Urochordata

Urochordata is a subphylum of Chordata, comprising around 3,000 species, including the sea squirts, salps, and appendicularians. These marine animals are filter feeders with a water-filled, sac-like body structure and two tubular openings, known as siphons, through which they draw in and expel water.

Anatomy

Urochordates have a notable larval stage, which features a notochord, a dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail. All of these features are shared with other chordates, and are lost in the adult stage.

Classification

Urochordata is divided into three classes: Ascidiacea (sea squirts), Thaliacea (salps), and Appendicularia (larvaceans). These classes are defined by their unique life cycle stages and body structures.

Evolution

Urochordates are considered the closest relatives of Craniata, which includes the vertebrates. The nature of the relationship between these groups has been a subject of long-standing debate.

See also

• Chordate
• Invertebrate
• Marine biology

External links

• Urochordata at the University of California Museum of Paleontology
• World Register of Marine Species

Urochordata Resources
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