Mēg'a-lōn'yx or Mēg'a-lō'nyx, n.

n. [Fr. mégalonyx, from Gr. μέγας, μεγάλη, great, and ὄνυξ, claw, nail.] (Palæon.) A fossil mammal, of great size, allied to the sloth. Its bones have been found in the tertiary of the Middle United States. Dana.