Anatomy of amphioxus (Branchiostoma)

Amphioxus has the four defining characteristics of the phylum Chordata: a dorsal hollow nerve cord supported by a flexible notochord, pharyngeal gill slits, and a post-anal tail. Muscles are segmented as myomeres. Note the absence of jaws.

Figure ©1999 Campbell et al.;  text © 2019 by Steven M. Carr