1. A group of marine animals that are intermediate between invertebrates and vertebrates, characterized by a notochord-like structure and gill slits; members of the phylum Hemichordata.
Usage: plural form; singular is hemichordate; zoology/biology term; also called acorn worms

Examples

• Hemichordates are considered important in evolutionary studies because they share characteristics with both invertebrates and vertebrates.
• Scientists discovered new species of hemichordates in the deep ocean trenches.
• The hemichordates' gill slits suggest a distant evolutionary relationship to fish.
• Hemichordates burrow in the seafloor sediment and feed on organic particles.
• Researchers use hemichordates to understand the evolution of chordates.