Live-oak Root Borer

Description:

Huge, freaky-looking, awesome beetle! About two inches long. Big, thick mandibles. Little horns on top of its head. Wings looked rumpled, as though they were papery instead of rigid like elytra. Antennae are distinctive. When I found it, it was under the leaf litter, pulsing its abdomen over the ground. Maybe a female starting to lay eggs? No eggs were present at the time. No hair on mandibles, as far as I could tell.

Habitat:

Woods at Sandy Creek Park. A lake was nearby. Found under leaf litter. (I noticed the leaves moving up and down very slightly and was thrilled to uncover this crazy insect!)

Notes:

Could be instead Mallodon dasytomus (Hardwood Stump Borer). They look so similar that I can't tell. Beetle experts, please lend your wisdom!