Thirty-two species and subspecies of this order are now recognized, all placed in the genus <em>Procavia</em> (Storr, 1780), this name antedating <em>Hyrax</em> by three years. A fossil species, <em>Pliohyrax krnppii</em>, has been described from the Pliocene of Greece and the Isle of Samos, and <em>Archæohyrax</em>, from the Miocene of Patagonia, has been assigned to this group.