Definition

1. Noun:
   • A taxonomic class of marine animals: "Class Echinoidea" is the scientific classification for a group of echinoderms commonly known as sea urchins and sand dollars. These animals are characterized by a globular or flattened, rigid body covered with movable spines.

Usage Examples

• Noun:
  • The Class Echinoidea includes both spherical sea urchins and flattened sand dollars.
  • Biologists study the evolution of skeletal structure within the Class Echinoidea.

Advanced Usage

• In taxonomic hierarchy: Used in formal biological and zoological contexts to denote this specific class within the phylum Echinodermata.
  • The fossil record shows that Class Echinoidea has existed since the Ordovician period.

Variants and Related Words

• Echinoidea (noun): The same term without "class"; often used interchangeably in scientific literature.
  • Research on Echinoidea focuses on their unique water vascular system.
• Echinoid (noun/adjective): A member of the Class Echinoidea; relating to this class.
  • The beach was littered with echinoid tests (shells).
• Sea urchin (noun): A common name for many members of this class with a spherical shape.
• Sand dollar (noun): A common name for members of this class with a flattened, disc-like shape.

Synonyms

• Sea urchins and sand dollars (common name grouping).
• Echinoids (scientific/common term for members of the class).

Related Phrases

• Echinoderm class: A broader phrase indicating its phylum-level grouping.
  • Class Echinoidea is one of the five extant classes of echinoderms.

Noun

1. sea urchins and sand dollars