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Dunkleosteus terrelli - Skull elements Fish Devonian Cleveland Shale - Cleveland, Ohio, USA Very Large 790mm (31 inch) slab with partial skull This is from James Boyle Ph.D a clinical assistant professor specializing in the study of placoderms. He noted: “Yes, it's most like a Dunkleosteus based on what I can see. You have both anterior dorsal lateral plates of the thoracic armor there. These are the bones that connected with a mobile joint the head and shoulder regions of the armor. The bone to the bottom left is the internal view of the left anterior dorsal lateral plate. The bone under it is the right anterior dorsal lateral plate in external view. The piece that's skewed to the right a bit in the image is part of the left anterior dorsal lateral plate as well. The easiest way to identify which of the two plates is the external (from the outside) view is that there's a sensory line canal on the one plate (it's straight nearly straight line tracing across the one bone at the top). These are the lateral line system you can still see in some modern fishes and act as pressure sensors to detect movement in the water around the organism. They are only found on the outside of the body. That oblong bone at the top is probably a piece of the paranuchal plate, but if that's the case it's only a very small fraction of it. I've attached a file with your image rotated a bit and some other images to compare against for Dunkleosteus.” I have contacted and heard back from Dr. Zerina Johnson of the natural history museum, UK who specializes in and published research papers on Devonian placoderms that the partial skull is indeed from Dunkleosteus terrelli Johanson Z (null) Vertebrate cranial evolution: Contributions and conflict from the fossil record. Evolution & Development, doi: 10.1111/ede.12422 Lebedev OA, Johanson Z, Kuznetsov AN, Tsessarsky A, Trinajstic K, Isakhodzayev FB (null) Feeding in the Devonian antiarch placoderm fishes: a study based upon morphofunctional analysis of jaws. Journal of Paleontology, 1 - 18. doi: 10.1017/jpa.2022.54 Charest F, Johanson Z, Cloutier R (2022) The preorbital depression and recess of antiarch placoderms (jawed stem-gnathostomes) revisited from an ontogenetic (saltatory) point of view. Journal of Vertebrate Paleontology, 42 (1) : doi: 10.1080/02724634.2022.2116335 Johanson Z (2021) Paleontology: There are more placoderms in the sea. Current Biology, 31 (16) : R1012 - R1014. doi: 10.1016/j.cub.2021.06.073 van Mesdag SNK, den Blaauwen J, Dean MN, Johanson Z (2020) Hyperossification in the vertebral column of Devonian placoderm fishes (Arthrodira). Journal of Vertebrate Paleontology, 40(1) : e1766477 - e1766477. doi: 10.1080/02724634.2020.1766477