An ungual (from Latin unguis, i.e. nail) is a highly modified distal toe bone which ends in a hoof, claw, or nail. Elephants and other ungulates have ungual phalanges, as did the sauropods and horned dinosaurs. A claw is a highly modified ungual phalanx.
As an adjective, ungual means related to nail, as in periungual (around the nail).
References
Ungual Wikipedia(Text) CC BY-SA