opossum

This little guy gave me a bit of a surprise. I was wandering around the campground at Rio Claro reserve at night with my UV light looking for scorpions and anything else that would glow under the UV. The bad thing about using just the UV light is that it doesn't illuminate much else around, so I didn't even see this opossum when I walked right past it on the top of a small shrub. All I saw was something moving down the shrub right beside. I quickly switched to my headlamp and the opossum had moved down that shrub and up to another close by. Fortunately for me (and not him), he choose a small tree and quickly got the top with nowhere to go. I had him where I wanted him! Still I could tell he was bothered by my light so I took a few okay shots and then let him be. I've searched my Neotropical Rainforest Mammals field guide, but I just can't figure out what species this is.