Looks like the remains of a giant turtle to me.
See the turtle of enormous girth
Upon his back he holds the earth.
His thought is slow but not unkind
He holds us all within his mind
Upon his back all vows are made
He knows the truth but mayn’t aid
He loves the land and loves the sea
And even loves a child like me!
That probably isn’t quite right but it is from Stephen King’s Dark Tower books.