Is Allosaurus Shepherd legal in Standard, Modern, and Commander?

Allosaurus Shepherd is legal in: Legacy, Vintage, Commander, Historic.

What type of card is Allosaurus Shepherd?

Allosaurus Shepherd is a Creature — Elf Shaman. Its oracle text reads: "This spell can't be countered. Green spells you control can't be countered. {4}{G}{G}: Until end of turn, each Elf creature you control has base power and toughness 5/5 and becomes a Dinosaur in addition to its other creature types."