The Echinodermata form a distinctive phylum of exclusively marine animals. They are characterized by an extensive water vascular system, an internal skeleton composed of many plates with a meshwork structure (stereom), and pentameral symmetry.

Keywords: asteroids; crinoids; echinoids; holothuroids; ophiuroids; phylogeny; water vascular system; stereom

Figure 1.

Diagrammatic representation of the water vascular system of echinoderms (after Nichols, 1969).

Figure 2.

Skeletal morphology of a typical, regular sea urchin (after Smith, 1984).

Figure 3.

Simplified phylogenetic tree for the phylum Echinodermata (after Paul and Smith, 1984). The five living classes lie across the top of the diagram. Relationships of key early echinoderms are shown below. A–E, ambulacra A–E. Note that in Camptostroma, three ambulacral tracts radiate from the mouth, with the two lateral tracts dividing to give rise to ambulacra B + C and D + E. This is the primitive 2–1–2 arrangement of ambulacra thought to derive from the three ambulacra of the helicoplacoids.


Further Reading

Boolootian RA (ed.) (1966) Physiology of Echinodermata. New York: Wiley.

Broadhead TW and Waters JA (eds) (1980) Echinoderms: Notes for a Short Course. University of Tennessee, Department of Geological Sciences, Studies in Geology, 3.

Hyman LH (1955) The Invertebrates, vol. 4: The Echinodermata. New York: McGraw‐Hill.

Jangoux M and Lawrence JM (eds) (1982) Echinoderm Nutrition. Rotterdam: Balkema.

Nichols D (1969) The Echinoderms, 2nd edn. London: Hutchinson.

Paul CRC and Smith AB (1984) The early radiation and phylogeny of the echinoderms. Biological Reviews 59: 443–481.

Paul CRC and Smith AB (eds) (1988) Echinoderm Phylogeny and Evolutionary Biology. Oxford: Liverpool Geological Society and Oxford University Press.

Smith AB (1984) Echinoid Palaeobiology. London: George Allen & Unwin.

Contact Editor close
Submit a note to the editor about this article by filling in the form below.

* Required Field

How to Cite close
Paul, Christopher RC(Mar 2003) Echinodermata. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0001615]