It means they have nails, they carry or present nails. It is the Spanishization of the name of an animal edge called Onychophora (meaning that it carries or has nails) and that belongs to the Ecdysozoa Superfilo.
Onicophores : Class of arthropods that are characterized by having the vermiform body with head provided with two antennae and short-legged rudiment. They live in Africa, Australia, Tasmania, New Zelana and Malay Peninsula.