Key to the Species of Cyprinidae

3a. (From 1b.) Anal fin located far to the rear of body; distance from anal fin origin to tip of snout (A) greater than 2.5 times distance between anal fin origin and base of caudal fin (B); posterior tip of dorsal fin falling far short of vertical from origin of anal fin.
grass carp
Ctenopharyngodon idella
 

3b. (From 1b.) Anal fin in normal position; distance from anal fin origin to tip of snout (A) less than 2.5 times distance between anal fin origin and base of caudal fin (B); posterior tip of dorsal fin reaching almost to or past vertical from origin of anal fin.
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