Dune Marauder is found in Dome 3 in North Sonora Desert. It is located in the outer ring of the dome. You can access it by going inside and under the ramp in the north east side of the dome.
It appears to be a vehicle since there is a colony drone driving it.
Despite having two cannons it only fires the right one and not the left one.
The Auto-cannon is rapid but fairly weak, dealing around 80+ damage (depends on ranged protection). It has a good accuracy and long range. The Dune Marauder moves/drives constantly in a zig-zag maneuver. Sometimes the Colony Droid that mans the turret, swings his fist in the air. That indicates that the tank is about to ram. This ram is not unlike the Support Recluse, but way more deadly. Instead of knocking you back, if you stay in place while the Dune Marauder is ramming you, it can kill you instantly.
The Colony Droid on top the tank also throws 1 to 3 Molotov Cocktails Grenades (significantly like the Incendiary Grenade but a bit different). Each Cocktail that hits you deals 500 AoE damage as well some ignite damage. For every Cocktail he throws there is an area that catches fire. Standing in it will give you an ignite debuff that is fairly weak, but is stack-able.