If you activate a manland (say Inkmoth Nexus or Mishra's Factory) and then tap the land (which is now a creature) for mana, could you use that mana to play Myr Superion?
Any mana created by any permanent which had the type "creature" when it produced the mana, and is not otherwise restricted, can cast myr superion. So yes, any land creature can be used to cast it. As could an everflowing chalice animated by tezzeret.
Myr Superion + manlands