Fossils
Some representative fossils from across geological Time. Upper left to bottom right: a) Archean stromatolites from Wyoming, USA; b) Paleoproterozoic stromatolites from Gunflint Formation, Canada; c) Vendian Dickinsonia from White Sea, Russia; d) Early Cambrian Burgessia arthropod from Burgess Shale, B.C., Canada; e) Ordovician Homotelus trilobite from Iowa, USA; f) Silurian Eurypterus from Bertie Group, NY, USA; g) Devonian Bothriolepis Placoderm armoured fish from Quebec, Canada; h) Carboniferous clubmoss tree bark from Poland; i) Apateon Permian Fossil Amphibian from Germany; j) Triassic Ichthyosaur from Guizhou Province, China; k) Jurassic Cycadophyte Plant from Queensland, Australia; l) Cretaceous Tyrannosaurus rex from Hell Creek, Montana, USA; m) Eocene Messelornis Bird from Messel Pit, Germany; n) Oligocene Leptauchenia Oreodont from South Dakota, USA; o) Miocene Saber-toothed cat from Gansu Province, China. |
Fossils are the remains of prehistoric animal and plant and micro-organisms, as well as traces, tracks, impressions, etc they may have left. Only a tiny proportion of all the organisms that ever lived became fossils, and even then mostly those with hard shells, bones etc that lived in conditions favourable for preservation. So our understanding of life in past ages is very uneven.
Earlier ideas
The nature of what fossils are was naturally a mystery to a civilization such as the Judaeo-Christian West which considered the entire Earth and all Creation to be no more than 5 or 6 thousand years old. Since the 16th century or so, scholars had engaged in a bitter controversy over the origin of fossils. One group held the modern view that fossils are the remains of ancient plants and animals. The other considered that fossils were either freaks of nature or creations of the devil. During the 18th century, the theory became popular that all fossils were relics of the great flood recorded in the Bible (in the 1960s or so this idea was revived by Young Earth Creationists). It was only around the beginning of the 19th century, when the basic principles of modern geology were established, that a better understand of fossils was possible. And it was not until Darwin published his masterwork on evolution that fossils were truly understood as the traces of ancient life on Earth.
The fossil record
The information revealed to us about the history of life on planet Earth, and the totality of fossils in general, is termed "the fossil record" or sometimes (in older books) the "record of the rocks". The fossil record is one of the most important ways by which we can understand the history and succession of life. However, the fossil record is also extremely capricious, because it creates a bias in terms of organisms with hard parts, while soft-bodied animals are rarely or never preserved. Many organisms probably never produced fossils, and there are a number of phyla of organisms that are not known from fossils. Fossils can only be preserved under certain conditions, and mostly only in sedimentary rocks (although there are rare exceptions, e.g. insects in amber). Also, whereas certain environments - e.g. reefs, ocean bottoms (reduced activity of decomposers and scavengers), swamps (anaerobic conditions mean little decay), and areas with high siltation rates (e.g. river floodplain) - favour fossilization, whereas others, e.g. dry uplands, grasslands, forests, etc are very poor at producing fossils. Thus the fossil record is better for some habitats and essentially non-existent for other habitats. Other factors to consider are that older fossils are less common than recent ones (because of greater time for erosion and degradation of fossil-bearing rocks), and that there are many rocks deep within the Earth's crust that contain fossils.
The rich fossil record
For all its limitations, the fossil record has taught us much about the history of life. There are many beautiful and detailed fossil collections in museums and the homes of private collectors. Images of some of these fossils are available on-line. Eventually the Internet has the potential to become a global database with virtual reality images of representative fossils which anyone can access it (Virtual Museums). In the meantime here are a very few links of what is available at present. MAK990511
Links
Links: . Liste over museets utstilte fossiler - heaps and heaps of images - from : Paleontologisk museum. Fossils, Rocks, and Time - U.S. Geological Survey - talks about the geological study of the earth and time. Includes a number of good specimens from Norway and elsewhere. Collection sorted by Geological age and Biological classification. The Virtual Fossil Museum has an enormous collection of fossil images organized by geological time and taxonomy.
page created 11 May 1999; last modified RGP111101, edited RFVS111204
checked ATW050930
