Audio guide transcript for Jurassic Oceans: Monsters of the Deep

Jurassic Oceans: Monsters of the Deep

Journey back in time to more than 200 million years ago. Our Jurassic planet looks like a different world, with ferocious predators lurking at every turn.

Here reptiles dominate, like no other group of animals before. While one type, dinosaurs, roam the land, and flying reptiles called pterosaurs swoop through the skies, beneath the waves enormous marine reptiles rule. Seas teem with life, allowing these mighty predators to thrive. They feast on an abundance of underwater creatures, from ammonites to giant fish… and each other.

Dive into the world of mighty marine reptiles but watch out – these are perilous waters…

More than 245 million years ago, reptiles on land begin to get bigger and take over from other groups such as amphibians. This is when the formidable dinosaurs first appear.

In the waters, marine reptiles, including small, snappy ichthyosaurs have already made the sea their home.

The world has a single land mass, named ‘Pangaea’, which is beginning to separate in two. This rupture is opening vast new stretches of sea called marine corridors, which allow marine reptiles to venture into, and dominate, these new watery worlds.

Iguanodon

On land, sharp-toothed, ferocious dinosaurs hunted their prey, but there were also plant-eaters like Iguanodon, a large dinosaur with a long tail.

Size

About 10 metres long.

Hunting style

Iguanodon roamed the landscape searching for tasty plants.

Plants such as conifers and ferns.

Eyes

Faced sideways to detect predators and suss out rivals.

Mouth

A beak for grabbing tough vegetation. Large, ridged teeth for chewing and grinding.

Defence

Thumb spikes, size and bulk were likely used to defend itself.

Legs

Likely moved on four legs but could rear up.

Fierce Factor

3/10

Touch this cast of an ichthyosaur’s skull

It is based on a real fossil found in the UK.

Growing up to nine metres long, Temnodontosaurus platyodon was one of the largest types of ichthyosaur. It lived during the Triassic and Jurassic, 193–202 million years ago. Marine reptiles came in many shapes and sizes but grew bigger than ever during the Jurassic – you won’t find anything like this reptile in today’s oceans.

Jurassic marine reptiles thrive on a warm and humid Earth.

While cold areas exist, there are no polar ice caps. The ancient Tethys Ocean separates the major continents. Extensive warm, shallow waters are rich with life, host to coral reefs, fishes and sharks, allowing big predators to evolve and flourish.

What might be prey for a marine reptile is another animal’s predator. All life is intimately connected, interdependent and contributing to the health of the ecosystem.

Get ready to meet the creatures of the Jurassic seas.

Earth’s climate and atmosphere have varied over time. In the Jurassic, carbon dioxide levels in the atmosphere were high, resulting in a mostly warm and humid climate. This meant there were no polar ice caps and the sea level was higher. Life managed to adapt to these conditions.

Today, human activity is causing carbon dioxide levels to rise again, rapidly. The Sun is also slightly hotter now than it was in the Jurassic. This means the heat-trapping effect of carbon dioxide and other greenhouse gases is intensified. Today’s climate is changing faster than life can adapt to it.

Ammonites

Roaming the Jurassic waters, ammonites are related to modern octopuses, squid and nautiluses.

Size

From a few millimetres to several metres wide – an imposing sight!

Hunting style

Grabbing prey as it swam. Some would ambush prey by keeping still, then pouncing, others were likely scavengers.

Prey

Sea lilies, fishes, crabs, clams and shrimps. Smaller species likely ate plankton

Arms

Likely eight arms, possibly two tentacles for grabbing. This is uncertain, as soft body parts don’t often fossilise.

Shell

Spines and ridges for defence.

Mouth

Beak for crunching, and radula – a conveyor belt of tiny teeth – for ripping food.

Fierce factor

2/10

Touch an ancient ammonite fossil

Swimming backwards through the water, ammonites hunted sea lilies, fishes, crabs and shrimps. They would grab food with their soft, octopus-like arms and shovel it into their scoop-shaped mouth.

Fossil found in Madagascar. From the Jurassic period 145-201 million years ago.

The Jurassic seas were full of microscopic plankton, organisms that exist in the surface layers of the oceans These ones are 3D scans of phytoplankton that, like plants, use the Sun’s energy to survive. As the base of the food chain, plankton were an important meal for lots of underwater creatures, and still are today.

Jurassic corals are now-extinct animals that created similar reef environments to corals today. These reefs were probably home to a diverse array of small fish, crustaceans like crabs, and young marine reptiles. As the continents shifted and the temperature rose and fell, the reefs changed too, growing into new areas of the seabed and attracting different animals. Environments like this meant there was plenty of food for large predators.

Touch a fish’s protective scales

Feel the thickness of these scales. They were made from

tough enamel to help protect this fish from the sharp,

piercing teeth of munching predators, including

fish-eating dinosaurs.

Replica fish skin based on the species Scheenstia mantelli that lived around 145 million years ago.

Touch a Jurassic predator’s poo

Scientists aren’t sure what animal this poo comes from, but evidence of fossilised fish scales suggest it’s from a predator that had dined on fish.

It was found in the UK and is around 190-200 million years old.

Leedsichthys

Jurassic fishes ranged from snack-sized armoured fish to this gentle giant, Leedsichthys, which cruised the oceans gathering plankton for food, watchful for enormous marine reptile predators.

Size

Up to 16 metres long, the biggest bony fish to have ever lived.

Hunting style

Swimming with its mouth open to filter food from the water.

Prey

Mostly tiny plankton, probably travelling large distances to find them.

Tail

One tail sweep could move around four cubic metres of water – about 48 bathtub’s worth.

Senses

Used taste and smell to follow plankton traces

Mouth

Large mouth and strong jaw muscles to swim with its mouth open.

Teeth

Probably used for crushing ammonites, although only one fossil with fully developed teeth has been found.

Fierce factor

1/10

Leedsichthys problematicus was a gentle Jurassic giant with feeding habits similar to today’s basking shark. Opening its mouth wide, it sifted vast quantities of tiny plankton from the water. This is the only known fossilised tail fin of this animal in the world and its size would suggest this particular Leedsichthys was nine metres long. It was found in the UK and it is around 163 to 166 million years old.

Hybodus

Many different species of Hybodus sharks swam in the Jurassic seas. Like other Jurassic sharks, they were the hunted, as well as the hunters.

Size

Mostly one to two metres long.

Hunting style

Probably slow swimmers, but with fast acceleration to grab prey.

Prey

Fishes, squid-like creatures and crustaceans.

Senses

Impressive hearing, sight and smell. Could detect electromagnetic signals given off by prey.

Skin

Sharp fin spines and armoured skin made of tooth-like structures.

Teeth

Flexible jaws with pointy front teeth for gripping prey, plus crushing teeth for eating shells.

Fierce factor

4/10

The Jurassic oceans were home to many different sharks, but despite having thrived for more than 200 million years, they were still not the top predators. It’s the marine reptiles that ruled these waters. Yet Jurassic sharks like this species, Hybodus hauffianus, played a vital role as middle predators in maintaining a healthy ecosystem, balancing fish populations and as food for other predators.

This fossil was found in Germany and is between 174–183 million years old.

Glimmers of sharp teeth. The whip of a tail. A lurking shadow…

The marine reptiles are here.

Speedy ichthyosaurs chase shoals of fish, while enormous pliosaurs slash through sharks and other creatures with their powerful jaws.

Although many will survive for millions of years, the huge variety of marine reptiles in the Jurassic will never again be matched. Masters of the deep, these top predators, so vital to the balance of life in these ancient seas, truly control the waters.

Be alert at all times...

Reptiles diversified massively in the Jurassic and lived in all environments including the seas. There were many types of marine reptiles with more than 500 known species. New ones are being discovered all the time.

Rich, complex seas with abundant prey enabled them to evolve and diversify in this way, ranging from the dolphin-like ichthyosaur to ferocious pliosaurs.

These skilful hunters helped balance life in the ancient seas. By eating abundant smaller predators, they relieved pressure on the bottom of the food chain. The presence of top predators like these is a sign of flourishing habitats with plenty of prey to feast on.

Ichthyosaurs

Dolphin-like, long-snouted marine reptiles with a variety of species and sizes. The biggest ichthyosaurs weren’t necessarily the fiercest.

Size

Up to 25 metres long, similar to Hope, our blue whale specimen in Hintze Hall.

Hunting style

Speed and stealth to chase and ambush prey.

Prey

Squid-like animals, fishes, ammonites and each other!

Senses

Large eyes for hunting in dark depths and a well-developed sense of smell.

Flippers

Larger ichthyosaurs’ flipper adaptations likely reduced noise to help with stealth.

Snout

Many had long snouts with sharp teeth. Larger species were toothless gulp feeders, like some whales.

Fierce factor

8/10

A dark round patch near the front of this ichthyosaur’s ribs is the remains of its final meal including shiny fish scales, as well as the bones of a reptile – probably a small ichthyosaur. Either this small ichthyosaur was part of its final meal, or the larger ichthyosaur was pregnant when it died. Rare fossils like this can reveal snippets of these ancient predators’ eating habits.

This species of ichthyosaur is called Stenopterygius. The fossil is around 182 to 183 million years old and was found in Germany.

Touch the ancient remains of squishy squid

These pen-shaped fossils are all that remains of the soft bodies of squid-like creatures called belemnites. These animals were probably high in protein, making a valuable, high-energy snack for an ichthyosaur, which would have had no trouble swallowing a belemnite like this one whole.

These fossils are between 145-165 million years old and were found in the UK.

Long-necked plesiosaurs

Gliding swimmers with long necks and a short body. There were many different sizes and species of long-necked plesiosaur, some of which were dinner for fiercer marine reptiles.

Size

Up to 12 metres long, mostly its neck!

Hunting style

Stealth and speed to chase and catch prey.

Prey

Fishes, ammonites and shellfish.

Flippers

Four flippers, probably all used equally for power, gliding and steering.

Neck

Thin, long neck, which probably helped them sneak up on unsuspecting shoals of fish.

Teeth

Sharp, narrow teeth for catching slippery fish and cracking shells.

Fierce factor

5/10

Long-necked plesiosaur

This full plesiosaur skeleton is a cast of a fossil that was found in Japan. The species was named Futabasaurus suzukii and the fossil dates back to the Cretaceous between 84-86 million years ago.

Shark food

After it died, the remains of this long-necked plesiosaur were scavenged by sharks. Little marks show where the shark’s teeth ripped flesh from the bone. Bite marks were found on the upper bones on its front flippers and along its neck and back. Like when whales die today and fall to the sea floor, after death these animals played an important role in ecosystems, providing food for other life on the seabed.

What’s for dinner?

Fishes and shellfish similar to oysters and mussels were on the menu for long-necked plesiosaurs. Devoured remains of these creatures have been found inside the stomachs of fossilised plesiosaurs.

Marine crocodiles

A variety of reptiles with toothy snouts, but not direct ancestors of today’s crocodiles. Some looked like modern crocodiles, others more like ichthyosaurs.

Size

Up to 7.5 metres long.

Hunting style

A mixture of ambush and pursuit.

Prey

Bigger crocs ate turtles and small reptiles. Smaller ones caught fish or scavenged the sea floor for marine reptile carcasses.

Skin

Some had bony scales to protect against toothy predators such as larger marine reptiles.

Teeth

Large, conical teeth for snatching prey.

Limbs

Some had separate fingers whereas others had flippers.

Fierce factor

7/10

Feel an ancient marine croc’s armour

Can you feel the hard, bony plates under the skin of this Teleosaurus? They protected its soft internal organs from attack, making it harder for larger marine reptiles to make this croc their dinner.

This replica is based on a fossil of Teleosaurus cadomensis from the Jurassic period. The original fossil is between 164-173 million years old.

Pliosaurs

Pliosaurs were top predators and fearsome hunters of the Jurassic and included the giant Liopleurodon, with its intimidating jaws.

Size

Up to about 10 metres long, more than half the width of this gallery.

Hunting style

Possibly bursts of speed to ambush prey or chase over long distances.

Prey

Plesiosaurs, ichthyosaurs, fishes and squid-like animals.

Senses

A snout covered in nerves that sensed prey moving in the water.

Mouth

Massive jaw muscles trapped prey. A forceful bite could rip through flesh.

Flippers

Four big flippers, each up to three metres long.

Teeth

Enormous conical teeth with sharp ridges.

Fierce factor

9/10

Liopleurodon

Lower jaw

Using its long snout, which was covered in nerves, Liopleurodon could detect small electrical signals given off by other animals’ muscles. This meant it could sense the movement of prey in the water to hunt down its next meal.

Teeth

This pliosaur’s teeth could grow up to twice as long as those of a Tyrannosaurus rex! Like marine crocs, they didn’t chew their food. Once they caught their prey, they thrashed around to rip off chunks, then swallowed these whole. When Liopleurodon lost a tooth, a new one would grow in its place.

Pelvic bone

This is just one half of an adult Liopleurodon’s hip bone. It’s the biggest bone in its body and suggests that this Liopleurodon was seven metres long.

All of these fossils are from the species Liopleurodon ferox. They were found in the UK and are between 161-164 million years old.

Mosasaurs

As top predators and the ‘T. rex of the sea’, mosasaurs ruled the Cretaceous oceans several million years after the Jurassic.

Size

Up to about 15 metres long.

Hunting style

Bursts of speed to ambush and snatch unsuspecting prey.

Prey

Fishes, ammonites, other marine reptiles and even smaller mosasaurs!

Snout

Larger mosasaurs’ dense snouts were possibly used to ram prey.

Mouth

Massive, hinged jaw for swallowing large prey.

Teeth

Sharp conical teeth, plus harder teeth for crushing shells and teeth on the roof of their mouth for gripping prey.

Tail

A large tail fin made them powerful swimmers.

Fierce factor

10/10

Dare to touch a mosasaur tooth

This mosasaur tooth was found in Morocco and is between 65-68 million years old from the Cretaceous period. This mosasaur had sharp teeth for holding on to scaly fish. Some of its mosasaur relatives had especially hard teeth for crushing the shells of tasty ammonites. With more than 30 different species of these giant reptiles dominating the Cretaceous seas, each became specialised hunters for their prey.

Most marine reptiles were wiped out with the non-bird dinosaurs 66 million years ago. Only turtles survived, and their descendants live in today’s oceans. As time passed, new groups of land-based reptiles such as snakes, lizards, modern crocodiles and birds adapted to life in the seas.

After ancient marine reptiles disappeared, new kinds of predators evolved. Today’s biggest predators are sharks and marine mammals such as whales, dolphins and seals. As our oceans face drastic changes, preserving these impressive predators is essential to keeping marine ecosystems, and the planet, healthy for us all.

Saltwater crocodiles

Similar-looking to some Jurassic crocs, this species evolved from land-based ancestors in the last few million years. Their only predators are humans.

Size

Up to six metres long. One of the largest reptiles in the world today.

Hunting style

Ambush prey individually, often at night, but have also been seen hunting together.

Prey

Fishes, amphibians, crabs, turtles, deer, emu, wallabies – almost anything!

Sound

Hissing when they spot a threat.

Eyes and nostrils

Positioned on the top of the head so it can lie in wait below the water’s surface.

Mouth

Thought to have the most forceful bite of any animal today.

Fierce factor

Unrated.

How fierce do you think it is?

Orcas

The largest of the dolphins, orcas are highly social and skilled predators found across the world’s oceans. Humans are their only predator.

Size

Up to 9.8 metres long.

Hunting style

A variety of styles, from individual pursuit to cooperative ambushing.

Prey

Varies between groups. Fishes, squid or larger prey such as seals, seabirds and even whales. They are the only known predators of great white sharks.

Teeth

Sharp teeth for gripping and ripping their prey.

Communication

Languages vary between social groups and enable coordinated hunting and transfer of knowledge through generations.

Tail

Top swim speed of 50 kilometres an hour, in short bursts.

Fierce factor

Unrated.

How fierce do you think it is?

Ocean ecosystems today share many similarities with those in the Jurassic. The species may be different, but they are interdependent in similar ways. Phytoplankton produce food via photosynthesis as the foundation, fishes and squid feed on them, which are in turn hunted by predators such as seals, sharks and whales. After death, these predators’ bodies provide nutrients for other creatures, completing the cycle.

Some modern predators hunt in similar ways and have similar prey to Jurassic ones, for example orcas and pliosaurs, or dolphins and ichthyosaurs. Large predators are crucial for balanced ecosystems, and their presence is a sign of a healthy ocean. If just one species declines, or disappears, the whole ecosystem could be at risk. If we protect all aspects of marine ecosystems, including predators, we can keep the oceans healthy for us all.