 Myriapida is a subphylum of arthropods containing millipedes, centipedes, and others. The group contains over 16,000 species, most of which are terrestrial. Although their name suggests they have myriad 10,000 legs, myriapods range from having up to 750 legs the millipede he look me plenipedes to having fewer than 10 legs. The fossil record of myriapods reaches back into the late Solokrion, although molecular evidence suggests a diversification in the Cambrian period, and Cambrian fossils exist which resemble myriapods. The oldest unequivocal myriapod fossil is of the millipede pneumodesm used pneumony, from the late Solokrion 428 million years ago. Pneumony is also important as the earliest known terrestrial animal. The phylogenetic classification of myriapods is still debated. The scientific study of myriapods is myriapodology, and those who study myriapods are myriapodologists.