nauplius

noun1

1. •
   A crustacean larva that has three pairs of locomotive organs (corresponding to antennules, antennae, and mandibles), a median eye, and little or no segmentation of the body.

   • It is not certain that phaseluses are trilobites and not naupliuses of crustaceans or an extinct group of arthropods that has yet to be recognized. — 1997