English: Lancelets; Amphioxus.
Synonym: Pharyngobranchii; Cirrhostomi; Amphioxidei; Acrania.
Name: from the Greek kephalé meaning head" and khordé meaning chord.
Genera: 2; 3 species.
Habitat: buried in sand in shallow parts of temperate or tropical seas.
Use: food for humans and domesticated animals.
IntroductionLancelets serve as an intriguing comparison point for tracing how vertebrates have evolved and adapted. They hold clues about evolution, particularly how vertebrates have employed old genes for new functions.
ZoologyCephalochordata are segmented marine animals that possess elongated bodies with a notochord that extends the length of the body, extending from head to tail, persisting throughout the animal's life. They are very small and have no hard parts. They have numerous gill slits, and have separate sexes. They are primitive chordates, similar to the archetypal vertebrate form.
Keys: notochord, dorsal hollow nerve cord, endostyle, pharyngeal slits.
TaxonomyLancelets are chordates with all 5 synapomorphies, the characteristics all chordates: notochord, dorsal hollow nerve cord, endostyle, pharynx and post-anal tail.
CladesAmphioxiformes1 Asymmetronidae: Asymmetron.
2
Branchiostomidae: Epigonichthys; Branchiostoma.