Confidence: It's likely to be this, but I can't be certain.
Notes: Several of these were found alive inside a plastic gallon jar discarded in sand dunes, there were many dead beetles in there. This was attracting more and more to investigate the jar but they coulndnt escape once in. Some of the live ones appeared to be weak and struggling from a lengthy imprisonment. The insect doesnt look as shiny and black as it should be due to its having dwelt in decaying matter for some time.