With a greater variety of rare fossils online on ebay, how do you know what your buying? Should you buy? Here is a little description on a few types of increasingly common fossils on ebay.
Gastrolith – Also called a stomach stone or gizzard stone. A gastrolith is a rock held inside a gastrointestinal tract. Gastrolith comes from the Greek gastro meaning stomach and lithos meaning stone. Gastroliths are retained in the muscular gizzard and used to grind food in animals lacking suitable grinding teeth. The grain size depends on the size of the animal and the Gastrolith’s role in digestion. Other species use Gastroliths as ballast. Particles ranging in size from sand to cobbles have been documented.
So how do we know Gastroliths are not just random smooth stones? Well there’s two give-aways. Firstly it helps if a few stones are found together in the right area of the crocodile/alligator/herbivorous bird/sealion/seal or dinosaur’s skeleton. Secondly, the surface of the rock should be smooth because of its use of grinding, but any indents should not be smooth – which helps to indicate its use as grinding, instead of other wearing possibilities such as water erosion.
Moqui Marbles – Also called Martian Blueberries due to their size and shape. They are most commonly found in the Navajo Sandstone in the US. The word Moqui means ‘A dearly departed one’ in the Hopi Indian language. The legend that surrounds these iron oxide concretions is that the ancestors of the Hopi played with these marbles in the evening, when the spirits are allowed to visit the Earth. As the sun rises and they go back to the heavens, they leave the marbles so their relatives know that they are happy and well.
Otoliths – Also called Statoconium or Otoconium. Otoliths are a structure in the inner ear. Otoliths are sensitive to gravity and linear acceleration. All animals including us, humans, have Otoliths and are great indicators of the age and size of the animal.
Plants or Animals found in Nodules – A great fossil phenomena. The animal or plant is killed, and sinks to the botton of the water. Sediments from floodwaters bury the plant/animal and chemical actions start. Continued chemical actions precipitated a type of gel around the body and the concretion is complete. This is the way an amazing variety of insects, small mammals, fish and plants have been found. The best thing about nodules are that they get a great colourful border and the presentation of the fossils is easy and attractive.
So once found, how to we open these nodules? Well there’s two common methods. To split open, one method is to rest the nodule on a hard rock such as granite and strike with a hammer. The second is to imitate mother nature and placing the concretions in a freezer then thawing them. This process could take a few times – roughly 4 – 20 times.
Coprolite – Also called fossil poo. A coprolite is fossilised animal dung. Coprolites are classified as trace fossils and derives from the Greek word kopros meaning dung and lithos meaning stone. Coprolites have had much of their original composition replaced by minerals such as silicates and calcium carbonates. Found inside, aswell as the remains of the diet, could possible be small bones and other such items.
Trionyx Scute – Trionyx are a soft-shelled turtle and are much rarer than the common turtle. Scute is essentially the shell. Its genus lived during the cretaceous, but survived the KT extinction, and still exists today. Currently the shell never grows longer than 20 inches but during the Eocene they have been found to be up to 40 inches long.
Mouthplates – Also called ‘teeth’. Most commonly found for Pufferfish of Parrotfish. Their teeth are fused together into a parrot-like beak and their crushing mouth plates, on the roof of their mouth, are used to grind and crush hard bodied food like sea urchins, hermit crabs and other molluscs.
Bothriodon – A large hippo-like mammal, an extinct genus of anthracotheriid artiodactyls from the late Eocene era. Have incredibly interesting bones that can be bought cheaply.
Indochinite Tektites – Tektites are natural formations of glass that has fallen back to Earth from outsude the Earth’s atmosphere following comet/large meteorite impacts. This variety of Tektite is known as an Indochinite due to the believed impact site near Thailand some 750,000 years ago when millions of tones of molten rock was projected high into the Earths’ atmosphere and into orbit. This material eventually fell back to Earth in a huge shower of shooting stars. The resultant field of material from space is known as a strew field and this stretched across much of the Earths’ surface from Australia to as far as China.
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