Answer: A group of extinct marine arthropods
Notes: A new study reveals a trilobite species with an extra set of legs under its head, based on fossils from New York. Trilobites are extinct marine arthropods, meaning "three-part-body" in Latin. They appeared 521 million years ago during the Cambrian period and lived for 300 million years. Trilobites became extinct 251 million years ago due to the Permian mass extinction. Recognized by their three-lobed bodies, they had exoskeletons made of chitin. They molted to grow, and most fossils are their molts. Trilobites were the first animals to develop complex eyes and multiple limbs for movement. Fossils range from 1 cm to over 70 cm.
