A Terrapin with very large head

I recently went out on a limb and purchased some wild caught Texas terrapins. I just received them today. When I order them the seller told me that one of the large females had a very large head. I received the terrapins today. He wasn’t kidding about the female having a large head. Her carapace is 9inches in length and very smooth, so I know she is old, but her head is 3 inches long and 2.3 inches wide. I have never seen anything like this before. Since she has only been in captivity for only a few weeks I have to assume this is a natural occurrence. If any one can help me out I would appreciate it. Thanks Jonathan Here is a link some pictures. http://albums.photopoint.com/j/AlbumIndex?u=1689978&a=13480660