Fossil file

The fossil file

Sourced facts about fossils, fossil by fossil. Every fact links to its source, checked 31 Oct 2026.

What is a fossil?

A fossil is physical evidence of a prehistoric plant or animal: its preserved remains, or traces such as marks it made in the ground. [source]
Bones, teeth and shells are body fossils. Footprints and fossil poo are trace fossils. [source]
Fossilisation needs a special set of conditions, so it is actually a very rare event. Most things that die rot away completely. [source]
Around 99% of the fossils we find are from sea animals such as shellfish and sharks, because sand or mud could bury them quickly. [source]
Shark teeth are particularly common fossils. [source]

Planning a trip to look for your own? The fossil hunting guide on dinosaurs.im covers where to look in Britain, the beach code and what to take.

Mary Anning was born in 1799 in Lyme Regis, now part of the Jurassic Coast. [source]
Mary Anning had little formal education, but she could read and taught herself geology and anatomy. [source]
Lyme Regis is especially rich in ammonites, once called “Ammon’s horn”, and belemnites, whose name means “devil’s fingers”. [source]

The name megalodon means “giant tooth”. [source]
Megalodon is thought to be the largest shark, and the largest fish, that ever lived. [source]
Grown-up megalodons averaged 13 to 14 metres long, and the biggest may have reached about 24 metres. [source]
Megalodon is known from hundreds of fossil teeth, two backbones and a handful of single vertebrae. [source]

For living sharks, visit sharks.animals.im.

Ammonites were shelled relatives of the pearly nautilus. Their fossils turn up in sea rocks from the Devonian Period, which began 419 million years ago, to the end of the Cretaceous, 66 million years ago. [source]
One ammonite shell, Pachydiscus seppenradensis, measures 205 cm (6 ft 8 in) across. It is thought to be the largest shelled mollusc ever. [source]

Mammoths were elephants. Their fossils are found in Pleistocene deposits on every continent except Australia and South America. [source]
Some mammoths lived on as late as 4,300 years ago on Wrangel Island, off northern Russia. [source]

stone.ages.im has a guide to Stone Age sites in Britain, from Happisburgh and Boxgrove to Star Carr and Skara Brae.

Sabre-toothed cats are named after the long, blade-like canine teeth in their upper jaw. [source]
Smilodon was a large, short-legged cat about the size of a modern African lion. It lived in North and South America during the Pleistocene. [source]

Amber is fossil tree resin, changed chemically after being buried in the ground. [source]
The largest and most important amber deposits are along the shores of the Baltic Sea, in sands 40 to 60 million years old. [source]
Many hundreds of species of fossil insects and plants have been found trapped inside amber. [source]

Trilobites were the main arthropods in the seas of the early Palaeozoic, 541 to 252 million years ago. [source]
Trilobites died out in the Permian Period, at the end of the Palaeozoic Era. [source]

Ichthyosaurs were sea reptiles. They were most common and varied in the Triassic and Jurassic periods. [source]
Excellent ichthyosaur fossils have been found in Early Jurassic rocks in southern Germany and England. [source]
In autumn 1811, when Mary Anning was 12, her brother Joseph found a strange fossil skull. It was not the first ichthyosaur found, but it was the first to be scientifically studied and described. [source]

Mosasaurs were sea-going lizards found all over the world in the Cretaceous Period. [source]
The longest mosasaurs are estimated at 17 metres, but the most common kinds were no bigger than a porpoise. [source]
Mosasaurs competed with plesiosaurs and ichthyosaurs for food, which was mostly ammonoids, fish and cuttlefish. [source]

Crinoids are echinoderms: sea animals usually with a cup-shaped body and five or more flexible arms. [source]
Thousands of extinct crinoid species are important index fossils for the Palaeozoic. [source]

Coprolites are fossil dung. The name comes from the Greek kopros (“dung”) and lithos (“stone”). [source]
Geologist William Buckland coined the word in 1835, after he and Mary Anning recognised strange coiled lumps in Early Jurassic rocks. [source]

Dates and sizes are the sources’ own estimates, and they can change as new fossils are found.

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For the beach, the museum trip or the bedroom shelf: Fossil ID guides · Hand lenses · Fossil dig kits for kids · Ammonite fossils · Megalodon tooth replicas · Specimen boxes. These are Amazon UK search links, not endorsements of particular products. As an Amazon Associate I earn from qualifying purchases.