A peculiar gregarious burrowing rodent (Haplodon rufus), native of the coast region of the Northwestern United States. It somewhat resembles a muskrat or marmot, but has only a rudimentary tail. Its head is broad, its eyes are small and its fur is brownish above, gray beneath. It constitutes the family Haplodontidæ. Called also boomer, showt'l, and mountain beaver.

bulky nocturnal burrowing rodent of uplands of the Pacific coast of North America; the most primitive living rodent