Hello, all! I recently explored a new creek bed in west central Illinois (USA), and found 3 great finds. This is one of them, and I don't know what it is. Possibly some kind of plant matter? It was found on top of the sand after the water had receded. Weighs 3.9LBs and is 6.25 inches from bottom to top. The darker grayish "Groove" sections I refer to in the pictures seem to be the organism that was actually fossilized, and at the bottom, the "organism" itself measures about 2.5 inches across. Any ideas?