Fossils from the early Cambrian bear a striking resemblance to the velvet worms. These fossils, known as the lobopods, were marine. They were a clade from which arthropods, tardigrades, and Onychophora arose.<ref name="Cite doi|10.1038/nature13576"></ref> They are found in the Cambrian, Ordovician (possibly), Silurian, and Pennsylvanian periods.