Abstract
Clypeaster is a speciose echinoid genus with almost 50 extant and approximately 350 extinct species, encompassing a great heterogeneity of form. While some attempts to subdivide this genus have been made, none has gained widespread support, and all recent taxonomic treatments have left the genus intact. Here we report new data on internal buttress arrangement, determined from X-Ray tomography, and plate architecture, and use this to establish relationships amongst 19 extant species encompassing 8 of the 10 nominal subgenera that have been proposed. A cladistic analysis of these characters allows us to test the validity of previously suggested subgenera of Clypeaster. Our analysis confirms that Clypeaster is monophyletic with the clypeasteroid family Arachnoididae (as represented by Arachnoides and Ammotrophus) as its immediate sister-group. It also identifies Orthanthus as the most primitive subgenus in the family Clypeaster. However, none of the previously proposed subdivisions of Clypeaster were recovered as clades and test architecture proves too homoplasous to allow a confident basis on which to subdivide the genus.
References
Agassiz, A. (1863) List of the Echinoderms. Bulletin of the Museum of Comparative Zoology, Harvard, 1, 17–28.
Agassiz, A. (1869) Preliminary report on the echini and starfishes dredged in deep water between Cuba and the Florida reef. Bulletin of the Museum of Comparative Zoology, Harvard, 1, 253–308.
Bell, F.J. (1884) On the generic position and relations of Echinanthus (Anomalanthus n. g.) tumidus. Proceedings of the Zoological Society, London, 1884, 40–44, pls 2–3.
Clark, H.L. (1914) The echinoderms of the Western Australian Museum. Records of the Western Australia Museum, 1, 132–173, pls17–26.
Clark, H.L. (1938) Echinoderms from Australia. Memoirs of the Museum of Comparative Zoology, Harvard, 55, 1–597, pls 1–28.
Clark, H.L. (1941) Reports on the Scientific Results of the Atlantis Expeditions to the West Indies under the Joint Auspices of the University of Havana and Harvard University: The Echinoderms (Other Than Holothurians). Memorias de la Sociedad Cubana de Historia Natural, 15, 1–154.
de Meijere, J.C.H. (1902) Vorläufige Beschreibung der neuen, durch die Siboga-Expedition gesammelten Echiniden. Tijdschrift van de Nederlansche Dierkundige Vereeniging Leiden (2), 8, 1–16.
Desmoulins, C. (1835) Premier mémoire sur les Échinides. Prodrome d’une nouvelle classification des ces animaux. Actes de la Société Linnéenne de Bordeaux, 7, 167–245.
Döderlein, L. (1885) Seeigel von Japan und den Liu-Kiu-Inseln. Archiv der Naturgeschichte, 51, 73–112.
Durham, J.W. (1955) Classification of Clypeasteroid echinoids. University of California Publications in Geological Sciences, 31, 73–198.
Durham, J.W. (1966) Clypeasteroids. In: Moore, R.C. (Ed.) Treatise on Invertebrate Paleontology. University of Kansas and Geological Society of America Press, Boulder, Co., pp. U450–491.
Endean, R., and E.C. Pope, 1964. Rediscovery of the echinoid Clypeaster tumidus (Tenison-Woods) and an emended description. Records of the Australian Museum, 26(9), 275–281, pls 29–30.
Gray, J.E. (1825) An attempt to divide the Echinida, or sea eggs, into natural families. Annales of Philosophy, 26, 423–431.
Gray, J.E. (1851) New genera and species of Scutellidae and Echinolampidae. Proceedings of the Zoological Society London, 19, 34–38.
Hopkins, T.S. (1988) A review of the distribution and proposed morphological groupings of extant species of genus Clypeaster in the Caribbean Sea and Gulf of Mexico. In: Burke R.D. et al. (Eds) Echinoderm Biology, Balkema, Rotterdam, pp. 337–345.
Kier & Lawson (1978) Index of living and fossil Echinoids 1924–1970. Smithsonian Contributions to Paleobiology, 34, 182 pp.
Koehler, R. (1922) Echinides du musée indien à Calcutta. 11. Clypeastridés et Cassidulidés. Echinoderma of the Indian Museum, part IX, Echinoidea (II). Calcutta, 161 pp.
Kroh, A. (2010) Index of living and fossil Echinoids 1971–2008. Annalen des Naturhistorischen Museums in Wien, Serie A, 112, 195–470.
Kroh, A. & Smith, A. B. (2010). The phylogeny and classification of post-Palaeozoic echinoids. Journal of Systematic Palaeontology, 8, 147–212.
Lamarck, J.B. (1801). Système des animaux sans vertèbres, ou tableau général des classes, des ordres et des genres de ces animaux. Déterville, Paris.
Lamarck, J.B. (1816) Histoire naturelle des animaux sans vertèbres, volume 3. Echinides. Paris, pp. 1–59.
Lambert, J. (1912) Description des échinides des terrains Néogènes du bassin du Rhone. Mémoires de la Société Paléontologique Suisse, 38, 51–102, pls 4–7.
Lambert, J. (1913) Description des échinides des terrains Néogènes du bassin du Rhone. Mémoires de la Société Paléontologique Suisse, 39, 105–151, pls 8–12.
Lambert, J. & Thiéry, P. (1909–1925) Essai de nomenclature raisonnée des échinides. Chaumont, Librairie Ferrière, 607 pp.
Leske, N.G. (1778) Iacobi Theodori Klein Naturalis dispositio Echinodermatum. Leipzig, Germany.
Linnaeus, C. (1758) Systema naturae per regna tria naturae :secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Laurentii Salvii, Stockholm.
Michelin, H. (1855) Notice sur un genre nouveau a établir dans la familie des Spatangoides sous le nom de Maera. Revue et Magazine de Zoologie, 2e serie, 7, 245–248.
Mooi, R. (1989) Living and Fossil Genera of the Clypeasteroida (Echinoidea: Echinodermata): An Illustrated Key and Annotated Checklist. Smithsonian Contributions to Zoology, 488, 1–51.
Mooi, R. (1990) Paedomorphosis, Aristotle’s lantern, and the origin of the sand dollars (Echinodermata: Clypeasteroida). Paleobiology, 16, 25–48.
Mortensen, T. (1948a). New Echinoidea (Cassiduloida, Clypeasteroida): preliminary notice. Videnskabelige Meddelelser fra Dansk Naturhistorisk Forening 111, 67–72.
Mortensen, T. (1948b) A monograph of the Echinoidea. Volume 4, part 2, Clypeastroida. Copenhagen: C.A. Reitzel. 471 pp. 72 pls.
Pfeffer, G. (1881) Die Clypeasteriden des Hamburger Museums. Verhandlungen für naturwissenschaften vereins Hamburg-Altona, 5, 56–70.
Poddubiuk, R.H. (1985) Evolution and adaptation in some Caribbean Oligo-miocene Clypeasters. In: Keegan, B.F. & O’Connor, B.D.S. (Eds) Proceedings of 5th International Echinoderm Conference. Rotterdam, Balkema, pp. 75–80.
Poddubiuk, R.H. & Rose, E.P.F. (1984) Relationships between Mid-Tertiary echinoids faunas from the central Mediterranean and eastern Caribbean and their palaeobiographic significance. Annales Géolgiques des Pays Helleniques, 32, 115–128.
Pomel, A. (1887) Classification méthodique et généra des échinides vivants et fossiles. Alger, Typ. Adolphe, Jordan, 132 pp.
Rasband, W.S. (1997–2009) ImageJ, U.S. National Institutes of Health, Bethesda, Maryland, USA, http://rsb.info.nih.gov/ij/.
Rose, E.P.F. & Poddubiuk, R.H. (1987) Morphological variations in the Cenozoic echinoid Clypeaster and its ecological and stratigraphic significance. Annales de l’Institute geologique de Hongrie, 70, 463–469.
Schultz, H. (2006) Sea Urchins, a guide to worldwide shallow water species. Hemdingen: Heike & Peter Schultz Scientific Publications
Serafy, D.K. (1970) A new species of Clypeaster from the Gulf of Mexico and Caribbean and a key to the species in the tropical Northwestern Atlantic. Bulletin of Marine Science, 20, 662–677.
Serafy, D.K. (1971) A New Species of Clypeaster (Echinodermata, Echinoidea) from San Felix Island, with a Key to the Recent Species of the Eastern Pacific Ocean. Pacific science, 25, 165–170.
Smith, A.B. (1981) Implications of lantern morphology for the phylogeny of post-Palaeozoic echinoids. Palaeontology, 24, 779–801.
Smith, A.B. (2005) The Echinoid Directory. World Wide Web electronic publication. http://www.nhm.ac.uk/research-curation/projects/echinoid-directory/index [06.07.2010].
Swofford, D.L. (2002) PAUP*. Phylogenetic Analysis Using Parsimony (*and Other Methods). Version 4. Sinauer Associates, Sunderland, Massachusetts.