Hapyxelor, Hapaxelor or Mussie is a lake monster from Muskrat Lake—which is located in the Whitewater Region of Renfrew County, Ontario, Canada. It was described as a carnivorous 14–24 foot long, alligator-headed creature with slender neck, two humps, one big fin and two flippers.
A. W. Peever saw an animal the size of a horse crossing the lake in 1941.
In the spring of 1968, Donald Humphreys saw a silver-green animal, 24 feet long (later revised to 14–16 feet long), at the southern end of the lake. It had a large head with one tooth and a pair of front flippers.
Sonar tracings on an Eagle Z-5000 “fish finder” portable device, taken by Michael Bradley on October 5, 1988, showed two 8- to 10-foot objects swimming side by side and heading toward the surface from a depth of 54 feet.