Contact SGS & links to other relevant geology sites

 

Fossils can be used to identify the sort of environment that existed when a particular rock was laid down.  Just like today different animals lived in different environments and some of the remains of these animals (particularly those with hard internal or external skeletons) are preserved in the rocks which formed from sediments that covered the animal when it died (fossilisation in action).  Most of the fossils in Shropshire are marine creatures but even within the sea there are lots of environmental variations that determine which animals lived where.

Click here to visit a good site that shows how fossils were formed (and thank you to Mr Maloney Jr for suggesting this!).

Many sites in Shropshire are known as good fossil collecting areas and at many others the odd fossil or two may be found with perseverance or luck.  Here is an over view of the main fossil types and some of the more common genera that may be found, including the possible environments in which they would have lived.  Please note that the pictures are not life size.

For more information on fossils and where you can find them in Britain try looking at the UK Fossils Network website.

 

TRILOBITES: so called because they have three lobes: the head (cephalon), the body (thorax) and the tail (pygidium).  Some of these animals could roll up like a 'pill-bug'. They had a hard exoskeleton which is why they can be preserved quite well.  They were all marine and lived at a range of depths and the fossils are found mostly in shales, siltstones and mudstones.   Trilobites first appear in the Cambrian period but died out during the Permian.  They are most commonly found in Cambrian, Ordovician and Silurian rocks.  Their track are also sometimes found preserved showing that at least some of the species walked along the bottom (benthic), others were free swimmers and others might just have drifted with currents (pelagic).  Many species have compound eyes like those of flies.

Asaphellus - A Cambrian trilobite.

Callavia  - A Cambrian trilobite. Calymene  - An Ordovician and Silurian trilobite.

Onnia gracilis - An Ordovician trilobite found in rocks of the Caradoc series in the Onny Valley.

Dalminites - A Silurian trilobite

 Ampyx linleyensis - An Ordovician trilobite.

This is one impression of what one type of trilobite might have looked like when it was alive


GRAPTOLITES: These are tiny marine creatures that lived in colonies.  The fossilised remains of these colonies often look like tiny hack-saw blades.  It is likely that most of these colonies floated freely on ocean currents (pelagic) although some may have been attached to rocks on the seabed.  They lived in deeper water and their fossils are mostly found in deep water shales.  They underwent rapid evolution from the first that appeared in the Cambrian period to when they went extinct in the Carboniferous period.  Because of this evolution they are very useful fossils for comparative dating of rocks in which they are found.


BRACHIOPODS: Marine animals covered by two shells joined at a hinge.  They look superficially similar to shells such as mussels and cockles but have a different plane of symmetry (see diagram).   They would have lived in mostly in shallow seas but different species are known to have lived at different depths and this is useful in determining the palaeo-environment in which sediments were laid down.  Their calcite shells mean they preserve quite well and are one of the most common groups of fossils found in Shropshire.  They were mostly attached to the sea-bed or rocks but some also buried into the sediment.  They have been found in the fossil record from the Cambrian to Recent but today only a few species still exist, one being Lingula that has persisted unchanged since the Cambrian.

Ourisia a Cambrian brachiopod

 

BIVALVES:  This is one group of fossils that are familiar to us as the group persists in many forms today.  These are superficially similar to Brachiopods but their symmetry is different (see diagram).  In bivalves the two valves are usually identical to each other and are joined along a hinge line.  They have a variety of lifestyles.  Some attach to rocks, such as mussels others burrow in the sand (e.g. razor shells) others may move freely by opening and closing their valves (e.g. scallops).  Bivalves have been around since the Cambrian but they were not so common as they are today.

Pseudopecten a Jurassic bivalve 


 CRINOIDS:  also known as 'sea-lilies' because of their plant like appearance or 'feather stars'.


 CORALS: These are a group of animals that are associated with coral reefs. They can either be solitary (one soft bodied animal in its own calcareous protective structure) or colonial (lots of individual animals in a protective mass).


 GASTROPODS

Snail.

A cross section through a gastropod. Pink is the fleshy body that rots quickly and so will rarely be preserved. Yellow is the hard calcareous shell which is much more likely to be fossilised.


CEPHALOPODS: These creatures were molluscs and were very similar to modern squid or cuttlefish except they had an external shell which they used for buoyancy control.

This shows the internal structure of a typical Cephalopod. The orange is the soft body parts and the yellow is the hard outer shell. They would have swum in much the same way as squid do today using siphons and 'jet propulsion'.

Cephalopod shells are rarely found whole. It is much more usual to find one septa (the cross pieces from the shell). These are small, smooth discs with a depression in the middle.


AMMONITES: These are a curled up version of the cephalopods above. They have the same sort of shell split into sections and they would have moved and fed in much the same manner.

Amaltheus - A Jurassic ammonite

This is one impression of what an ammonite may have looked like when swimming through the ocean.
 


PLANTS: Although plants are mostly made of soft material they will fossilise in the right conditions. Coal is essentially fossilised plants. Although in coal most of the plant material is very fragmented you may occasionally find larger pieces that are recognisable. These will mostly be bits of fern like plants.

One type of plant fossil.


FISH: Parts of (or very occasionally whole) fish can be found in sandstones and in the unit known as the Ludlow Bone Bed. Some of the earliest known fish can be found in the rocks of South Shropshire.

Bothriolepis - a Devonian fish


 OTHER FOSSILS

Ostracod.


Not all fossils are of the animals themselves.  This is a picture of fossilised worm burrows and tracks.  This is known as bioturbation..