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Last Autumn, I took a side trip to Graf, Iowa in search of it's "elusive" cephalopods. Fortunately for me, a large piece of rock had released itself from the overhanging cliff and I proceeded to use my sledge hammer on it until broken into eight 50 lb pieces. This then was loaded into my truck without further exploration as I knew, each chunk contained maybe 50 cephalopods within it. These chunks of matrix were to provide me with a little winter entertainment while the landscape of Minnesota remained white. Two weeks ago I began splitting these boulders, looking for the treasures contained within. At the same time, @Ludwigia posted an image of belemnites , that made me think how similar his finds were to cephalopods of Graf. <img src='http://www.thefossilforum.com/uploads/gallery/album_1563/gallery_2384_1563_281093.jpg' alt='Acrocoelites (Acrocoelites) gracilis (Hehl in Zieten) ?' title='Acrocoelites (Acrocoelites) gracilis (Hehl in Zieten) ?' data-role='theImage'> After complimenting him on his finds, he asked to see my hash plates of Isorthoceras sociale. It is for this reason that I have put a trip report together. This location continues to perplex me a bit. How so many cephalopods over such a long period of time could keep collecting here. From my understanding, Graf, Iowa back in the Ordovician period was a very shallow marine environment where wave action altered how these cephalopod carcasses were deposited. Due to the wave action, many examples of one cephalopod being washed inside the shell of another cephalopod exist. This is very unique!! The septa of these creatures were thin and broke down readily in the surf, leaving space for other cephalopod shells to be deposited within. To show this better, here is a specimen that had all of it's septa dissolved, but the siphuncle still remained!!! Another picture showing the decayed cephalopod with remnants of a siphuncle yet no septa This I understand. But from my perspective, there are several odd factors that defy explanation from my limited knowledge with regard to the cephalopod deposition in Graf. The most prominent cephalopod rich rock is a bit orangish in color, as can be seen above. But there are 2 separate grey/brown zones that the specimens look completely different. First is an area where the cephalopods are flattened like pancakes. If you notice, the gastropods (circled) contain no distortion/ flattening. A mystery to me. The second darker zone contains cephalopods that are very small in comparison to the orange zone. They reach only about10 -20% of the "normal" size of Isorthocerus socialis found in the orange zone. A different species? Or a stress environment where they just didn't grow well? Obviously the matrix changed, so then should their environment have changed. An unknown mystery again for me.