Amphioxus, also known as lancelet's, are usually found buried in sand in shallow parts of temperate and tropical seas. Amphioxus is believed to be the most primitive example of vertebrate . It is believed to be the ancestral precursor for all other vertebrates. It is important in zoology and may provide indications about the origins of vertebrates. Amphioxus serve as an intriguing comparison point for tracing how vertebrates have evolved and adapted. Although Amphioxus split from vertebrates more than 520 million years ago, their genomes hold clues about evolution, particularly how vertebrates have employed old genes for new functions. Lancelets grow up to about 2.0 in long, reaching 2.8 in at the longest. They have a translucent, somewhat fish-like body, but without any paired fins or other limbs.
an amphioxus
Amphioxi spend much of their time buried in gravel or mud on the ocean bottom, although they are able to swim. When feeding, they let the anterior part of the body project from the surface of the gravel so that they can filter food particles from water passing through their gill slits. At night they often swim near the bottom. They burrow into sand using rapid movements of the body, which is tapered at both ends and is covered by a sheath (the cuticle).
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