[Elrond of Rivendell]

I just looked up a quote:

Grond they named it, in memory of the Hammer of the Underworld of old. Great beasts drew it, orcs surrounded it, and behind walked mountain-trolls to wield it.

So Tolkien seems to make it very clear that there were trolls AND beasts. But I don't think he gave us much more precisions about these particulars beasts.

EfR