Common Fossils UK

Name of fossilized organism and notes about it

Photograph of example of fossil

Ammonite

Fossils of ammonites are among the best-known fossils. The word "ammonite" comes from their spiral shape which looks a bit like rams' horns and the fact that the Egyptian god Ammon was widely depicted wearing ram's horns.

Ammonites (now extinct) were marine invertebrates that lived at the same time as the dinosaurs. Although they are classified as a type of mollusc, ammonites are thought to have had more in common with living soft-bodied sea creatures such as octopuses, squid, and cuttlefish than with today's marine animals that have a rigid outer shell for protection e.g. the nautilus species which looks a bit like fossils of ammonites.

Fossils indicate that ammonites ranged in size from approx 10 mm across to more than 1 m, one of the largest known being approx. 2 m in diameter.

Brachiopod

Brachiopods are shellfish (i.e. marine animals) that have two shells hinged together. They attach themselves to rocks using a 'foot' called a pedicle.

Although there are fossils of many types of brachiopods that are considered extinct, there are also living species of brachiopods that tend* to live in very cold water e.g. around the north and south poles and on deep ocean floors. Fossils indicate that brachiopods were particularly numerous during the Paleozoic era, approx. 542 to 251 million years ago.

Due to the existance of living species, much more is known about the biology and behaviour of brachiopods than of ammonites. Living species of brachiopods are *typically about 1 - 3 cm long and are thought to live for between 3 and 30 years.

*There are some exceptions e.g. the smallest known living brachiopod, gwynia capsula, measures only 1mm - 1.5 mm long and has been found widely distributed across the North Sea in intertidal and relatively shallow waters.

Crinoid

Crinoids are marine animals that live in both shallow waters and in depths of up to 6000m (= 6km = approx. 3.73 miles). Although there are many living species of crinoids, fossil evidence suggests that they were considerably more numerous and also more diverse in the distant past. For example, limestone believed to date from the mid-late Paleozoic era, approx. 400 to 251 million years ago, has been found to consist almost entirely of crinoid fragments.

Although they are marine animals, many living crinoids look more like beautiful underwater plants (see photos below). They feed by filtering tiny particles of food from sea water as it passes through their feather like 'arms'. The tube 'feet' are covered with a sticky mucus that also traps any food that floats past.

Above: Photographs of two examples of living crinoids (marine animals that look like plants).

Gastropod

Gastropods (or gastropoda) is the general name for the large biological category of animals that includes slugs and snails - both those that live, or lived, under water and land dwellers.

There are many different types of gastropods, including sea snails such as periwinkles welks and conches, limpets, sea slugs, freshwater snails, land snails and land slugs.

Fossils of gastropods have been dated from the Late Cambrian era, approx. 497 to 485 million years ago. There are estimated to be around 60,000-80,000 living species of gastropods and at least 15,000 prehistoric species. Despite the existance of so many living species of gastropods it is very difficult to know much about the anatomy and behaviour of gastropods found as fossils because even among living species gastropod characteristics vary considerably from species to species.

Above: Shark's tooth. Note: This is not a photograph of a fossilized shark's tooth (which are usually black, at least a dark colour).

Shark tooth

Scientists have estimated that sharks have been present in the earth's oceans for over 300 million years - some sources suggest 450 million years. After the death of a shark its soft tissues including skin, muscles and organs are usually eaten by other organisms or otherwise degraded by biochemical processes. This even applies to sharks' skeletons, which are formed from cartilage and rarely fossilized. However, sharks' teeth are considerably more long-lasting. They are also particularly abundant because sharks continually shed their teeth, in some cases approx 35,000 teeth per shark lifetime.

Some ancient civilizations used shark's teeth, possibly fossilized shark's teeth, to make tools, weapons and even decorations such as primitive jewellery.