Key to the Rodentia
           
 
 Tail exceedingly long, much longer than head and body; color dusky on back, yellowish on sides, white beneath; hind legs very long; molars with complicated crown pattern of loops and whorls (Fig. 45a); upper incisors grooved
   
 Tail shorter, never more than 1.3 times head and body length; color various, rarely as above; hind legs not elongated for jumping; molars cuspidate or with a pattern of transverse loops or alternating triangles (Fig. 45b); upper incisors not grooved (except in Reithrodontomys and Synaptomys
 
           
Artiodactyla
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Carnivora
 - 
Chiroptera
 - 
Didelphimorphia
 - 
Insectivora
 - 
Lagomorpha
 - 
Rodentia
 - 
Xenarthra
Scientific Names - Common Names