| A | B |
|---|
| paleontology | study of fossils and dinosaurs. |
| William Smith | discovered rocks form layers (strata) |
| Precambrian Era | earliest time in earth's history |
| Paleozoic Era | "ancient life" many shelled sea animals |
| Mesozoic Era | "middle life" dinosaurs ruled the land and sea reptiles ruled the oceans |
| Cenozoic Era | "new life" age of mammals |
| Number of Eras in Geologic Time | 4 |
| Saurischians | lizard-hipped dinosaurs |
| Ornithischians | bird-hipped dinosaurs |
| Number of fossils identified | over 250,000 |
| body fossils | actual parts of ancient animals or plants, like teeth or shells |
| molds | hollowed out space in exact shape of plant or animal |
| casts | created when molds fill up with sediment like mud |
| prints | impressions formed in mud, like dinosaur footprints or leaf imprints |
| invertebrate fossils | form from animals with no backbone that are extinct |
| vertebrate fossils | form from animals with backbones such as fish |
| plant fossils | form from plants, such as trees or ferns |
| trace fossils | are impressions left behind by plants and animals such as footprints or trails |
| dinosaurs | large group of extinct animals that lived about 220-65 million years ago |
| extinct | no longer living |
