Massive Halo 4 Land Vehicle

Sorry if this is old or already found (I tried to search but it said the forum search function was down), I just noticed it during my second watch through of the “Commissioning” trailer. Anyways, here’s what I’m referring to:

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So any word on what this new huge vehicle is? I’m not sure if the picture does it justice, but it’s definitely bigger than the Elephant from Halo 3.