An effect that allows you to spend mana as though it were mana of any type to cast Imperiosaur won't allow you to spend mana from a source other than a basic land to cast it.

If a triggered mana ability produces mana when a basic land is tapped for mana, that additional mana is produced by the source of the triggered mana ability, not by that basic land.

If a basic land gains a mana ability, mana produced with that ability can be spent to cast Imperiosaur.