Really odd fossil... I too would be interested in finding out what this is. Though I agree with @frankh8147 in that the piece looks a lot like bone and the flat surface kind of reminds me of a plesiosaur vertebra as well, I think the inner vacuities of the fossil are too big and too linearly aligned to truly represent the inner texture of a plesiosaur bone. Below images show two halved plesiosaurid vertebrae for comparison. Seeing as the irregular overall shape of the fossil and the long, channe