Key to Lower Jaws in Owl Pellets in the Pacific Northwest
A. / Relatively large (and uncommon), length from back to tip of incisors over 35 mm, no coronoid process, angle of jaw rounded, (Fig. 7), cheek tooth row about 10 mm / SylvilagusfloridanusB. / Jaw smaller, under 35 mm in length, coronoid process present (but small in some), cheek tooth row less that 8 mm. / Go to 2.
A. / With a distinct gap, diasthema, between a single large, curved incisor tooth and 3 or 4 cheek teeth (Fig. 8) / Go to 3.
B. / Without a large gap between teeth, first incisor not greatly larger that other teeth or, if larger, not an arc (Fig. 9). / Go to 8.
A. / With three cheek teeth, tooth pattern complex. / Go to 4.
B. / With 4 cheek teeth, pattern 1 or 2 ovals (Fig. 8, 10). /
Northern Pocket Gopher
Thomomystalpoides
And related species.A. / Jaw length, including incisor, over 22 mm, about 7 mm from base of incisor to base of 1st cheek tooth / Rattussp.
B. / Jaw under 21 mm (18 without incisor), about 5 mm or less from base of incisor to 1st cheek tooth. / Go to 5.
A. / Cheek teeth flat crowned with a series of loops and triangles (Fig. 5, 6). / Go to 6.
B. / Cheek teeth either with obvious cones or with unevenly worn surface. / Go to 7.
A. / Cheek tooth row about 6 mm in length. / Microtustownsendii
B. / Cheek tooth row about 5 mm in length. / Microtusoregoni
A. / Coronoid process well developed, extending back over 1 mm; cheek tooth row about 4 mm in length; angular process broad at the back, over 3 mm wide with distinct lateral projection. / Jumping Mouse,
Zapussp.
B. / Coronoid process reduced, projecting upward rather than backward (Fig. 12). / Go to 8.
A. / Cheek tooth row length about 3.5 mm, 12-14 mm from base of incisors to rear of jaw. / Deer Mouse,
Peromyscusmaniculatus
B. / Cheek tooth row about 3 mm in length, about 11 mm from base of incisors to rear of jaw. / House Mouse,
Musmusculus
A. / Without distinctly enlarged canine teeth, (Fig. 3). / Go to 10.
B. / With distinctly enlarged canine teeth or “fangs” (Fig. 8). / Go to 14.
A. / Teeth reddish brown at tips, 1st incisor, if present, elongated with several rounded cones, nearly as long as rest of tooth row, directed forward and thus like an extension of the jaw. / Shrews, genus Sorex
Go to 11.
B. / Teeth white or gray but not reddish at tips, 1st incisor like other teeth in size. /
Moles, genus Scapanus
Go to 12.A. / Total length of lower jaw about 7 mm with 1st incisor, 1st incisor 2-3 mm in length. /
Wandering Shrew,
SorexvagransB. / Total length of lower jaw about 12-13 mm, 1st incisor 3-4 mm in length. / Pacific Water Shrew,
Sorexbendirii
A. / Total length about 14 mm, tooth row about 9 mm. / Shrew mole,
Neurotrichusgibbsii
B. / Total length over 20 mm. / Go to 13.
A. / Total length about 23 mm, tooth row about 13 mm. /
Coast Mole,
ScapanusorariusB. / Total length about 23 mm, tooth row about 17 mm. / Townsend’s Mole,
Scapanus townsendii
A. / Last cheek tooth very small, less than 50% of previous tooth, 2nd to last the largest, very elongated, about the length of the 3 preceding cheek teeth, with outer surface smooth. /