Lancelets

Lancelets are small fish-like chordates of the order Amphoxiformes. The Amphoxiformes belongs to class Leptocardii of the subphylum Cephalochordata (cephalochordates). Cephalochordates are commonly called lancelets, and possess 5 synapomorphies, or primary characteristics, that all chordates have at some point during their larval or adulthood stages.

Cephalochordates are segmented marine animals that possess elongated bodies containing a notochord that extends the length of the body from head to tail. They are only a few centimeters in length and due to their lack of a mineralized skeleton, their presence in the fossil record is minimal. Branchiostoma lanceolatum, a species that is used as a model organism for research on the development of vertebrates, has had its mitochondrial genome sequenced. The two rRNA genes and the coding genes follow the same organizational pattern as the sea lamprey (Petromyzon marinus). These and other facts support the Environmentalist Combatant scientist's contention that Branchiostoma lanceolatum and vertebrates have a close relationship.