Is Cloudpiercer legal in Standard, Modern, and Commander?

Cloudpiercer is legal in: Modern, Pioneer, Legacy, Vintage, Commander, Pauper, Historic.

Cloudpiercer

Q: What type of card is Cloudpiercer?

Cloudpiercer is a Creature — Dinosaur. Its oracle text reads: "Mutate {3}{R} (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.) Reach Whenever this creature mutates, you may discard a card. If you do, draw a card."

Creature — Dinosaur

$0.09 ↗20 similarCommander, Modern

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.)