from The Century Dictionary.

  • noun A rodent mammal of the family Haplodontidæ, Haplodon rufus, inhabiting Washington and Oregon and parts of California

from the GNU version of the Collaborative International Dictionary of English.

  • noun (Zoöl.) 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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun The mountain beaver (Aplodontia rufa).

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

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


from The American Heritage® Dictionary of the English Language, 4th Edition

[Chinook šwalál, robe of sewellel skins.]

from Wiktionary, Creative Commons Attribution/Share-Alike License

From Chinook sewellel, shewellel ("mountain beaver pelt robe").


  • This extinct mammal, related to the living sewellel, is the only known horned rodent and the smallest horned mammal.

    Science Press Releases

  • The name "sewellel" was applied to the robes which they made from the skins; the animal is called "show'tl," by some Indian tribes. —

    Original journals of the Lewis and Clark Expedition, 1804-1806

  • The southern part of British Columbia contains the mule deer of western North America (_Mazama macrotis_), and a very strange rodent, the sewellel or mountain beaver (_Haplodon_), a creature distantly allied to squirrels, marmots, and beavers, but restricted in its distribution to a few parts of California, Oregon, and British

    Pioneers in Canada

  • 1 The sewellel (Haplodon rufus) belongs to a family which seems to be intermediate between those of the squirrel and the beaver.

    Original journals of the Lewis and Clark Expedition, 1804-1806


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  • The mountain beaver.

    December 2, 2007