Zoology · Ch 2 — Kingdom Animalia
Subphylum Cephalochordata
Subphylum Cephalochordata
Cephalochordata (Latin cephalo, head; Greek chorda, cord) are small, fish-like, coelomate marine animals found in shallow waters, where they lead a burrowing way of life. Unlike the urochordates, cephalochordates retain the notochord, the dorsal tubular nerve cord and pharyngeal gill slits throughout their entire life — making them the subphylum whose adult body plan most closely matches the generalised "typical chordate" diagram used to introduce section 2.4. …
What this figure shows. A labelled lateral internal-anatomy diagram of the lancelet Amphioxus, showing a slender, laterally-compressed, fish-like body with a rod-like notochord running its full length just beneath a dorsal nerve cord that swells slightly at the front into a cerebral vesicle. The pharynx is shown perforated by a row of pharyngeal gill slits opening into a surrounding atrium that drains via a ventral atrial pore. The buccal mouth opens at the front, and the digestive tract runs back to the anus, with paired gonads shown along the body wall — no heart, jaw …