In marmota the baculum is greatly enlarged at the posterior end and forms a shieldlike surface.
"Genera and Subgenera of Chipmunks"
John A. White
marmota flaviventris luteola A. H. Howell.
"Mammals of the Grand Mesa, Colorado"
Sydney Anderson
marmota monax ochracea Swarth Woodchuck marmota ochracea Swarth, Univ.
"Mammals taken Along the Alaska Highway"
Rollin H. Baker