"LEVIATHAN THAT CROOKED SERPENT": Ancient Leviathan Fossils Found in Arava Valley. Archaeologists and scientists have found remains of what may have been an ancient Leviathan in the Arava Valley, not far from the Dead Sea (Hana Levi Julian, The Jewish Press). Actually its a plesiosaur (kind of an aquatic dinosaur) called Elasmosaurus, not Leviathan. Leviathan is a mythological sea dragon mentioned in the Bible (e.g., Isaiah 27:1, whence the quotation), the Ugaritic texts, etc. Any connection between the two is extremely hypothetical. For example it is possible that ancient peoples occasionally dug up plesiosaur bones and that was the origin of the worldwide dragon myths. But there is no proof of this and I am skeptical.
There's lots more on ancient dragon traditions here, here, and links.