I recently went on a world (Caribbean) tour and visited every island, every room, every nook, every cranny I knew of, took notes on what I found, cleared the floor a few times and noted what returned (spawned) back in their places, etc. I compiled it into an updated database, I invite you all to check it out. This contains all the new enemies I could find, including some bosses, most if not all the permanent ones, and a few of the random ones where I saw them.
Note: This is based on observations in the various areas, there may be other enemies available that spawn on occasion, and there are certainly more random bosses than listed.
OFxs POTCO Enemy Database
Happy Hunting/Plundering Mateys!!!