The Plygorian mammoth was an extremely large animal.
After having been unable to play an effective game of racquetball, Julian Bashir stated in 2370 that he couldn't "hit the broadside of a Plygorian mammoth." (DS9: "Rivals")
According to StarTrek.com, the Plygorian mammoth was from a planet named Plygoria and/or from a star system where the star was named Plygoria. [1](X)