Cephalochordata

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Cephalochordata
English: Lancelets; Amphioxus.
Synonyms: 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.

Introduction
Lancelets 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.

Zoology
Cephalochordata 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.

Taxonomy
Lancelets are chordates with all 5 synapomorphies, the characteristics all chordates: notochord, dorsal hollow nerve cord, endostyle, pharynx and post-anal tail.

Clades
Amphioxiformes
1 Asymmetronidae: Asymmetron.
2 Branchiostomidae:    Epigonichthys;   Branchiostoma.