Dinosaurs and their Ocean Friends

Introduction
Public summary: 

Ever wanted to see how big a T-rex's claws were, or how tiny its brain was? Ever wanted to touch real dinosaur bones or hold fossilised shark poo? Then this experiment is for you!

A collection of Mesozoic vertebrate fossils
Useful information
Kit List: 

Icthyosaur skull cast
Icthyosaur vertebra (in dino bits)
Pliosaur cervical vertebra
‘Biogeographic Fossils 3’ Box (inc shark coprolite, Baryonyx claw, Pliosaur/Plesiosaur finger bones)
Tyrannosaurus Rex box
‘Dino Bits’ box (Iguanodon bits)
Dapedius – a Jurassic fish (in T-Rex Box)

Packing Away: 

All fossils should be wrapped in tissue or something similar to protect them.
Wrap up Icthyosaur skull cast in bubble wrap.
Place Iguanodon fossils and Icthyosaur vertebra in "Dino Bits" box
Place Pliosaur cervical vertebra in its own box.
Place coprolite, Baryonyx claw and Pliosaur/Plesiosaur finger bones in "Biogeographic Fossils 3" box
Place T-Rex fossils and Dapedius in Tyrannosaurus Rex box

Frequency of use: 
3
Explanation
Explanation: 

Intro

This demonstration consists of a number of parts of fossilised Mesozoic vertebrates. The aim is to talk a group through a number of different animals alive during the Mesozoic – the era of the dinosaurs (Triassic, Jurassic, Cretaceous, 250-65 million years ago). The experiment includes several dinosaurs, marine reptiles, a fish, and a coprolite (fossilised excrement).

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.

An awkward question I have been asked a few times is how do we know that a given fossil is 80 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.

Children rarely get to see fossils up close, and when they do they are usually behind a glass barrier in a museum. Please encourage them to pick these specimens up, look at them, feel them, and engage as scientists in trying to work out what they are! However, make sure they are careful – we are borrowing these fossils from the Sedgwick Museum, and I’d quite like to not have to take anything back in pieces.

You may like to talk about why there are no dinosaurs alive today. The leading theory for the cause of their extinction at the end of the Cretaceous is a meteorite impact, although some scientists favour linking to a huge amount of volcanism in India which produced a vast quantity of lava now known as the Deccan Traps. Either event would have altered the climate by throwing up debris or ash into the air which may have blocked out the sun, but the volcanism would also have greatly increased CO2 levels, further contributing to rapid climate change. Technically, you could argue that not all dinosaurs are extinct – birds, which evolved from dinosaurs like Velociraptor during the Jurassic, could be called dinosaurs.

You may also like to talk about the differences between herbivores and carnivores: carnivores tend to have forward facing eyes for better depth perception; herbivores have outward-facing eyes to spot predators. Carnivores have sharp teeth to tear into flesh, herbivores have flat teeth to grind up tough plants. This is covered in more detail in the Animal Skulls experiment.

You may end up being asked the question “are these real?” Although they are all from a museum, only some of these specimens are actual fossils – the rest are casts of real fossils, so look exactly the same. You can probably tell the difference in weight between casts and real fossils, but I have included in the descriptions of the fossils which they are.

If children ask where these fossils are from, I am not exactly sure in every case, but most were found (or are casts of fossils found) along the coastlines of Dorset and NE England, as this is where cliffs of Mesozoic aged sedimentary rocks can be found.

The rest of this guide consists of a description of each fossil with an idea of what to talk about for each one. I like to take the pieces of an animal out one by one, pass them round, ask questions about them to see what the children can work out for themselves, and then tell them what they are, and show them a picture if we have one. All of these animals were alive during the Mesozoic, but not at the same time. Nevertheless, this demonstration is intended to give children an idea of the sorts of animals that were alive during this time, and of how we work things out about those animals.

Iguanodon
126-125 million years ago (Early Cretaceous)
Members of group Iguanodontia 156-65 million years ago (Late Jurassic – Early Cretaceous)

Iguanodons have had an interesting history of discovery. When they were first discovered, only a few bones were found, including a spike. Scientists’ best guess at this time was that Iguanodons looked like giant iguanas with spikes on their noses (you can see this in statues in Crystal Park). When a more complete skeleton was found, they discovered that the spikes in fact were on their thumbs, and were probably used either for defence or for foraging for food. The reconstruction was far more like today’s, except that they were thought to stand on two legs, since their back legs were slightly larger than their front legs. However, (as can be seen in the Sedgwick Museum’s rather impressive specimen) they had to break the bone in the tail to allow skeletons of Iguanodon to stand like this. It was later proposed that these dinosaurs used all four legs to walk, with evidence from footprints to back this up.
Iguanodons were herbivorous dinosaurs, roughly 10 metres long, with flat iguana-like teeth.
Fossils
- vertebra, real
- finger bone, real
- tooth, real – an opportunity to talk about the difference between carnivorous and herbivorous teeth
- bone fragments x2, real – you may be able to see lots of holes where the marrow used to be

T-Rex
67-65 million years ago (Late Cretaceous)
Members of family Tyranosauridae 83-65 million years ago (Late Cretaceous)

Tyrannosaurus, or T-Rex, was a huge carnivorous dinosaur, measuring up to 13 metres long, and chasing after prey on its powerful hind legs. Its sharp teeth made easy work of prey, and its tiny arms may have been used to grasp this prey and prevent it from escaping. Whether or not this is correct, they were certainly not useless, as they have been shown to be strong and muscled. T-Rex was most likely both a powerful hunter and a scavenger.
It has been suggested (e.g. Planet Dinosaur TV series) Tyrannosaurids and Ceratopsians (horned dinosaurs like Triceratops) simultaneously grew in size over the course of the Late Cretaceous to out-compete each other, the Ceratopsians getting larger and improving their defensive horns, and the Tyrannosaurs becoming bigger and more deadly.
Since some early Tyrannosaurids have been shown to have “protofeathers”, it has been suggested that T-Rex may too have had them. However, its large size probably meant that they were unnecessary – like large animals such as elephants today, they would not have needed any extra coating such as feathers to stay warm enough. Still, perhaps they had some remaining protofeathers rather than a full body covering?
Fossils
- Toe claw, cast
- Tooth x2, cast – again, talk about how sharp teeth are useful for carnivores
- Brain case, cast – this is a cast taken of the inside of a T-Rex’s skull, so shows the size and shape of its brain! Notice how it is smaller than our brains, despite T-Rex being so huge! This shows that dinosaurs like T-Rex weren't too bright.

Baryonyx
130-125 million years ago (Early Cretaceous)
Member of family Spinosauridae 155-84 million years ago (Late Jurassic – Late Cretaceous)

Baryonyx is unusual in that it is thought to have eaten fish. It was about 8.5 metres long, and had a long snout and sharp teeth to help it catch fish. It was a member of a family of dinosaurs called Spinosaurids, some of which had a large spiny frill on their backs, but Baryonyx did not.
Fossils
- Toe claw, cast – this was probably used for hunting. Baryonyx means “heavy claw”, but this refers to the claws on its front limbs, which were useful for fishing.

Dapedius
Late Triassic – Early Jurassic
Dapedius is a kind of fish that lived in the Mesozoic oceans. It had armoured plates and fed on mussels and sea urchins.
Fossils
- Whole specimen, flattened, real – this fish's scales have been covered in crayon by whoever borrowed it from the museum before us. It was flattened by the weight of the layers of sediment that buried it as it was fossilised.

Plesiosaur/Pliosaur
200-65 million years ago (Early Jurassic – Late Cretaceous)
Plesiosaurs and pliosaurs were closely related marine lizards that ranged in size from around 2-20m. They had sharp teeth and powerful jaws, and preyed upon a variety of other marine animals depending on their size, possibly including ammonites, fish, and other plesiosaurs. The main difference between Plesiosaurs and Pliosaurs is that Plesiosaurs have longer necks and smaller heads. The Loch Ness Monster is based on a Plesiosaur.
Fossils
- Finger bones x3, real – these were the finger bones in its flippers. It is not clear whether these are from a Plesiosaur or a Pliosaur as they are so similar
- Pliosaur cervical vertebra – this is a vertebra from a Pliosaur's neck

Ichthyosaur
245-90 million years ago (Middle Triassic – Late Cretaceous)
Icthyosaurs were 2-4m long dolphin-like marine reptiles which breathed air and could swim at up to 25mph. However, since they are reptiles and not mammals, they evolved this resemblance independently. This is called convergent evolution. They were very abundant during the Jurassic until replaced as top predator by plesiosaurs/pliosaurs. They fed on fish, squid-like animals called belemnites, and shellfish.
Fossils
- Vertebra, cast
- Skull cast, flattened, cast – this is a cast of a skull which was flattened by the weight of the layers of sediment that buried it during fossilisation. Features such as the eye socket and mouth are clearly visible.

Coprolite
This is a piece of fossilised poo. It is probably from a shark, but it is hard to be sure, since all we have is the poo! Sometimes we can tell things about animals’ diets from these, for example, if coprolite have fish scales in them.
Fossils
- Coprolite, real

Risk Assessment
Date risk assesment last checked: 
Tue, 19/01/2016
Risk assesment checked by: 
Tim Morgan Boyd
Date risk assesment double checked: 
Sat, 23/01/2016
Risk assesment double-checked by: 
Fiona Coventry
Risk Assessment: 

DESCRIPTION:
Sets of Mesozoic vertebrate fossils

RISKS:
Possible choke hazard for small children with the smallest pieces
Dropping fossils could cause injury to feet.
Dropping fossils may cause them to shatter, producing shale dust

ACTION TO BE TAKEN TO MINIMISE RISKS:
Ensure that items are not in the reach of small children.
Hold fossils over a table or close to the floor (i.e. when sitting on the floor).
Keep fossils in clear plastic bags for protection and to prevent dust if breakage occurs.

ACTION TO BE TAKEN IN THE EVENT OF AN ACCIDENT:
Contact first aider if injury occurs.

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