Читать книгу Dinosaurs - Douglas Palmer - Страница 15

It can be surprisingly difficult for the remains of any land-based animal to become fossilized, which is why we have relatively few dinosaur and human-related fossils. When most animals die on land, their corpses are scavenged and are often totally destroyed unless they contain large bones or other indigestible structures such as teeth. Prolonged exposure to weathering and erosion by wind and water further scatters and wears away the remaining bones. The preservation of an entire dinosaur skeleton would have required quick burial below new layers of sediment, a situation that occurs only in certain circumstances.

Caption: Bodies are food for scavengers.

Caption:

Exposed to the elements, the flesh decays.

Fossil hunters are able to spot the remains only after the sediment layers (strata) have been brought back up to the surface and re-exposed through earth movements or deep erosion. Experts have now learned to search out the right kind of strata that were originally laid down in the sort of environments occupied by dinosaurs and where their remains might have been buried. The deposits of rivers, lakes and near-shore deltas have proved good prospects, along with the deposits of more arid environments where footprints can be preserved.

Most dinosaurs are known only from incomplete and fragmentary skeletal remains. Commonly, the skull is missing, along with the hands and feet. Of the 600 or so different kinds of dinosaurs known so far, most are represented by just a single species. We have probably found only the tip of the proverbial iceberg. Even when a fossil has been found, identification is not necessarily certain as it depends on whether the most important characteristics have been preserved. Sometimes specimens of the same kind of dinosaur have been given different names because they have been found in different countries, or because different bits of the same animal have been found in different places.

Caption:

Resurrection in rock.