This is a male specimen of one of the foldingdoor 'tarantulas' of the genus Antrodiaetus. Please see existing images in the guide. Males wander in search of the females (which seldom leave their burrows) at this time of year. The fused plates on the top of the abdomen are interesting. All the males I've ever seen have had three distinct plates. The plates are relicts of a time when spiders had totally segmented bodies, including the abdomen. Thus, Antrodiaetus is a very primitive kind of spider. Neat find.