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. These strange little animals feed by sticking their mouths out of the sand, drawing a stream of water into their mouths and filtering food particles from it using a snotty (mucous) food rope. This traps the particles and carries them to the gut (pharyngeal basket) - probably a similar approach to that used by the early fishes. The most significant feature of these animals is evolutionary - they are thought to be the closest living relative of the vertebrates and possibly the origin of the higher vertebrates. Pikaia, a fossil found in the mid Cambrium Burgess Shale supports this belief. Pikaia had segmented muscle blocks (myomeres) like a fish and a notochord but its shape was more that of a lancelet than a fish. In addition, lancelet development is more like that of the vertebrates (except for the echinoderms) than the invertebrates

• A notochord running the length of your body.
• A dorsal hollow nerve chord.
• Well developed segments and gut.
• No paired fins.
• Pharyngeal gill slits and arches
• 6. Eggs that develop according to a deuterostome pattern and embryos with a posterior blastopore.