D-Rex

D-Rex (so called because its top looks like a T-Rex skull) is the boss of the third section of Sigma's fortress in Mega Man X. Its top and bottom separate, and both try to crush and seriously damage X. When either section collides with a wall, it can daze X and knock him off. Both sections can also charge up massive electron spheres that hurtle at X to do devastating damage. Its main weakness is the Boomerang Cutter.

D-Rex (Command Mission)
In Mega Man X: Command Mission, the D-Rex is a common, but powerful, enemy that appears in the Vanallia Desert. This D-Rex is a brownish-grey and is more dinosaur-like in appearance. D-Rex attacks with shots, Heterostorm and releases explosive miniatures called Mini Rex. If its mouth is damaged, it will be unable to release miniatures.

D-Shark
D-Shark is a weaker and more colorful version of D-Rex found at the Tianna Camp. D-Shark attacks with Ultra Blizzard and releases explosive miniatures.

A D-Shark is available from the beginning in the Deployment Center.