[quote=Sloth]
Yet the second Mizukage had a giant clam, Kisame was basically sharks personified, and their bijuu were a giant turtle and a slug. (F'in Cloud Niggas stole our octo-bull.)Pain doesn't really represent the rain village as much as he represented the Buddhist Paths of Reincarnation and the Rinnegan itself.Kishi had to hype up dat divine dojutsu. 
[/quote]

Yes but that still doesn't prohibit ninja from summoning animals that are not native to the environment. There are no rules with summoning techniques that say a ninja has to summon animals that are like the ones in the ninja's homeland, just like how there is no universal law that says that a Konoha ninja cannot use any other element than fire.