Scapula, or Pelvis, or Skull. Oh, my!

On day 1 I went to my internship for 2 hours. I mainly focused on fine detail work under the microscope. In doing this I removed more dirt from the bone clump. I can see two different lines of neuro spine now, but there are a couple places where they look connected that I'm still working on cleaning. At this point I'm not sure if they're actually connected by caliche or if it's just very hard dirt. About halfway through picking at the bones one of them started to come loose so I vinaced it back into place and went to work on removing more dirt from the other side of the jacket. A little while ago I found a flat surface by the other bones that I thought might be a large rock, but this time when I continued to pick at it I realized it was a bone. I continued to clean it off with the dentil pick and found several large pores in it. At this point I had to stop for the day, but I decided to start with this weird bone the next time I came in. There are flat Dimetrodon bones, which I've seen before in the field, but I've never worked on them. One in particular that I've seen is the scapula. It's possible that could be what this is, but the rest of the things in this jacket seem to mainly be neuro spine and fin bones.

On day 2 I went in for 2 1/4 hours. I started moving the dirt that was covering the flat bone right away. Once I had moved a little more dirt I asked another one of the volunteers and David what they thought the bone was; they said it was most likely either part of a scapula or part of a pelvis, but it could also possibly be part of a skull. I continued to move dirt, because at this point there wasn't enough of the bone uncovered to get a good idea of what it might be. After moving the dirt off of it for almost the whole time I was there I asked David what he thought the bone was. He seconded my hypothesis that it's a pelvis, or at least part of one. I thought this because when I looked at the uncovered bone that was the first thing it looked like to me, but there's still more dirt to be removed before it's totally revealed. Take a look at the pictures bellow and see what you think.