Is Regal Leosaur legal in Standard, Modern, and Commander?

Regal Leosaur is legal in: Modern, Pioneer, Legacy, Vintage, Commander, Historic.

Regal Leosaur

Q: What type of card is Regal Leosaur?

Regal Leosaur is a Creature — Dinosaur Cat. Its oracle text reads: "Mutate {1}{R/W}{R/W} (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, other creatures you control get +2/+1 until end of turn."

Creature — Dinosaur Cat

$0.11 ↗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.)