文档介绍：Ichthyosaurs had a higher chance of being preserved than did terrestrial creatures because, as marine animals, they tended to live in environments less subject to erosion.
The quality of preservation is outstanding, but what is even more impressive is the number of ichthyosaur fossils containing preserved embryos.
After toiling up the Missouri all summer, the group wintered near the Mandan villages in the center of what is now North Dakata.
Lewis and Clark brought back much new information, including the knowledge that the continent was wider than originally supposed
Using only stone and wood tools, and without benefit of wheels or draft animals, the builders quarried ton upon ton of sandstone from the canyon walls, cut it into small blocks, hauled the blocks to the construction site, and fitted them together with mud mortar.
The rocks of the crust are of very different ages. Some continental rocks are over 3,000 million years old, while those of the ocean floor are less than 200 million yeas old.
Given that two-thirds of the Earth’s surface is water and that marine lives at all levels of the ocean, the total three-dimensional living space of the ocean is perhaps 100 times greater than that of land and contains more than 90 percent of all life on Earth even though the ocean has fewer distinct species.
Science involves imagination and creative thinking as we