Allosaurus Shepherd is a mythic Creature — Elf Shaman card from Jumpstart (JMP), collector number 28. Current market price: $50.90, TCGplayer market prices via Scryfall.
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.