- sessile, solitary or colonial, filter feeders
- adults bear little resemblance to other chordates:

- sessile and covered by a complex tunic
- have a pharynx with many gill slits
- lack a notochord and nerve cord

- the 'tadpole' larva possesses the distinctive chordate characters
- an endostyle secretes an iodinated mucous net that functions as a fine sieve; cilia propel it across the pharynx and eventually to the mouth; a likely evolutionary precursor to vertebrate thyroid gland

b) Cl. LARVACEA (appendicularians) ~70 spp.:

- pelagic; make amazing mucous houses to suspension feed; make several houses per day (4 - 16); can filter particles < 0.1 micron using a mucous net!
- the likely sister group of all remaining urochordates