Fossils
Fossils are the remains of living organisms like plants and animals that are preserved in rock. There are many different types of fossils and many different ways in which remains can be preserved. Fossils may include all or part of an animal or plant. They may also be an impression or a mould that includes no remains at all. Fossils can also preserve a record of the action of a living organism, such as a burrow or footprints.
Fossils are usually preserved within layers of sedimentary rock (there can be exceptions to this such as the body casts left behind in volcanic rock at Pompeii or the remains of micro-organisms that live in cracks deep within the crust). Fossils found grouped together within the same layer of sediment must be of the same age and are referred to as an assemblage. These can give us information about what ancient eco-systems - communities of plants and animals – may have looked like.
Every fossil site tells us a bit about one part of the earth at one point in time. In order to build the whole story we have to look at lots of sites. A map of locations mentioned on this website is shown at right. Layers of fossil-filled rock can cover large areas and there may be more than one location in which a particular assemblage may be found. A great example of this are Tasmania's Permian rocks, which are very widespread, and their fossils quite easy to find.
There are many limitations in reading and understanding the fossil record. Neither all types of animals or plants nor all types of environments lend themselves to being preserved. Soft bodies, like jellyfish are only preserved under very special conditions. Mountain slopes are usually eroding away, their eco-systems unlikely to be preserved. This means that there is a bias in the fossil record - that some lifeforms and some environments are more likely to be represented than others. The knowledge that we draw from studying and understanding fossils is invaluable but it is always important that we bear this in mind.
Interpreting fossils and fossil assemblages can be a bit like trying to guess the picture shown on a 1000 piece jigsaw when you’ve only been given 10 bits. The good news is that we can always find more pieces! The fossil record is never complete; there is always more to discover and learn. Hunting for fossils is rewarding and lots of fun but if you do decide to go looking, remember to hunt responsibly. You can find some hints and tips on how to do that here.
