() means the defenition of the creature's name
after that is the time period said animal lived in
15. Anomalocaris (Abnormal Shrimp) Middle Cambrian
14. Eurypterids (broad wing) Middle Ordovician-Late Permian
13. Megalania (Ancient Great Roamer) Pleistocene
12. Gigantopithecus (Giant Ape) Pleistocene
11, Mosasaurus (Lizard of the Meuse River) Late Cretaceous
10, Helicoprion (Spiral Saw) Early Permian-Early Triassic
9, Titanoboa (Titanic Boa) Middle Paleocene
8, Megalodon (Big Tooth) Early Miocene to Pliocene
7, Dunkleosteus (Dunkel's Bone) Late Devonian
6, Quetzalcoatlus (Quetzalcoatl is an Aztec god, it is also where this name is from) Late Cretaceous
5, Megatherium (Great Beast) Pleistocene
4, Ophiacodon (Snake Tooth) Late Carboniferous-Early Permian
3, Spinosaurus (Spine Lizard) Late Cretaceous
2, Sarcosuchus (Flesh Crocodile) Early Cretaceous
1, Titanis (titans of greek myth is the origin of the name) Pliocene-Early Pleistocene