Is Trumpeting Gnarr legal in Standard, Modern, and Commander?

Trumpeting Gnarr is legal in: Modern, Pioneer, Legacy, Vintage, Commander, Historic.

Trumpeting Gnarr

Q: What type of card is Trumpeting Gnarr?

Trumpeting Gnarr is a Creature — Beast. Its oracle text reads: "Mutate {3}{G/U}{G/U} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.) Whenever this creature mutates, create a 3/3 green Beast creature token."

Creature — Beast

Mutate (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.)