Key to genera of Cricetidae in Korea

1 Two lines of cusps on upper cheek teeth; length upper molar row <20% basal length skull............................ 2

- Upper cheek teeth even (crown series with connected prisms); length upper molar row>20% basal length skull........... 3

2 Dorsal pelage stripe absent; tail 50% of head-body length; head-body length> 150 mm ...................... Tscherskia

- Narrow dark dorsal pelage stripe present; tail 30% of head-body length; head-body length <130 mm ............. Cricetulus

3 Head-body length> 260 mm; tail vertically flattened.................................................... Ondatra

- Head-body length <200 mm; tail cylindrical................................................................ 4

4 Posterior edge hard palate pointed, reaches middle of third molar; molar unrooted in adult............................ 5

- Posterior edge hard palate blunt, reaches back of the third molar; molar rooted in adult............................... 6

5 Last cheek tooth has 3 ridges lingual side........................................................ Lasiopodomys

- Last cheek tooth has> 4 ridges lingual side........................................................... Microtus

6 Greatest length of skull <25mm; ridges absence on frontal bone; tail clearly bi-color........................... Myodes

- Greatest length of skull> 25mm; frontal bone has 2 ridges from parietal toward to nasal bone; tail dully bi-color.. Craseomys