DESCRIPTION OF THE DEUTEROSTOMATA (MACALISTER 1876)
| EUKARYA>UNIKONTA>OPISTHOKONTA>ANIMALIA>METAZOA>BILATERIA>DEUTEROSTOMATA |
| Deuterostomata (doo-teh-ro-sto-MAH-tah) is derived from two Greek roots that mean secondary [deutero (δευτερο)] and mouth [stoma (στόμα)]. The reference is to the formation of the mouth as a secondary infolding during gastrulation. The formal term, Deuterostomata was first used by Alexander MacAlister (1876). A common synonym for a taxon at the rank of superphylum is Deuterostomia (Grobben 1908). We have used the older term for this group. |
FIGURE 1. A cladogram of the phyla of the Deuterostomata (within the shaded box), which otherwise is patterned after Edgecombe et al. (2011) and Putnam et al. (2008) with two major clades: Chordata (C) and Ambulacraria (A). We have followed Bourlat et al. (2006) and Dunn et al. (2008) by including the Xenoturbellida as the basal taxon within the Ambulacraria.
| ALTERNATE VIEWS OF DEUTEROSTOME RELATIONSHIPS The morphological tradition of grouping phyla in the deuterostomes assumes that sessile and simple is primitive and that moving and complex is derived. This, to a large extent is a consequence of our bias as members of the vertebrates. Figure 3 shows the traditional view of the deuterostome relationships (e.g. Nielsen 2001 and Brusca and Brusca 2003) in which the echinoderms are the most primitive and the chordate groups monophyletic and the most derived. The analysis of Delsuc et al. (2006; Figure 4) was even more surprising in that it concluded that the cephalochordates were associated with the echinoderms. If so, the cephalochordate body plan is primitive, suggesting that the basic vertebrate plan also is primitive. Furthermore, the sessile natures of the echinoderms and tunicates are secondary simplifications. The molecular results call to question the concept of the chordate. In fact, the results of Delsuc et al. (2006) indicate that the “chordates” are paraphyletic. Later analyses by Delsuc et al. (2008) and Putnam et al. (2008) confirm a monophyletic chordate group (see Figure 5). In their analysis, Putnam et al. (2008) examined the amphioxus genome relative to whole genomes of other deuterostomes and found that the cephalochordates were not sisters to the vertebrates, but basal in the whole chordate clade. Furthermore, the echinoderm + hemichordate clade (a clade called Ambulacraria) was more complex . A summary analysis of deuterostomes employing molecular, morphological, and paleontological characters by Swalla and Smith (2008) suggests a relationship similar to that of Figure 5. |
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| FIGURE 2. A diagram of the typical development of a deuterostome gastrula in which the blastopore becomes the anus in the formation of a complete gut. Image from: YassineMrabet Creative Commons | FIGURE 3. Standard textbook cladogram of the relative positions of the deuterostomes. Note the sister relationship between cephalochordates and vertebrates (after Nielsen 2001 and Brusca and Brusca 2003). | FIGURE 4. This cladogram, which is equivocal regarding the hemichordates, suggests that the cephalochordates are sisters to the echinoderms (after Delsuc et al. 2006). | FIGURE 5. In this view, the cephalochordates are basal in the chordate line (after Delsuc et al. 2008). Note the sister relationships between the vertebrates and the tunicates as well as between the echinoderms and the hemichordates (after Putnam et al. 2008). |
| PHYLA OF THE DEUTEROSTOMATA |
- AMBULACRARIA (Peterson and Eernisse 2001)
XENOTURBELLIDA (Bourlat et al. 2003)
HEMICHORDATA (Bateson 1885)- ECHINODERMATA (Klein 1734)
- CHORDATA (Bateson 1885)
CEPHALOCHORDATA (Owen 1846)
TUNICATA (Lamarck 1816)
VERTEBRATA (Cuvier 1812)
| LITERATURE CITED Balfour, F. M. 1881. A Treatise on Comparative Embryology. Vol. 2. Cambridge University Press. Cambridge. Bateson, W. 1885. The later stages in the development of B. kowalevskii, with a suggestion as to the affinities of the Enteropneusta. Q. J. Microsc. Sci. 25(suppl): 81-122. Bourlat, S. J., C. Nielsen, A. E. Lockyer, D. T. Littlewood, and M. J. Telford. 2003. Xenoturbella is a deuterostome that eats molluscs. Nature. 424: 925-928. Bourlat S. J., T. Juliusdottir, C. J. Lowe, R. Freeman, J. Aronowicz, M. Kirschner, E. S. Lander, M. Thorndyke, H. Nakano, A. B. Kohn, A. Heyland, L. L. Moroz L. L., R. R. Copley, M. J. Telford. 2006. Deuterostome phylogeny reveals monophyletic chordates and the new phylum Xenoturbellida. Nature. 444: 85–88. Brusca, R. C. and G. J. Brusca. 2003. Invertebrates. Sinauer Associates, Inc. Sunderland, Mass. [L] Delsuc, F., H. Brinkmann, D. Chourrout, and H. Philippe. 2006. Tunicates and not cephalochordates are the closest living relatives of vertebrates. Nature. 439: 965-968. Delsuc, F., G. Tsagkogeorga, N. Lartillot, and H. Philippe. 2008. Additional molecular support for the new chordate phylogeny. Genesis. 46: 592-604. Dunn, C. W., A. Hejnol, D. Q. Matus, K. Pang, W. E. Browne, S. A. Smith, E. Seaver, G. W. Rouse, M. Obst, G. Edgecomb, M. V. Sorensen, S. H. D. Haddock, A. Schmidt-Rhaesa, A. Okusu, R. Mobjerg-Kristensen, W. C. Wheeler, M. Q. Martindale, and G. Giribet. 2008. Broad phylogenomic sampling improves resolution of the animal tree of life. Nature. 452: 745-749. Edgecombe, G. D., G. Giribet, C. W. Dunn, A. Hejnol,R. M. Kristensen, R. C. Neves, G. W. Rouse, K. Worsaae, and M. V. Sorensen. 2011. Higher-level metazoan relationships: recent progress and remaining questions. Organisms Diversity and Evolution. DOI 10.1007/s13127-011-0044-4. Grobben, K. 1908. Die systematische Einteilung des Tierreiches. Verhandlungen der kaiserlich-königlichen zoologisch-botanischen Gesellschaft in Wien. 58: 491-511. Klein, J. T. 1734. Naturlis dispositio echinodermatum. Accessit lucubratiuncula de aculeis echinorum marinorum, cum spicilegio de belemnitis. Tab. I-XXXV. Gedani. Linnaeus, C. 1758. Systema naturae per regna tria naturae. 10th edition. Laurentii Salvii. Stockholm. MacAlister, A. 1876. Animal Morphology and Systematic Zoology. Pt 1. Invertebrata. Longmans, Green, and Co. London. Nielsen, C. 2001. Animal Evolution: Interrelationships of the Living Phyla. 2nd Edition. Oxford University Press. Oxford. Owen, R. 1846. Lectures on the Comparative Anatomy and Physiology of the Vertebrate Animals, Delivered at the Royal College of Surgeons of England, in 1844 and 1846. Pt. 1 Fishes. Longman, Brown, Green, and Longmans. London. Putnam, N. H., T. Butts, D. E. K. Ferrier, R. F. Furlong, U. Hellsten, T. Kawashima, M. Robinson-Rechavi, E. Shoguchi, A. Terry, J.-K. Yu, E. Benito-Gutiérrez, I. Dubchak, J. Garcia-Fernàndez, J. J. Gibson-Brown, I. V. Grigoriev, A. C. Horton, P. J. de Jong, J. Jurka, V. V. Kapitonov, Y. Kohara, Y. Kuroki, E. Lindquist, S. Lucas, K. Osoegawa, L. A. Pennacchio, A. A. Salamov, Y. Satou, T. Sauka-Spengler, J. Schmutz, T. Shin-I, A. Toyoda, M. Bronner-Fraser, A. Fujiyama, L. Z. Holland, P. W. H. Holland, N. Satoh, and D. S. Rokhsar. 2008. The amphioxus genome and the evolution of the chordate karyotype. Nature. 453: 1064-1071. Swalla, B.J. and A.B. Smith. 2008. Deciphering deuterostome phylogeny: molecular, morphological and palaeontological perspectives. Phil. Trans. R. Society. B. 363: 1557-1568. |
| By Jack R. Holt. Last revised: 03/28/2013 |
