Prehistoric Turtlesaurus

• WOTC Official Reminder Textofficial rules
  Vigilance — Attacking doesn't cause this creature to tap.

• WWizards of the Coast2026-01-27
  Official Ruling
  To determine the total cost of a spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions (such as that of Prehistoric Turtlesaurus's first ability). The mana value of the spell remains unchanged, no matter what the total cost to cast it was.

Rulings via Scryfall