Power Rangers Dino Thunder: Day of the Dino (2004)

Because the world is never out of danger, three Reefside High students must rise up to meet their destiny head-on. While on a fossil-finding field trip, Conner, Kira and Ethan fall into a sinkhole and discover powerful Dino Gems that give them each awesome super abilities. But alarming evil is afoot as this new crew is confronted by terrifying Tyranodrones, Kira's sudden disappearance and Mesogog, a reptilian rogue and his robotic wrongdoers. Once Mesogog has unleashed his diabolical Zords, the teens' teacher and mentor, Dr. Tommy Oliver, has no choice but to reignite his past as the Black Power Ranger and morph them into full-fledged Rangers ready to tame the mutant terrors.