Spinosaurus: a dinosaur like no other

Learning about science often means learning lots of new words. Don’t worry – you can use the glossary at the end of the story to help you understand them. There, you can also find lots of cool videos and websites that are related to the story, and some fun questions to help you learn more. Happy reading!

Meet Dr Nizar Ibrahim. He’s a German-Moroccan biologist.

A drawing of Nizar. He is young, perhaps 30 years old, and has olive skin and dark hair. He is wearing expedition gear - a loose khaki shirt and t-shirt.

Nizar is a palaeontologist (pay-lee-on-toll-oh-jist). That means he’s a special kind of biologist, who studies fossils. Nizar spends his time investigating what life on Earth used to be like a long time ago, and how prehistoric animals, like dinosaurs, used to live.

Many of the dinosaurs we know and love, like the ferocious Tyrannosaurus rex, were discovered in North America. We know lots about the dinosaurs from here, but much less about dinosaurs from other continents. Expedition teams haven’t been everywhere, and many places have never been explored. This is something that Nizar wants to change.

A photograph of the Sahara Desert. Huge orange sand dunes roll across the landscape, and in the background even larger ones rise up like mountains. There is some small greenery, but the land looks harsh and dry.

Imagine a barren desert. There’s no life in sight, and the sun blazes down above you. The ground is dusty, and as you walk, your footprints are the first marks on the sand. Water is hard to find and, even though you have sunglasses on, the bright sun hurts your eyes. These are the conditions that Nizar works under, in the Sahara Desert of North Africa.

Going to the Sahara was a risky choice – many other scientists told him that he wouldn’t find anything, or that the expedition would be a waste. Luckily, it turned out to be the opposite.

Nizar and his team found many fossils of predators. Enormous predators, taller than houses; medium-sized predators that would still make you feel tiny, and several crocodile-like predators in what seemed to be an ancient river site.

A text box. It reads: Secrets in Stone: Where do fossils come from? Fossils are the only way we can learn about ancient animals like dinosaurs, and the conditions that they lived in. They are the preserved remains, or traces, of a dead organism. Fossilisation, the process by which something becomes a fossil, can only happen under very special conditions. That means that it’s rare for things to become fossilised. However, life on Earth has been around for about 3.5 BILLION years, and over that time, trillions of fossils have been formed. When most things die, their bodies are either eaten by other animals, or break down naturally in the soil. For fossilisation to occur, the body has to be preserved. In most cases, this happens when the body falls to the bottom of the sea, a lake, or a river. The water makes the soil incredibly soft, so the remains of the body can sink in. Once the remains are completely buried beneath a sediment like mud or sand, neither scavengers nor natural conditions can damage them. Over time, more and more layers of sediment build up on top of the remains, squashing and squashing the layer containing the body. Eventually, the pressure becomes so high that it turns this layer into sedimentary rock. This process doesn’t just happen overnight – it can take millions of years for fossils to form properly! Then, they just sit in the Earth until geological forces push them to the surface. Then, an adventurous palaeontologist like Nizar, or even a curious person like you, may stumble across these rocks and find the fossil inside them. So far, millions of fossils have been identified, from shells, to plant leaves, to bones, teeth, and complete skeletons. Even signs of life, like footprints and poo, can become fossilised!

These fossils weren’t found all at once. Nizar and his team had to work hard on their site, over a number of years. They focussed on a particular area in Morocco, known as the Kem fossil beds. Many fossils from the Cretaceous period have been found in these rocks over the years. Nizar hoped that, because fossils of crocodiles and turtles had been found there, he might discover something amazing – an aquatic dinosaur.


Nizar and his team searched hard, collecting fossils as they went, and eventually they found what they had been looking for – Spinosaurus. This dinosaur was described as a “dragon from deep time”. It was longer than a T-Rex and had an enormous sail across its back.

An illustration of Spinosaurus. It has a large head with a strong jaw, and a mouth full of teeth that is open in a roar. Along its back rises a huge fan, that looks like a crest. Its body is bulky. It has two powerful hind legs, and two slightly smaller front legs, which are tipped with three long fingers on each hand.

The story of Spinosaurus has mystified scientists for centuries. Its first fossils were discovered by a German palaeontologist named Ernst Stromer von Reichenbach, in 1912. However, these fossils, along with all of Ernst’s other research, were destroyed during World War 2. All that remained were a few drawings and descriptions.

This remaining evidence fascinated Nizar. When he was a little boy, dreaming of exploring far-away places and discovering dinosaurs, Spinosaurus was the one that he loved the most. Scientists still knew so little about it – but here in the Moroccan deserts, Nizar was sure there were answers.


In 2013, Nizar completed a successful trip to the Kem beds, and returned with enough fossils of Spinosaurus bonesto attempt a reconstruction of its skeleton. When they laid out all the bones, they could see that Spinosaurus was over 15 metres long – that’s about as long as TWO double-decker buses!

A drawing of Spinosaurus that is exactly the same as the one above. Beside it, taking up less than half of its length, is a small red double decker bus.

Something else about the skeleton really excited Nizar. He noticed that, like the fossils of ancient crocodiles that had been found nearby, Spinosaurus seemed to have a long, narrow skull, and short, stubby limbs. The bones also had thick walls, similar to those of modern-day penguins or manatees.

Nothing about the fossil suggested that Spinosaurus was a similar predator to Tyrannosaurus rex, which ran on strong hind legs and had a strong, broad jaw for crushing its prey. Instead, Nizar thought, the skeleton looked like something new – a dinosaur that could swim and hunt prey in water.

Every significant palaeontologist before Nizar had assumed that dinosaurs didn’t venture into the water. It was assumed that dinosaurs lived on land only, because no one had found any evidence to suggest otherwise.

There were certainly creatures around at the time that lived their whole lives in water, including the early crocodiles and turtles, as well as the famous Ichthyosaur and Plesiosaur. However, animals these were not dinosaurs. 

A text box. It reads: What is a dinosaur? Often, people use the word ‘dinosaur’ to mean any animal from prehistoric times. For scientists like Nizar, however, ‘dinosaur’ only describes a particular group of animals. You wouldn’t call all insects ‘flies’, or all sea creatures ‘dolphins’ – there are specific groups which these animals fall into, and that’s true for prehistoric animals too! The dinosaurs are a group of reptiles, that are related to modern day lizards and crocodiles. This group does not include famous prehistoric animals like ichthyosaurs and pterosaurs, even though they were around at the same time. To fit into any particular group, animals have to have a specific set of characteristics. For example, scientists group a large number of mammals including tigers, meerkats, and bears, into a group called Carnivora. These animals all have blade-like teeth, four or more toes, and a simple stomach. The group ‘dinosaur’ contains animals which lay eggs, have special holes in their skull that allow their jaws to open wide, and most importantly, have limbs that extend directly beneath their body. This is different to animals like lizards, whose legs splay out to the side. Dinosaurs walked either upright on their two hind legs, or on all fours. Either way, this leg position means that their body weight was directly supported. They were able to move more easily than lizards, and travel faster!

The idea that Nizar had discovered a dinosaur who lived and hunted in water caused strong reactions from other palaeontologists. Some were convinced by his arguments, and excited to find out more – while others challenged him. Nizar didn’t have enough evidence to convince everyone of his ideas.

A drawing of a conference. Nizar is stood at the front, and we look into the room from behind his head. He is clearly presenting to the room. Six other scientists sit around a long table. Some of them look happy and excited, while others look concerned or frustrated.

Palaeontologists like Nizar use the fossils that they find to predict how animals might have looked or acted. They can’t go back to the time of the dinosaurs to see how things really were, so they have to make educated guesses based on the evidence they can find.

One way to work out how a dinosaur might have acted, is to compare its skeleton to that of a living animal, to see what is similar and what is different. Nizar already did this, when he noticed that Spinosaurus’ skull is like a crocodile skull, and that its bones are like those of penguins.

To work out how Spinosaurus might have moved through the water as a swimming dinosaur, Nizar needed to know what its tail looked like. However, this was the one piece of information that he didn’t have.


Dinosaur tails are made of many small bones called vertebrae. Vertebrae are the bones that make up your spine. In dinosaurs, and other vertebrate animals with tails, the spine stretches down into the tail. Without finding every one of these small fossilised bones, Nizar and his team had no way of knowing what the tail really looked like.

A small drawing of some vertebrae. A line of seven vertebrae goes along the bottom, and above them are seven tail bones, which would have been attached to the vertebrae by living tissue. The bones are a creamy grey colour.

They returned to Morocco, determined to find a more complete skeleton.

Despite lots of setbacks – including scorpion stings, broken equipment, and dehydration caused by the punishing heat – the team were driven by their goal: finding the Spinosaurus tail. Their spirits were kept high by chocolate breaks, until one day they found something much sweeter: the first tail vertebrae of a Spinosaurus fossil.

The team went on to uncover over 30 fossils of tail vertebrae, which they now could match up with the original skeleton Nizar found. The fossils also looked similar to the ones Nizar had seen in drawings all those years ago – another great sign that the team were on the right track.

In the past, palaeontologists who, like Nizar, came from America or Europe, would often assume ownership of the fossils they found in other parts of the world, taking them when they returned to their home countries. However, Nizar and his team agreed that Spinosaurus should stay exactly where it belonged. They found a home for it at the Moroccan University of Casablanca.

A drawing of the Spinosaurus skeleton on a pedestal as if it were at a museum. The outline looks much the same as the earlier drawings, but from the skeleton you can see how it's wide fan and tail are attached to the vertebrae.

But before Spinosaurus could be displayed, Nizar and his team needed to put the fossils together to form something incredible: the most complete Spinosaurus skeleton ever found. They worked hard in the lab to achieve this, and excited by their success, Nizar set straight to work with testing the tail, to see if it could have helped Spinosaurus swim.

This task was too big for Nizar to do alone, so he contacted two other biologists, Stephanie Pierce and George Lauder, and asked for their help. George is a fish biologist, and the trio decided that his lab would be the perfect place to test out Spinosaurus’ swimming abilities.

There was no way that Nizar was going to use the real Spinosaurus fossils in these experiments. They were far too precious!

Instead, Nizar’s team made a replica of Spinosaurus’ tail. By taking careful measurements of each fossilised bone, they were able to work out what the tail’s outline would have looked like. Then, they drew the outline onto stiff, thick plastic and cut it out.

They made the plastic tail much smaller than the real Spinosaurus’ tail, so that it would fit into the water tanks in George’s lab. At full size, the tail would have been far too difficult to move and use in experiments!

A drawing of the small, plastic, yellow replica, attached to a metal pole, alongside an illustration of the real Spinosaurus tail. The 'real' tail is much bigger.

Now that the team had a replica Spinosaurus tail, they wanted to compare it to the tails of other animals, to see whether its shape would have allowed Spinosaurus to swim well. They made similar plastic tail replicas for four different animals: the dinosaurs Coelophysis and Allosaurus, a modern crocodile, and an amphibian, the crested newt.

Coelophysis and Allosaurus were both dinosaurs that spent all their time on land, and had long, narrow tails. If Spinosaurus’ tail acted similarly to theirs in water, Nizar could assume that Spinosaurus too spent most of its time on land.

On the other hand, crocodiles and crested newts spend almost most of their time in the water. If Spinosaurus’ tail acted like theirs did in the water, Nizar would have evidence that Spinosaurus also used its tail to swim. This would be the final piece of evidence he needed to prove that Spinosaurus is the first known aquatic dinosaur!

To test the tails, Nizar and his team attached them to a robotic controller, which made them move from side to side in the water, like a crocodile. A sensor attached to the tail recorded how efficient the tail was at moving through the water, and the amount of force it generated to push the animal forward (this is called thrust).

Nizar was so excited to receive the results. If Spinosaurus’ tail showed similar characteristics to swimming organisms, he would know for certain that his theories were correct!


The results from the experiment were in. Nizar looked nervously at the computer, and was immediately overjoyed. Spinosaurus’ tail generated far more power than the tails of the other two dinosaurs! Its broad shape, more similar to a newt’s tail than that of an Allosaurus, would have allowed it to swim fast and aggressively through the water.

A drawing of Spinosaurus underwater, chasing prey that would have been around in the Cretaceous - a strange underwater duck, a large fish, and two ammonites (small shellfish that look similar to squid).

This was the final piece of evidence needed to support Nizar’s theory that Spinosaurus was a totally new kind of dinosaur: a swimming predator that didn’t just wander into the water every so often, but actually lived there. He was so pleased!

Nizar’s results not only confirm a theory that he has worked hard all his life to defend, but also have an impact on the world of palaeontology as a whole.

When something as new and important as this is discovered, it forces scientists to change their assumptions. People always assumed that dinosaurs couldn’t swim, but now, because of Nizar, they know differently. What’s more, it opens up even more ideas for new discoveries.

Now that Nizar has shown that swimming dinosaurs existed, scientists wonder whether prehistoric waters may have been much fuller than we once thought – because where there’s one dinosaur, there are likely to be many more.

Thank you for reading!

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A text box. It reads: Glossary Allosaurus – huge carnivorous dinosaurs that lived around 150 million years ago. They measured up to 12 metres along. Despite being so large and ferocious when alone, scientists have found that they often used to gang up in packs against other dinosaurs! amphibian – animals that live both on land and in water – they need access to both to survive! Amphibians have backbones, are cold-blooded, and have smooth, slimy skin. Amphibians were the first ever animals to come onto land from the water, hundreds of millions of years ago. Some modern-day examples include frogs, toads, and newts. aquatic – growing, living, or happening in water. Aquatic animals live in water for all, or most, of their lifetime. assumption – something that is accepted as true or certain, without evidence. Carnivora – a group of mammals that includes dogs, cats, bears, hyenas, weasels, civets, raccoons, and mongooses. These animals all have blade-like teeth, four or more toes, and a simple stomach. characteristics – typical features of a particular person, place, or thing. Coelophysis – a small carnivorous dinosaur that lived on the ground. It was one of the earliest dinosaurs, as it lived around 216 million years ago. Coelophysis stood on its two hind legs and grew up to 3 metres long. Crested newt – a large species of newt, which lives in Europe. Male crested newts have a tall crest along their back and tail during the breeding season. Cretaceous period (cret-ay-shus) – describes a period of time that lasted from 145 million years ago to 66 million years ago. During this time, the Earth was warmer and more humid than it is today. Dinosaurs were the main group of land animals, and giant marine and flying reptiles also existed in great numbers. crocodile – a large predatory reptile, with long jaws and tail, short legs, and a horny-textured skin made of scales. Crocodiles spend lots of their time in water, and always live near rivers or lakes. efficient – something is efficient when it is as successful as possible, and has minimal wasted effort or cost. force – a push or pull on an object, that can cause it to accelerate, slow down, remain in place, or change shape. fossils – the remains or traces of dead organisms, preserved in rock. geological forces – forces created within the Earth. Ichthyosaur – large extinct reptiles that lived in the sea. They looked similar to modern porpoises, and grew up to about 3 metres long. Kem fossil beds – a group of rocks in North Africa that dates back to the late Cretaceous period. Many fossils have been recovered from them, including Spinosaurus, ancient crocodiles, and pterosaurs. mammals – animals that give birth to live young, feed their babies milk, and have hair on their bodies. Manatee – large aquatic mammals that mostly eat plants. They are sometimes called ‘sea cows’ because they can graze for up to 8 hours a day! palaeontologist – a scientist who studies fossils to learn about the history of life on Earth. Plesiosaur – an extinct marine reptile, that had a long neck and four paddle-like limbs. Plesiosaurs were predators that lived in the Cretaceous period and measured around 4.5 metres long. predators – meat-eating animals that only eat other animals. Some kill their own prey, while others are scavengers. prehistoric – things that are prehistoric happened before there were written human records. We describe everything that happened before humans began recording events as ‘prehistory’. preserved – maintained in its original state; prevented from breaking down. pressure – a measure of how much force is acting on an area. A strong push on a small area creates high pressure. Pterosaur – extinct flying reptiles that lived during the Cretaceous period. Pterodactyls are probably the best-known example of a pterosaur. Some of the largest pterosaurs were as tall as giraffes, while the smallest could fly around forests like modern sparrows.
A text box. It reads: Glossary (continued). reconstruction – a replication of something, that is built using whatever knowledge exists about it. replica – an exact copy or model of something, often made at a smaller scale. reptile – an animal that lays eggs and has skin that is scaly. Modern examples include crocodiles, lizards, and tortoises! Sahara Desert – a huge area of very dry land, which stretches for 4800 kilometres, across almost all of Northern Africa. The Sahara is the largest hot desert in the world! scavengers – an animal that feeds on dead or decaying material. Vultures are a good example! Many animals that hunt for living food are also scavengers, because it’s an easy way for them to get more food. sediment – small pieces of land that have been broken down. It is often found at the bottom of oceans, rivers, and lakes. Lots of different materials make up sediment, including grains of sand, mud, pebbles, minerals, fossils, and pieces of plant. sedimentary rock – rock that is made when layers of sediment are squashed against each other. The more layers are squashed in, the more pressure there is. Eventually, this pressure turns the layers into rock. sensor – an electronic device that detects and measures changes in the environment. It responds to a factor like pressure, light, or motion, and responds either with a reaction, or by recording data. skull – the bones that make up an animal head, and which protect the brain. spine – another word for ‘backbone’. The spine is a series of bones that run from the skull to the small of the back. It provides support for the body and protects the spinal cord. thrust – when force pushes or accelerates in one direction, it creates thrust. This moves the object forwards. Tyrannosaurus rex – one of the biggest carnivorous dinosaurs, which lived around 65 million years ago. They grew up to 12 metres long, and had teeth that could be as large as 30cm! T. rex also had a large brain, which helped it become a successful and formidable predator! vertebrae – small bones that make up the spine.
A text box. It reads: Hungry for more? If you’ve loved hearing about how Nizar used his curiosity and determination to discover the truth about Spinosaurus, have a think about these questions… 1. You’ve learnt a lot about dinosaurs from this story – enough to have a go at imagining one for yourself! Draw your own dinosaur, and give it a name. You can decide everything about it: think about where it lived, how it found food, and whether it lived in a group. Don’t forget to include all the key features that you’ve learnt about, to show that your dinosaur really is a dinosaur. 2. While learning about Nizar’s research, you’ve also learnt a lot about how scientists put animals in groups. Remember: animals that share a group, share similar features. Have a go at putting the mammals below into groups. Make sure you can explain your decisions, and try to use biological language. zebra lion fox killer whale donkey hamster otter tiger rabbit dog dolphin squirrel Hint: think about what the animals look like, where they live, and what they like to eat. What features do they have in common? 3. Imagine that you are Nizar, and you’re planning to travel back to the Kem beds to search for more fossils. What kinds of dinosaurs are you looking for? What do you need to bring with you, to make sure that you can safely hunt for fossils under the blazing Sahara Sun? 4. Test your learning! Have a go at these ‘true or false’ statements about fossils. Scientists who study fossils are called archaeologists. True or False? Fossils aren’t always skeletons. Plants, eggs, and even footprints can become fossilised too. True or false? Animals become fossilised when their body sinks into sediment. Sediment turns into rock over many years, preserving the remains. True or false? Most of the dinosaurs that existed became fossils. True or false? Fossils are usually found inside igneous rocks. True or false? 5. One of the most famous palaeontologists ever was called Mary Anning. She lived in England in the 1700s. Use the internet to do some research about Mary Anning. How do you think that the way she collected fossils was different from the way Nizar does? What challenges did each of them face, and how did they overcome them?

Resources

Nizar’s research paper: Ibrahim, N., Maganuco, S., Dal Sasso, C., Fabbri, M., Auditore, M., Bindellini, G., Martill, D., Zouhri, S., Mattarelli, D., Unwin, D., Wiemann, J., Bonadonna, D., Amane, A., Jakubczak, J., Joger, U., Lauder, G., Pierce, S. (2020). Tail-propelled aquatic locomotion in a theropod dinosaur. Nature. 581: 67-70

More information about Nizar and his dinosaur discoveries:

Video: Nizar talks about discovering large dinosaur bones in Africa, including Spinosaurus.

Video: Nizar talks about how his team found Spinosaurus.

Video: Nizar talks about the tail of Spinosaurus

More information about fossils:

Article: How are dinosaur fossils formed?

Video: Fossils

More information about dinosaurs:

Article: What are dinosaurs?

Article: What was the Cretaceous period like?

Acknowledgements

The research was produced not just by Dr Nizar Ibrahim, but also by the other members of his research team: Simone Maganuco; Cristiano Dal Sasso; Matteo Fabbri; Marco Auditore; Gabriele Bindellini; David Martill; Samir Zouhri; Diego Mattarelli; David Unwin; Jasmina Wiemann; Davide Bonadonna; Ayoub Amane; Juliana Jakubczak; Ulrich Joger; George Lauder, and Stephanie Pierce. They too deserve credit for this discovery – good science is often best done as a team.  

This story would not be nearly so good without its illustrations by the wonderful Alice Chen, and the advice and support of Dr. Nicola Hemmings.

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