They're extremely valuable because of their carapaces, which are covered with big slabs of horn, thin, brown, transparent, with white and yellow markings.
It would have been difficult to capture these valuable reptiles, because they wake up at the slightest sound, and their solid carapaces are harpoon-proof.
They unearthed a 6 meter long crocodile-like reptile, called Acherontisuchus, and a turtle, Puentemys, that had a carapace some 1 and a half meters across.