In the middle is a cephalochordate, Amphioxus, also a filter feeder, but capable of free swimming.    From Wordnik.com.  [Ascidian evo-devo - The Panda's Thumb] Reference

In summary, the cephalochordate affinity of Pikaia is at best only weakly indicated by the characters visible in fossils discovered so far.    From Wordnik.com.  [Down with phyla! (episode II) - The Panda's Thumb] Reference

In the invertebrate cephalochordate Amphioxus, there is a family of very immunoglobulin like-molecules, Variable domain Chitin Binding Proteins, which are involved in innate immunity.    From Wordnik.com.  [Stuck on you, biological Velcro and the evolution of adaptive immunity - The Panda's Thumb] Reference

FGFRL1, the gene for the fifth member of the fibroblast growth factor receptor (FGFR) family, is found in all vertebrates from fish to man and in the cephalochordate amphioxus.    From Wordnik.com.  [BioMed Central - Latest articles] Reference

Ther diminishes the credibility of the cephalochordate—echinoderm link.    From Wordnik.com.  [Ascidian evo-devo - The Panda's Thumb] Reference