Urochord

Part of speech: noun

Definitions

1. A marine invertebrate belonging to the phylum Chordata that typically has a sac-like body structure and exhibits both larval and adult forms, often found attached to substrates
2. A type of sea creature known for its distinctive notochord during its larval stage, which is retained in some forms as a gelatinous body and may be sessile as an adult
3. An aquatic organism from the phylum Chordata, characterized by a tunicate body that develops a notochord during its larval phase and can become a stationary adult

Etymology: "Urochord" is a compound built from two Greek-derived parts. The first, "uro-", comes from Greek "oura" (tail), and the second, "chord", comes from Greek "chorde" (cord, string). Together they name the animals whose larvae have a tail containing a notochord, the flexible rod that gives the larva its backbone-like support. The surprise lies in the adult form, which has lost that tail entirely. Urochordates, also called tunicates, start life as free-swimming tadpole-like larvae, then settle onto rocks, ships' hulls, or seabed surfaces and transform into sac-shaped creatures enclosed in a tough outer covering. The name therefore describes a stage most adults never display. Because the word is a plain technical coinage from classical roots, it was created by naturalists studying these animals rather than inherited from ancient writers, and it reflects the same scientific habit of naming organisms by their most visible anatomical feature.