This is the offcial design of Optimus Prime ancestor, Sentinel Prime! In the official Tranformers 3 movie trailer, he is one of the Autobots inside the Ark that appeared at the last scene. The below images are the Hasbro Transformers Movie 3 Dark Of The Moon Leader Class Sentinel Prime, after he change into earth form, which looks like a advance firetruck.
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Transformers 3 Movie Dark Of The Moon Leader Class Sentinel Prime
Transformers 3 Movie Sentinel Prime – earth form
Transformers 3 Movie Sentinel Prime – Shield?
Transformers 3 Movie Sentinel Prime – Firetruck mode
Transformers 3 Movie Autobots Ark