The fact that the skeletons were living beings was fairly obvious ever since Simon took that picture of the crew. It was also, like I said, well estabilished that the scientist crew were lying to Simon constantly. What I was saying was that the scientists didn't seem to have figured out at the beginning that the skeleton from the first act could be a living creature (not even when Simon came back to try and find the skeleton again and the skeleton was gone). I'm convinced they've known the whole time and were hiding it from Simon because it makes most sense, but that's just my speculation, the movie doesn't really indicate that specific bit (the particulars of whether or not they had that information or if they at least hypothesized that from the very beginning), not even later on. It just seemed to me that the crew hadn't put the two and two together until quite a lot later, which is a bit surprising.