Source : Webster's Revised Unabridged Dictionary (1913)

Mastodonsaurus \Mas`to*don*sau"rus\, n. [NL., fr. E. Mastodon +
   Gr. ? a lizard.] (Paleon.)
   A large extinct genus of labyrinthodonts, found in the
   European Triassic rocks.

Labyrinthodon \Lab`y*rin"tho*don\, n. [Gr. laby`rinqos labyrinth
   + 'odoy`s, 'odo`ntos, tooth.] (Paleon.)
   A genus of very large fossil amphibians, of the Triassic
   period, having bony plates on the under side of the body. It
   is the type of the order Labyrinthodonta. Called also
   {{Mastodonsaurus}}.