Phu Nam Chan Forest Park has discovered more than 100 ancient fish fossils and is considered the first ancient fish fossil discovery in Thailand, and the fish fossils found as lepitothesi; it is a freshwater fish about 30–60 cm long that lived 65 million years ago and went extinct with dinosaurs. As of which, the ancient fish fossils mostly are in perfect condition. Oxygen gas is a key factor in keeping bacteria growing inaccessible to fish carcasses. The remains of the fish did not rot and were preserved in the shale as fossil remains until today.