Metal Gear Sahelanthropus

During the Phantom Pain incident in 1984, a progenitor model to the later Metal Gear REX was developed by XOF and the Diamond Dogs.

History
Some time in 1984, Eli stole and took command of the mecha to chase down Big Boss, but was stopped by a narrow gap in the canyon it was running in.

Information
This vehicle is currently named a prototype Metal Gear Rex as a conjecture. It was first revealed in the E3 2014 trailer, and more details were given in the E3 2015 trailer.