geologic timeline andre By chlunand 541 BCE cambrian The Atmosphere is full of oxygen and animals develop. The earth doesn't have UV protection yet 485 BCE ordovician 443 BCE silurian 419 BCE devocian 358 BCE carboniferous 298 BCE permian 251 BCE triassic Period: 251 BCE to 201 BCE triassic Period: 201 BCE to 145 BCE jurassic Period: 145 BCE to 66 BCE cretaceous Period: 65 BCE to 2 BCE tertiary