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Ammonite Fossils

Fossils for Sale — Mon, 09 Feb 2009 11:44:50 +0000

The fossil ammonite is the classic fossil-what the man in the street thinks of when asked what fossil looks like. ammonites lived in the seas for about 140 million years, becoming extinct approximately 65 million years ago, about the same time as the dinosaurs at the end of the Cretaceous period. They first appeared during the Carboniferous period approximately 208,000,000 years ago becoming very abundant in the prehistoric seas. Ammonites belong to the group of creatures known as cephalopods, a group of creatures that today includes the ammonites closest living relatives such as the cuttlefish, octopus and squid. The only living creature that gives us a close approximation to the ammonite is the Nautilus which has very similar spiral shell structure.

The majority of ammonites have the characteristic coiled shell that is internally split into a number of small chambers. The ammonite itself lived in one of these chambers and when it grew too large for its current living chamber it formed a new one adjacent to the existing living chamber and then moved into it. This constant adding of chambers gives rise to the characteristic spiral shape of ammonites. The empty chambers were filled with gas and use to provide buoyancy in the ocean. Ammonites range in size from the quite small to the very large with large specimens commonly having shells of a metre across and weighing perhaps 100 kg. The very largest ammonites had shells with a diameter of 2.2 m.

The great thing about ammonites is as they were so prolific in the prehistoric oceans there are many many ammonite fossils to be found now. Indeed a short walk along the foreshore at Charmouth last summer produced severa,l much to my son's delight! They can also be easily found on the beaches to the west of Lyme Regis. A properly prepared ammonite can be a thing of beauty - have a look at the range shown below to see what is currently available:

272 fossil ammonite Madagascar strong fire flash
£6.40

Ammonite fossil matrix 80 90 million years California
£6.40

FOSSIL AMMONITE CLEONICEROUS fossils madagascar
£2.99

70MM POLISHED AMMONITE FROM MOROCCO SALE
£2.99

3 1st Grade Britsh Pyrite Ammonites Lower Oxford Clay
£8.99

4 UK Kosmoceras Ammonite
£7.99

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Ammonite Fossils

Fish Fossils

Fossils for Sale — Mon, 09 Feb 2009 11:16:26 +0000

Fish fossils are amongst the most popular fossils to collect. Ranging from pieces of the larger fish bones such as vertebrae, to complete skeletons or a ghostly outline of a fish in the rock, they are perennially popular with collectors and the curious. With such a wide range of types of fish fossil available, there is something for everyone from pocket money prices to the rare and consequently expensive! Have a look what we currently have on offer or come back soon when we are sure to have different items for you to check out.

If you are new to fossil collecting, you might like to check out our fossil buyer's guide to help you in your quest.

VERY DETAIL 91mm LYCOPTERA FISH FOSSIL STONE SPECIMEN
£17.12

Fossil Fish Knightia alta 109mm long RefAKN1
£44.99

BJF 15 x Fine Fossil Fish Gosiutichthys parvus USA
£74.99

TWO FOSSIL DIPLOMYSTUS FISH ON MATRIX
£15.99

A SHOAL OF FOSSIL KNIGHTIA ALTA FISH
£28.00

Large Fossil fish tooth Enchodus on matrix 65mmLEC1
£19.99

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Fish Fossils

What are fossils?

Fossils for Sale — Sun, 25 Jan 2009 22:43:21 +0000

Fossils are the preserved remains or traces of animals and occasionally plants from many millions of years ago. Preserved remains of animals that are older than approximately 10,000 years are usually considered to be fossils, though a more strict interpretation would probably require them to be a few million years old. Fossils are found in layers of sedimentary rock and can vary in size from the very very small (such as fossilised bacteria) to the very large such as the skeletons of large animals including dinosaurs. Usually fossils that are found show only a portion of the individual animal that was fossilised. Normally it is only the hard portions of an animals body that are preserved in this way, for example their bones and teeth. Soft tissues tend not to survive and so it is very rare to find any fossil record of them. It's also possible to find fossilised traces of the animal for example footprints or even fossilised faeces - yes you can even get fossilised dinosaur poo!

So how do fossils actually form? There are a number of different processes and different types of fossilisation possible. As an example consider the fossilisation of a shellfish. When the animal dies it will slowly sink to the bottom of the sea and gradually become covered with sand or silt. The animal's body decomposes or is eaten by scavengers. As time passes the shell gets covered by more and more layers of silt gradually becoming deep and deeper under the sea floor. Over a period of many tens of thousands of years the shell gradually undergoes a series of changes. The chemicals in the shell gradually become replaced by minerals (frequently things like calcite, Iron or silica) coming from water that is passing through the shell and layers of silt. This type of fossilisation is called permineralisation. This carries on over many millions of years until eventually it results in the replacement of all of the shell with the minerals. This leaves the fossil with the shape of the original animals shell but now actually entirely composed of rock. Now we have a fossil buried deep in the rock under the seabed.

So how does it eventually come to be found? Over a period of many millions of years geological changes and movements in the Earth's crust result in what was originally the seabed being pushed up until it is no longer the seabed, but new dry land. More geological changes and the further action of the wind and rain (through a process called erosion) eventually lead to the rock bearing the fossil being exposed leaving the fossil ready to be found. The very last stage in its journey back to the light may be with the help of a geologists hammer!

As previously mentioned there are a number of ways an organism can become fossilised. We have already discussed permineralisation where the original soft tissues are replaced with minerals such as silica calcite or iron pyrite. Other ways organisms can become fossilised include carbonisation, unaltered preservation, recrystallisation and authigenic preservation. In unaltered preservation the organism is preserved as it originally was because it is protected for other effects and decomposition in some way. The classic example of this is an insect that becomes trapped in tree sap which over millions of years turns to Amber, preserving the insect in its entirety. Carbonisation (sometimes also called coalification) results in everything but carbon being removed from the organism. Authigenic preservation refers to fossils of molds or casts of organisms that themselves have entirely decomposed leaving just the cast preserved in the rock. These are fossil equivalents of the worm casts that you often find on a sandy beach. Finally recrystallisation describes the process where crystals form inside the structure of the organism. These crystals eventually replace it entirely - leaving just a crystallised copy.

The different types of mineral that replacing the original organisms structure in permineralisation often result in the final fossil having a distinctive appearance. For example in the case of an ammonite when fossilised these can show considerably different appearances depending on the mineral in question. The ammonites you usually find look like the rock they come from but it is also quite common to find pyritised ammonites which show a lovely golden metallic sheen.

Hopefully this is given you an idea of how fossils come to be and what they are. Have a look through the rest of the website or some of our recommended links to find out much more!

AAA Grade OREGON CARNELIAN AGATE Slab 64g
£3.20

MASSIVE MEGALODON SHARK TOOTH 561 Fossil Teeth Ocean
£91.22

MASSIVE MEGALODON SHARK TOOTH 435 Fossil Teeth Ocean
£19.85

MASSIVE MEGALODON SHARK TOOTH 391 Fossil Teeth Ocean
£14.40

LARGE QUALITY TRICERATOPS DINOSAUR TOOTH 182
£11.49

LARGE QUALITY TRICERATOPS DINOSAUR TOOTH 183
£11.49

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What are fossils?