Urochordata

Part of speech: noun

Definitions

1. A diverse group of marine invertebrates known for possessing a notochord during their larval stage and often having a sac-like body in adulthood
2. An aquatic phylum that includes tunicates, characterized by a simple body structure and filter-feeding mechanisms as adults
3. An animal group that features members with a spinal cord-like structure in early development, typically evolving into a sessile form as adults

Etymology: Urochordata is a scientific coinage, not an ancient word, and its parts are plain Greek. "Oura" means "tail" and "chorde" means "cord" or "string," so the name refers to the notochord, a flexible rod that runs along the tail of the larval form. Only the tadpole-like larvae of these animals have that tail, and it is the feature that gave the group its name. The term was formed in modern Latin, the scientific language of classification, on the same pattern as "Chordata," the larger phylum to which these animals belong. Chordates share a notochord at some stage of life, and the urochordates, commonly called tunicates or sea squirts, keep it only in the larva before it is lost in the adult. The adults are filter feeders that sit fixed to rocks or floats, enclosed in a tough outer covering the group takes its other common name from.