The lancelets, also known as amphioxus, are a group of small worm-like creatures that live in shallow seas around the world. In some places there can be up to five thousand lancelets per square meter of sand! They spend most of their lives buried in the sand with their heads above the surface, filtering water using mucus to catch plankton and bacteria for food.
Lancelets are chordates with an adult body plan that includes the defining chordate characteristics: a dorsal hollow neural tube, a dorsal notochord, pharyngeal slits, segmented muscles and a post anal tail.
During the Cambrian explosion over 500 million years ago, there lived an animal, Pikaia, that looked almost identical to a living lancelet. Because lancelets living today appear so similar to this early chordate fossil, scientists study them to learn about chordate evolution and specifically vertebrate evolution.
Though the lyrics are not exactly scientifically accurate, there is a fun song written about amphioxus called “It’s a Long Way From Amphioxus.”
The fossil Pikaia from about 505 million years ago.