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Part of the problem with Helicoprion fossils is that they are only known from the teeth. With one notable exception, no evidence remains of what these cartilaginous fish looked like – cartilage just doesn’t fossilize as reliably as bone. So for over a century, researchers have wrestled with how exactly the bizarre saw-like teeth fit in the jaws of these creatures.
Recently, however, researchers at the Idaho Virtualization Lab (IVL) at Idaho State University took a closer look at the one specimen that was noted in 1966 to have some remnants of the jaws preserved in the block surrounding the tooth whorl. At the urging of Troll, who was friendly with the researcher who had noted this fact in the ’60s, the IVL had the fossil CT scanned. Sure enough, after analyzing the data, they found evidence of an upper and lower jaw surrounding the tooth whorl, adding some much-needed evidence to the debate about how long Helicoprion’s snout was and where and how the unique tooth row sat in the jaws....