Lancelets (Amphioxus)

The Cephalochordates or lancelets are small (6-7cm long) fishlike marine invertebrates. They live buried up to their mouths in sand and are found along temperate and tropical coasts worldwide.

They have a cartilaginous rod (notochord) which runs almost from tip to tail and a dorsal nerve cord but no brain. Their circulatory system is surprisingly fishlike, even though they have no heart. They also have simple fins and swim using S-shaped movements.