Well one of the most prominent features of sauropod dinosaurs was their long necks. Which is the one thing about which Job 40 says absolutely nothing.
Isaiah 27 talks about Leviathan as a coiling, twisting sea serpent. Apart from that, it says nothing whatsoever about what it looks like.
Psalm 74 contains a possible allusion to Leviathan as having multiple heads, like the Hydra from classical mythology. Apart from that, it says nothing whatsoever about its appearance.
Psalm 104 merely says that Leviathan frolics in the seas. Of its appearance, it says nothing. Nichts. Nada. Bupkis. Diddly squat.
When I read the descriptions of Behemoth and Leviathan in Job 40-41, all I see are generic large land animals and generic large sea creatures respectively. They seem to contain a mishmash of traits that can’t be pinned down to a single species, either living or extinct, and their descriptions are vague, leave a lot of things wide open to interpretation, and can’t be pinned down to any particular species, either extant or prehistoric. Anyone who thinks that they refer to sauropod dinosaurs or plesiosaurs being seen alive within human history is reading things into the Bible that simply are not there.