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| Sunday, 9 October 2005 |
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Junior Observer |  |
| News Business Features Editorial
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Fossils: Records of life preserved in stone
Fossils include the footprints of animals left in soft mud, later to be buried, and turned into stone. In some areas, herds of fossilised tracks have been found. One of the more exotic fossils is that of swimming tracks made by animals as they brush against the mud and silt floors of an ocean or lake. Under certain circumstances, fossils of animal dung, eggs, and even complete nests with eggs have been preserved in stone. Fossils are formed in a number of different ways, but most are formed when a plant or animal dies in a watery environment and is buried in mud and silt. Soft tissues quickly decompose, leaving the hard bones or shells behind. Over time, sediment builds over the top and hardens into rock. As the encased bones decay, minerals seep in, replacing the organic material cell by cell in a process called "petrification". Alternatively, the bones may completely decay, leaving a cast of the organism. The void left behind may then fill with minerals, making a stone replica of the organism. Fossils can form in unusual ways too. Small bugs or insects can become trapped in tree sap. Eventually the sap hardens and forms the semiprecious material called amber. In some pieces of amber, the entombed remains of organisms can be found. Volcanic eruptions can form fossils when animals get trapped in the hot ash flows. In this case, the fossil is a hole in the shape of the animal. By far, the most common fossil remains are those of shelled invertebrate sea loving creatures such as snails, corals, and clams.These make up most of the fossil records. Plants too can leave fossils. In fact, coal is the fossil record of whole forests; however, individual plant structures usually do not survive as the plant materials are compressed to less than one hundredth of their original size. Fossils of land animals are scarcer than those of plants. In order to become fossilised, animals must die in a watery environment and become buried in the mud and silt. Because of this requirement, most land creatures never get the chance to become fossilised unless they die next to a lake or stream. Indeed there may be whole species of land animals for which no fossil records have been discovered. We may never know how many and how diverse these animals were. **** Fossilised parts Fossilisation of skeletal structures or other hard parts is most common; only rarely are flesh and other soft parts preserved. Impressions of dinosaur skin have aided scientists in making restorations of these animals. Imprints of footprints and trails left by both vertebrate and invertebrate animals are also valuable aids to studies of prehistoric life. Coprolites are fossilised excrement material; if it is possible to determine their sources, they are useful in revealing the feeding habits of the animals. Entire animals of the late Pleistocene Ice Ages have sometimes been preserved. In Siberia some 50 specimens of woolly mammoths and a long-horned rhinoceros were found preserved in ice with even the skin and flesh intact. Several specimens of the woolly rhinoceros bearing some skin and flesh have been found in oil-saturated soils in Poland. |
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| Politics | Produced by Lake House |
Have you ever heard about fossils? Well..fossils are the record of life
preserved in monuments of stone. Almost all living organisms can leave
fossils, but only the hard parts of plants and animals usually fossilise.
Soft internal organs, muscle, and skin rapidly decay and are rarely
preserved, but the bones and shells of animals are good candidates for
fossilisation. Almost no fossil record exists for soft organisms such as
jellyfish and worms. 
