMed
Sprinkle, J. 1973. Morphology and evolution of blastozoan echinoderms. Special publication, Museum of Comparative Zoology, Harvard University, Cambridge.CrossRefGoogle Scholar
Sprinkle, J. 1975. The “arms” of Caryocrinites, a rhombiferan cystoid convergent on crinoids. Journal of Paleontology 49:1062–1073.Google Scholar
Sprinkle, J. 1980. An overview of the fossil record. In Broadhead, T. W. and Waters, J. A., eds. Echinoderms: notes for a short course. Studies in Geology 3:15–26. Department of Geological Sciences, University of Tennessee, Knoxville.Google Scholar
Sprinkle, J. 1982. Palaeocystitids. In Sprinkle, J., ed. Echinoderm faunas from the Bromide Formation (Middle Ordovician) of Oklahoma. University of Kansas Paleontological Contributions 1:289–296.Google Scholar
Sprinkle, J. 1992. Radiation of Echinodermata. Pp. 375–398in Lipps, J. H. and Signor, P. W., eds. Origin and early evolution of the Metazoa. Plenum, New York.CrossRefGoogle Scholar
Sprinkle, J., and Collins, D. 1998. Revision of Echmatocrinus from the Middle Cambrian Burgess Shale of British Columbia. Lethaia 31:269–282.CrossRefGoogle Scholar
Sprinkle, J., and Guensburg, T. E. 1997. Early radiation of echinoderms. Pp. 205–224in Waters, and Maples, 1997.Google Scholar
Sprinkle, J., and Robison, R. A. 1978. Ctenocystoids. Pp. T998–T1002in Ubaghs, et al. 1978.Google Scholar
Sumrall, C. D. 1993. Thecal designs in isorophinid edrioasteroids and their taxonomic implications. Lethaia 26:289–302.CrossRefGoogle Scholar
Sumrall, C. D. 1997. The role of fossils in the phylogenetic reconstruction of Echinodermata. Pp. 267–288in Waters, and Maples, 1997.Google Scholar
Termier, H., and Termier, G. 1973. Les Echinodermes Cincta du Cambrien de la Montagne Noire (France). Geobios 6:243–265.CrossRefGoogle Scholar
Ubaghs, G. 1967a. General characters of Echinodermata. Pp. S3–S60in Beaver, et al. 1967.Google Scholar
Ubaghs, G. 1971. Diversité et spécialisation des plus anciens échinodermes que l'on connaisse. Biological Reviews 46:157–200.CrossRefGoogle Scholar
Ubaghs, G. 1975. Early Paleozoic echinoderms. Annual Review of Earth and Planetary Sciences 3:79–98.CrossRefGoogle 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. 1987. Echinodermes nouveaux du Cambrien moyen de la Montagne Noire (France). Annales de Paléontologie 73:1–27.Google Scholar
Ubaghs, G. 1999. Echinodermes nouveaux du Cambrien supérieur de la Montagne Noire (France méridionale). Geobios 31:809–829.CrossRefGoogle Scholar
Ubaghs, G., and Robison, R. A. 1985. A new homoiostelean and a new eocrinoid from the Middle Cambrian of Utah. University of Kansas Paleontological Contributions, Paper 115:1–14.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, Paper 120:1–17.Google Scholar
Ubaghs, G., Moore, R. C., Wienberg Rasmussen, H., Lane, N. G., Breimer, A., Strimple, H. L., Brower, J. C., Jeffords, R. M., Sprinkle, J., Peck, R. E., Macurda, D. B. Jr., Meyer, D. L., Roux, M., Sieverts-Doreck, H., Fay, R. O., and Robison, R. A. 1978. Echinodermata 2. Part T ofMoore, R. C., ed. Treatise on invertebrate paleontology. Geological Society of America and University of Kansas, Boulder, Colo.Google Scholar
Waters, J. A., and Maples, C. G., eds. 1997. Geobiology of echinoderms. Paleontological Society Papers No. 3.CrossRefGoogle Scholar
Whitehouse, F. W. 1941. Early Cambrian echinoderms similar to larval stages of Recent forms. Memoirs of the Queensland Museum 11:1–28.Google Scholar
Wray, G. A. 1999. Genes involved in the evolution of echinoderm morphology. Pp. 232in Carnevali, Candia and Bonasoro, 1999.Google Scholar