Definition

Proper noun A major taxonomic rank in biological classification, specifically a phylum within the kingdom Animalia. It comprises exclusively marine invertebrates characterized by a unique combination of features: a calcareous endoskeleton, a water vascular system with tube feet, and (in adults) pentaradial symmetry—a body plan organized in five parts around a central axis.

Usage and Examples

• Scientific Classification:

  • The study focused on the evolutionary history of phylum Echinodermata.
  • Sea stars, brittle stars, and crinoids are all classes within phylum Echinodermata.

• Descriptive Context:

  • The unique water vascular system is a defining characteristic of phylum Echinodermata.
  • Fossil records show that phylum Echinodermata has a long and diverse history.

Advanced Usage and Notes

• The term is used almost exclusively in formal scientific, biological, and zoological contexts. In general communication, the common names for its member classes (e.g., starfish, sea urchins) are used instead.
• While adults exhibit radial symmetry, the larval stages of organisms in this phylum are bilaterally symmetrical, a key point in understanding their evolution.

Variants and Related Terms

• Echinoderm (noun): Any member of the phylum Echinodermata.
  • The tide pool was full of various echinoderms.
• Echinodermal (adjective): Of or relating to the phylum Echinodermata.
  • The researcher studied echinodermal anatomy.

Synonyms and Related Concepts

• Echinoderms: This is the direct common-name equivalent for the members of the phylum.
• Marine invertebrates: A broader category that includes phylum Echinodermata along with many other phyla like Mollusca and Arthropoda.

Key Member Classes (Illustrative, not synonyms)

• Asteroidea: The class containing sea stars (starfish).
• Echinoidea: The class containing sea urchins and sand dollars.
• Holothuroidea: The class containing sea cucumbers.
• Ophiuroidea: The class containing brittle stars and basket stars.
• Crinoidea: The class containing sea lilies and feather stars.

Noun

1. radially symmetrical marine invertebrates including e.g. starfish and sea urchins and sea cucumbers