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Glossary
Amber
Fossilised plant resin, in which ancient organisms have sometimes been trapped and preserved.
Ammonites
One of the most popular fossils among collectors because they can be very beautiful, ammonites are extinct sea-dwelling molluscs of the group called cephalods; their living relatives include octopus and squid. Their hard external shells preserve well as fossils, and they are very useful in dating rocks because they evolved rapidly and individual species were only around for a short time before dying out and being replaced by another ammonite species. The shape of ammonites meant that in folklore they were thought to be the remains of coiled snakes.
Chalk
Chalk is a sedimentary rock consisting largely of the fossil remains of tiny plants that lived in ancient seas. It is a form of limestone.
Coelacanth
Often referred to as a 'living fossil', the coelacanth is a large fish that appears as a fossil since the Devonian period (see Timeline). Thought to have become extinct in the Cretaceous period, a living one was caught by a fisherman in 1938. Others have since been discovered in deep ocean waters.
Dendrites
See False fossils.
Devil's toenail
Fossil of the bivalve Gryphaea, the appearance of which gave it the folkname of 'Devil's toenail'.
Ecosystem
The term used to describe the system of interrelationships between organisms and their physical environment. It can be used to describe a specific local ecosystem or that of the planet as a whole.
False fossils
Some rocks contain features that can look very much like fossils but aren't. Flint, for example, often forms in 'nodes' that can take the shape of living organisms. The mineral manganese also forms plant-like patterns called dendrites when it seeps into certain kinds of rock.
Folklore
Fossils have been thought to be many different things in folklore. The fossil shells of belemnites (an extinct squid-like creature), for example, were believed to be thunderbolts hurled down to the Earth by the gods; while the tusks of mammoths were identified as unicorn horns. See also Devil's toenail, toadstones and snakestones.
Fossil
The word fossil comes from the Latin fossilis, meaning 'to be dug up', and it originally referred to anything buried. Now it is usually used only to describe the preserved remains of prehistoric organisms.
Fossil fuels
Oil and coal are known as fossil fuels because they are formed under great pressure from the remains of ancient plants that lived millions of years ago.
Fossilisation
The process by which fossils form, known as fossilisation, occurs only in the right circumstances. A dead organism needs to be buried quickly, normally in sediments laid down in water. Usually it is only the hard parts of an organism (bones, shell etc) that fossilise; the soft tissue decays. Preservation may be aided by mineralisation.
Gastropods
Molluscs such as the snail, slug or limpet.
Geology
The study of the origin, history and structure of the Earth, particularly the rocks that make up the Earth's crust.
Igneous rocks
Igneous rocks, such as granite, are formed when molten magma from deep beneath the Earth's surface cools. They do not contain fossils. See also sedimentary and metamorphic rocks.
Iguanadon
One of the most successful and widespread of all dinosaurs, its fossils were first identified in the 1820s. See Iguanodon bernissartensis and Iguanodon atherfieldensis.
Limestone
Limestone is a sedimentary rock consisting mainly of the shells and bones of animals and plants that lived in ancient seas. It is often very rich in fossils. Chalk is a form of limestone.
Metamorphic rocks
Great pressures and high temperatures can change, or metamorphose, rocks. Marble, for example, is a metamorphic rock formed from limestone. See also igneous and sedimentary rocks.
Mineralisation
Many fossils are formed when parts of a decaying organism are replaced by minerals in the sediments where it died. These chemical changes are known as mineralisation. See also fossilisation.
Molluscs
Molluscs are a large group of animals with more than 120,00 living species. They include familiar animals such as slugs, snails, squids, octopuses and many shellfish such as mussels, oysters and clams. Their shells and bony parts make very common fossils and can tell us a great deal about the environment in which they lived.
Palaeobiology
A branch of palaeontology that deals with the origin, development and structure of fossil animals and plants as living organisms.
Palaeontology
The study of fossils.
Sedimentary rocks
Fossils are found primarily in sedimentary rocks, formed from particles of sediment, usually laid down in water. As great weights of sediment form, the pressure compacts and cements the deeper sediments into rock. The succession of layers in sedimentary rocks forms a geological 'timeline', and the study of fossils found in different layers makes it possible to track the development of plant and animal life over time. See also igneous and metamorphic rocks.
Sharks' teeth
A common fossil find, sharks' teeth are popular among amateur collectors.
Snakestones
The coiled shape of ammonite fossils meant that in folklore they were thought to be the remains of snakes.
Stratigraphy
The study of rock layers, or strata. The way in which successive layers of rock are laid down over time, especially in sedimentary rocks, provides us with a geological timeline of the Earth's history.
Toadstones
Believed in folklore to be the warty features on toads' heads, toadstones are actually fossil teeth of the extinct fish Lepidotes.
Trace fossils
Trace fossils preserve evidence of animal activity in ancient times, rather than the animals themselves. Examples include worm burrows, trails and footprints. Trace fossils of early hominid (human-like) footprints in east Africa proved that some of our earliest ancestors walked upright on two legs. Dinosaur tracks have also helped palaeontologists to work out how these creatures moved around and what they looked like.
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