Discovery Science: Earth – Geological Eras – Paleozoic Era
Earth Science: Geological Eras – Paleozoic Era Our detailed fossil records only begin at around 542 million years ago, in the Paleozoic era. All major animal groups, excluding mammals and birds, evolved in this era, ending in a great extinction about 250 million years ago. The first proto-organisms with a cell-like structure appeared about 3.5 … Read more