Data from: Echinoderm phylogeny including Xyloplax, a progenetic asteroid

Dryad Package Identifier	doi:10.5061/dryad.1926    671 views
Abstract	Reconstruction of the phylogeny of the five extant classes of the phylum Echinodermata has proven difficult. Results concerning higher-level taxonomic relationships among echinoderms are sensitive to the choice of analytical parameters and methods. Moreover, the proposal of a putative sixth class based on a small, enigmatic disc-shaped echinoderm, Xyloplax, from the deep seas of the Bahamas and New Zealand in the 1980s further complicated the problem. Although clearly an echinoderm, Xyloplax did not have clear affinity among known groups. Using molecular sequence and developmental data from recently collected Xyloplax adults and embryos we show that, rather than representing an ancient, distinct lineage as implied by its status as a class, Xyloplax is simply a starfish that is closely related to the asteroid family Pterasteridae. Many members of the Pterasteridae and all Xyloplax inhabit deep and polar seas and brood young. Brooding pterasterids and Xyloplax hold their young in specialized adult chambers until the young reach an advanced juvenile stage and are released as free-living individuals. We hypothesize that the unique morphology of Xyloplax evolved via progenesis - the truncation of somatic growth at a juvenile body plan but with gonadal growth to maturity. Although the overall phylogeny of extant echinoderms remains sensitive to choice of analytical methods, the placement of Xyloplax as sister to pterasterid asteroids is unequivocal. Based on this, we argue that the proposed class and infraclass status of Xyloplax should be suppressed.
Keywords	Echinoderms, Xyloplax, Phylogeny, Asteroids, Evolution of Development,
Date Deposited	2010-08-31T17:07:21Z
Scientific Names	Ciona intestinalis Acodontaster conspicuus Allostichaster sp Amblypneustes ovum Amphipholis squamata Arbacia lixula Arbacia punctulata Archaster typicus Asterias forbesi Asterina miniata Asteronyx sp Diplodontias miliaris Astropecten articulatus Astropecten polyacanthus Brisingaster robillardi Caymanostella sp Cephalodiscus gracilis Chiridota rotifera Coscinasterias muricata Crossaster papposus Cucumaria miniata Cucumaria salma Dermasterias imbricata Diplasterias brucei Echinaster sentus Echinocardium cordatum Echinus esculentus Encope aberrans Eucidaris tribuloides Eurygonias hylacanthus Evasterias troschelii Florometra serratissima Genocidaris maculata Gorgonocephalus eucnemis Gymnocrinus richeri Harriamania planktophilus Heliaster helianthoides Henricia sp Holopneustes inflatus Holothuria leucospilota Hymenaster pellucidus Leptasterias hexactis Leptosynapta clarkii Luidia clathrata Luidia foliolata Macroptychaster accrescens Meoma ventricosa Mespilia globulus Metacrinus rotundus Odontaster validus Ophiocanops fugiens Ophiocoma echinata Ophioderma brevispinum Ophiomyxa flaccida Ophionereis reticulata Ophiopholis aculeata Ophiopsammus maculata Ophiothrix oerstedii Paracentrotus lividus Parastichopus californicus Patiriella regularis Pentacta pygmaea Perknaster fuscus Pisaster ochraceus Psammechinus miliaris Pseudarchaster pareli Pseudechinus albocinctus Pseudostichopus villosus Psychropotes longicauda Pteraster tesselatus Ptychodera flava Rathbunaster californicus Saccoglossus kowalevskii Salmaciella oligopora Salmacis belli Schizostella bifurcata Solaster stimpsonii Sphaerechinus granularis Stegnaster inflatus Stichaster australis Stomopneustes variolaris Strongylocentrotus purpuratus Temnopleurus alexandri Temnotrema sculptum Tripneustes gratilla Xyloplax janetae
Spatial Coverage	World's Oceans
Temporal Coverage	Ordovician to present

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