This was a grueling project I worked on for a school art contest. I used Sculptris, Blender, and Sketchup to create, work, and detail the half of the fossil.
I then used 123D to mirror it into a full formation, creating the piece you see now. It went almost smoothly, having only minor leg detail removed, and a slightly noticeable crease in the middle.
I'd prefer if distribution be kept to a minimum, as I'd hate to find this sculpture be abused.
Feel free to download and print, however!