Fabulous Fossils

Introduction
Public summary: 

Travel back in time through millions of years of Earth's history! If you've ever wanted to see what strange creatures lived in the past then take a look at these fabulous fossil!

A collection of various fossils (Sedgwick Musum Fossil Set 2)
Useful information
Kit List: 

Fragment of large ammonite containing other small ammonites and bivalve molluscs
Ammonite preserved in pyrite
Polished grey limestone slice containing ammonites
Sea urchin
Reef limestone slice containing corals
Colonial coral
Fragment of belemnite guard
Ammonites in grainy sandstone
Sea urchin
Ammonite preserved in pyrite
Limestone with brachiopods
Brachiopod
Productid brachiopod
Shrimp
Fragment of belemnite guard
Complete crinoid in limestone
Fan-shaped bryozoan
Ammonite preserved in pyrite
Trilobite
Gastropod sea snail (2)
Marble polished block containing gastropod sea snails
Solitary coral
Bivalve mollusc
Leaves from tree fern
Crib Sheet

Packing Away: 

Place all fossils carefully inside the relevant foam slots.

Frequency of use: 
3
Explanation
Explanation: 

Intro

This box of fossils (on loan from the Sedgwick Museum, called Fossil Set 2) has a variety of different invertebrate and plant fossils from different periods of Earth's history. This box can work well in conjunction with the Rocks and Fossils experiment. Emphasise the different morphological features of the fossils and what the creatures were like when they were alive. Possibly talk about how fossils can help you travel back in time and see what was living millions of years ago. If they seem to be old enough you should let them hold the fossils, but tell them to be very careful as they are very old.

At some point it is a good idea to ask children if they know what fossils are and how they form. If they aren’t too sure, explain how hard parts of animals – teeth, bones, shells – can be buried under layers of sediments, and eventually become fossilised. However, plants, footprints, tree sap and excrement can all be fossilised too. The fossil we see may be as it originally was, it may have recrystallised, or it may be an imprint. The details of fossilisation processes are actually very complicated, but fortunately a general idea of what happens is sufficient. The book in the box explains this for a general audience, so it's probably worth a look through.

Wikipedia says that:
"Fossils (from Latin fossus, literally "having been dug up") are the preserved remains or traces of animals (also known as zoolites), plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous (fossil-containing) rock formations and sedimentary layers (strata) is known as the fossil record. The study of fossils across geological time, how they were formed, and the evolutionary relationships between taxa (phylogeny) are some of the most important functions of the science of paleontology. Such a preserved specimen is called a "fossil" if it is older than some minimum age, most often the arbitrary date of 10,000 years ago.

Hence, fossils range in age from the youngest at the start of the Holocene Epoch to the oldest from the Archean Eon several billion years old. The observations that certain fossils were associated with certain rock strata led early geologists to recognize a geological timescale in the 19th century. The development of radiometric dating techniques in the early 20th century allowed geologists to determine the numerical or "absolute" age of the various strata and thereby the included fossils.

Like extant organisms, fossils vary in size from microscopic, such as single bacterial cells only one micrometer in diameter, to gigantic, such as dinosaurs and trees many meters long and weighing many tons. A fossil normally preserves only a portion of the deceased organism, usually that portion that was partially mineralized during life, such as the bones and teeth of vertebrates, or the chitinous or calcareous exoskeletons of invertebrates. Preservation of soft tissues is rare in the fossil record. Fossils may also consist of the marks left behind by the organism while it was alive, such as the footprint or faeces (coprolites) of a reptile. These types of fossil are called trace fossils (or ichnofossils), as opposed to body fossils. Finally, past life leaves some markers that cannot be seen but can be detected in the form of biochemical signals; these are known as chemofossils or biomarkers."

An awkward question I have been asked a few times is how do we know that a given fossil is 50 million years old? This is a hard one to answer, since most of the fossils are old enough to be dated using Uranium decay series. If children are old enough to understand Carbon-dating, you can make an analogy with this, otherwise you may have to make do with talking about relative dating using layers of sedimentary rocks.
The timeline should be useful for talking about ages of various fossils, since large numbers of years become a bit meaningless, but saying that something lived twice as long ago as the first dinosaurs impresses most children.

F80-82, 87, 97: Ammonites
These marine molluscs had spiral shells and were alive during the Mesozoic- the same time as the dinosaurs. These should not be confused with Nautilus, an animal with a spiral shell more closely related to the straight Nautiloids. They can be told apart by the position of the siphuncle – a tube used to move water between the shell’s chambers and control buoyancy – which runs along the outer edge of ammonites’ (and all ammonoids’) chambers, but through the centre of Nautiloids’. Ammonites vary in size from a couple centimetres to a couple metres, and are commonly found on the Dorset and Yorkshire coastlines.

F83: Echinoid (sea urchin)
The sea urchin is a member of a class of animals called echinoids. Echinoids are related to star-fish and tend to have a similar five-fold symmetry, though this may be less obvious depending on the specimen. During life, sea urchins are colourful balls of spikes that live on the sea-bed, feed mainly on algae, and can be found shallowly enough in warm seas such as the Caribbean that people occasionally step on their spines (which can hurt a lot!). The spines are designed to protect sea urchins against predators. They fall out within several days of the animal dying, leaving fossil sea urchins with tiny holes where each of their spines were attached during life.

F84-85, 102: Corals
Corals are another common marine invertebrate, and belong to the phylum Cnidaria (which includes jellyfish). They appear in the fossil record because they secrete a hard skeleton of calcium carbonate (better known to most people as the constituent of limestone and chalk), with the soft body of the animal generally perched on top. There are 3 types of coral: rugose and tabulate corals which flourished in the Palaeozoic but went extinct in the end-Permian mass extinction, and scleractinians which appeared in the Triassic, colonising the now-empty niche, and are the central component of modern tropical reefs.

F84: Rugose corals
Have a horn-like appearance, with diagnostic radiating septa and nearly always other internal partitions. The outside generally has prominent ridges, called rugae, which give the coral its name, and can be solitary or colonial. Here you can see a slice through a rugose coral, giving a circular shape.
(F102: A solitary rugose coral, with the horn shape more obvious.)

F85: Colonial corals
Tabulate corals are always colonial, and the zooids (small animals, also known as polyps) that secrete them are smaller than those of rugose corals. The septa, so obvious in rugosans, are almost never found in tabulates - they only have horizontal partitions (tabulae).

F86, 94: Belemnites (shell fragments)
An extinct group of squid-like cephalopods that lived during the Mesozoic era. They possessed ten tentacles studded with barbs for catching prey. They had a internal bullet-shaped skeleton called a guard with a soft body around it. This guard was made out of radiating calcite crystals. They could control their buoyancy by changing the amount of gas in the hollow phragmocone within the guard.

F90-92: Brachiopods
These shelled organisms used to be far more common, occupying many of the marine environments which bivalves do today. Their shells are made from two halves, or valves, which tend to be different, and can be distinguished by a mirror plane down the centre of each valve. They have been around since the Cambrian, and were most common during the Paleozoic.

F93: Shrimp
These decapod (10 legs) crustaceans have been around since the Mesozoic and are found in many aquatic environments around the world today. They often swim together in schools so that they are less likely to be eaten by predators. They are unusual in being able to swim backwards by lobstering. They also taste quite nice!

F95: Crinoid
Sea lilies are crinoids which are attached to the sea bed by a stalk. Crinoids have lived since the Ordovician, and, despite their name and plant-like appearance, are actually animals. They use their arms to trap small particles of food.

F96: Bryozoans
An extremely diverse phylum of marine dwelling invertebrates that have been around since the Ordovician. They could take a wide variety of forms, from long chains to spread-out fans, and their morphology often defined the structure of the sediment that they eventually created. They fed using lophophores to filter the sea water. They are actually made up of lots of tiny zooids that worked together as a colony. These zooids were able to communicate in some way so that the bryozoan as a whole could complete complex tasks.

F98: Trilobite
These are an extinct class of arthropods which lived during the Paleozoic, though they declined towards the end of it. Trilobites were some of the first animals to evolve hard parts (which is why they are also some of the earliest fossils that are regularly well-preserved) and eyes. Their hard shell meant that they could roll into a ball to protect themselves (as I think this specimen is doing). Their eyes were made from calcite crystals which had to be orientated correctly to avoid a double-image (you can demonstrate the double-image with the calcite crystal in the minerals box). Some had their eyes on stalks, while others were blind. Most moved over the sea-bed, but some swam, and they could be predators, suspension feeders or scavengers. The name trilobite refers to their three “lobes” – one that resembles a spine down the middle of the trilobite, and one on each side of it. I usually liken trilobites to woodlice to help children to imagine them.

F99-101: Gastropod
Gastropods are another group of animals which have lived in various different situations. They can be freshwater, marine, or even live on land (e.g. the snail), and have been around since the Cambrian. They can be recognised by their coiled shell. I often just use the words “sea snail” here, since I’m not sure the word “gastropod” will add much, but it’s up to you.

F103: Bivalve
These molluscs have lived in a huge variety of situations. They can be marine or freshwater, live in deep or shallow water, above or buried in the seabed, or even swim like scallops or attach themselves to rocks along the coast like mussels (both kinds of bivalve) do. Their shell consists of two usually symmetrical halves called valves, but some bivalves, such as Gryphaea (or Devil’s toenails) have one valve much bigger than the other. They have been around since the Cambrian.

F104: Tree Fern Leaves
These early tree ferns are from the Carboniferous period. At this time much of the Earth’s surface was covered in dense forests, so the levels of oxygen were very high. This lead to huge forest fires that could rage for months on end. This increase in oxygen also meant that insects and other many-legged creatures could grow to incredibly large sizes, including spiders as big as dogs and dragonflies as big as eagles! Tree ferns often hung over rivers and lakes so they fell in when they died. If the lake was anoxic then the leaves couldn’t decay and became fossilised. If lots of leaves and other plant matter were compacted together and heated they turned into coal.

Risk Assessment
Date risk assesment last checked: 
Tue, 19/12/2017
Risk assesment checked by: 
Roxanne
Date risk assesment double checked: 
Wed, 27/12/2017
Risk assesment double-checked by: 
MatthewK
Risk Assessment: 

Wooden box (on loan from Sedgwick Museum) with a variety of fossils, information card with fossil names and box layout.

Hazard Risk Likelihood Severity Overall Mitigation Likelihood Severity Overall
Small fossils Possible choke hazard for small children with the smaller fossils. Likelihood score Severity score Overall Ensure that items are not in the reach of small children.
Call a first aider in event of ingestion.
Likelihood again Severity again New overall (hopefully better than the first)
Large fossils Dropping fossils could cause injury to feet, and some may be very heavy for small children. Likelihood score Severity score Overall Hold fossils over a table or close to the floor (i.e. when sitting on the floor).
In case of injury call first aider.
Likelihood again Severity again New overall (hopefully better than the first)
Shattered fossils Dropping fossils may cause them to shatter, producing shale dust. Likelihood score Severity score Overall Make sure children check the weight before holding them.
In case of injury call first aider.
Likelihood again Severity again New overall (hopefully better than the first)
Sharp edges Fossils could be sharp and cause cut injury. Likelihood score Severity score Overall Make sure fossils have no sharp edges.
Call a first aider in event of injury.
Likelihood again Severity again New overall (hopefully better than the first)
0
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