Description Marsh shrew

marsh shrew skull (side view)

the marsh shrew largest member of genus sorex in north america, , mammalogist david nagorsen described attractive mammal . fur dark brown, , has long tail. although marsh shrew s fur uniformly dark on , abdomen, abdominal fur of populations (s. b. albiventer) on olympic peninsula may white. marsh shrew 16 cm (6.3 in) in length, including 7-centimetre (2.8 in)-long tail, , weighs 14.5–16 g (0.51–0.56 oz). hind feet, fringed coarse hairs on toes, measure 19.2 mm (0.76 in).

although in areas marsh shrew sympatric other members of genus sorex, no other large, velvety, gray-black shrew shares geographic range. size distinguishes american water shrew (sorex palustris). although marsh shrew , american water shrew (the 2 largest shrews in north america) share features, american water shrew has more dark-grey-to-black fur on back, silver-grey belly , bi-colored tail , marsh shrew s fringed hairs more distinct. american water shrew has smaller skull, without marsh shrew s characteristic curvature, , upper incisors have less-distinct medial tines. marsh shrew typically has longer snout of american water shrew, more streamlined when viewed side.

the marsh shrew s skull relatively large, , condylobasal skull length greater 19.3 mm (0.76 in). there distinctive, downward-sloping curve along snout (rostrum). dental formula incisors: 1/1; unicuspids: 5/1; premolars: 1/1; molars: 3/3. of 5 upper unicuspids third distinctly smaller fourth, , have pigmented ridge extending cingulum. there large medial tine on large upper incisor, in anterior pigmented region. reddish pigmentation of enamel, result of iron deposits, thought adaptation strengthening enamel.

there no known fossil remains. marsh shrew s karyotype somatic number 2n = 54, , fundamental number = 70.