The Atlas of Dinosaurs

By Paula Hammond

Each year we learn more about life on earth hundreds of millions of years ago. Illustrated with full-colour photographs and colour artworks, The Atlas of Dinosaurs features current paleontological research on dinosaurs from every period and every region of the planet – from little known early dinosaurs to the best known ones such as Iguanodon and Tyrannosaurus Rex, from the smallest to the largest, from aquatic dinosaurs to prehistoric birds, and from herbivores, to carnivores to omnivores.

• Language: English
• Publisher: Amber Books Ltd
• Release date: Jun 1, 2023
• ISBN: 9781782742340

Book preview

Introduction

In popular culture, dinosaurs are often described as big, bad and dangerous to know. When talking about terrestrial creatures, like Brachiosaurus (a plant-muncher that grew up to 25m/82ft long), it’s certainly true that they were big. In an ecosystem where animals must eat to survive, it’s hard to label any creature ‘bad’, but perhaps Velociraptor, with its infamous killer claws, might fit the bill.

Ophthalmosaurus

Triceratops

And while Tyrannosaurus rex would probably top most people’s list of ‘dangerous dinosaurs’, any animal can be dangerous, especially if it weighs a few tonnes! Yet, when writing about dinosaurs it’s hard to avoid superlatives like ‘monstrous’, ‘fearsome’ or ‘deadly’.

Ouranosaurus

Apatosaurus

However, the truth is that there’s more to dinosaurs than big teeth, sharp claws and bone-crunching jaws. These amazing creatures represent a rich tapestry of life that is now long gone, but which we can still occasionally glimpse, thanks to their preserved remains. Sadly, these remains are often just that – ‘remains’: fragments, broken bones, bits and pieces. Because of this, you’ll find, as you flick through this book, the words ‘probably’ and ‘possibly’ on almost every page. Even the seemingly miraculous reconstructions carried out by scientists in the field are limited.

Velociraptor

Euoplocephalus

There’s still much that we don’t know about dinosaurs and their prehistoric neighbours, like the pliosaurs and the pterosaurs. Thankfully, as long as people continue to be fascinated by these brilliant beasts, then the work will continue. And who could fail to be fascinated by real-life ‘monsters’ even if they weren’t really that monstrous!

Postosuchus

Pteranodon

The Triassic Period

If we could travel back in time 248 million years to the end of the Permian Period, we would find an Earth that looked like an alien planet – and which had suffered a major extinction event.

At this time, almost all of the land was concentrated into one, vast super-continent that straddled the equator – Pangaea (‘all earth’). This mass was surrounded by a massive world-ocean – Panthalassa (‘all sea’). Temperatures were hot but with wild seasonal and geographical variations. In the wetter north – as far as the Pole – were lush, primitive ‘woodlands’. In the drier south were forests of impossibly giant ferns. Wildlife varied from region to region too. In the vegetation-rich south, there were huge herds of grazing herbivores. In the north, it was predators that ruled the roost.

However, this was a world in transition. Volcanoes were beginning to tear the land apart. Carbon levels were rising, poisoning the seas. Deserts were replacing the forests. Old species were dying out and new ones were appearing. In fact, the start of the Triassic is marked by a major ‘extinction event’. We don’t know what caused this, but it was so severe that it is known as the ‘Great Dying’. Up to 96 per cent of all marine species died, and this is the only period in the Earth’s history when insects too suffered a mass extinction. Following this ‘die off ’, new species evolved, including the ancestors of many modern mammals, invertebrates and amphibians. Reptiles were still the dominant animals, but change was on the way. The Earth was about to encounter the first proper members of a group that would become infamous. Welcome to the Triassic – the first Period of the Mesozoic Era – the Age of the Dinosaurs.

Cynognathus

248–206 MILLION YEARS AGO

Looking like some strange cross between a wolf and a lizard, Cynognathus belongs to a group of mammal-like reptiles that once dominated the Permian. Those who survived the great Permian-Triassic Extinction were very much a product of their time: both daring and dangerous.

Was Cynognathus a mammal, a reptile, or something in between? Fossils have been found all over the world, suggesting that these agile predators were one of the more successful groups of the Early Triassic. They were also one of the more interesting because they belong to a Class known as ‘synapsids’. This is a group that includes real mammals as well as ‘mammal-like’ reptiles. In fact, it’s easy to imagine Cynognathus as a mammal-reptile hybrid since it has characteristics of both groups.

When viewed from a distance, for instance, it walked with a typically lizard-like ‘sway’. This was because its backbone could move from side-to-side only, not up and down, which is more common in mammals. On closer examination, though, Cynognathus starts to look like a very strange reptile indeed.

Its stance – the way it held its legs, straight beneath its body – would be the first thing that you’d notice as you moved in for a closer look. The legs of reptiles are generally set to the sides of their bodies and held in a ‘bent’ position. Before they can run, they have to straighten out their legs and hoist their bellies off the ground. In contrast, Cynognathus had the sort of sleek body ‘design’ we see in mammalian hunters. Move closer still, and you’d notice fur and partially forward-facing eyes – two traits that gave Cynognathus a distinctly ‘mammal-like’ appearance. However, the most interesting features of Cynognathus wouldn’t be immediately obvious to the casual observer.

The Dino Detectives

Being a palaeontologist is a little like being a detective. Evidence is important, but so is the ability to make deductions from the clues you’ve been given. With good fossils, it can be surprisingly easy to work out what an animal that died 240 million years ago might have looked like. Figuring out exactly how it ‘lived’, though, is considerably trickier!

For instance, Cynognathus had more than one type of teeth (they were ‘differentiated’). This suggests that it would not only have been able to capture a wide range of prey but that it would also chew its food, rather than gulp it down whole, which is how most reptiles eat. Tiny ‘canals’ found in the bones around the snout hint that it had whiskers, similar to modern-day dogs.

Sometimes palaeontologists can even get clues about an animal’s life by looking at what’s ‘missing’ from a fossil. In the case of Cynognathus, fossils show that it had no ribs in the stomach region. In mammals, this area is where a large muscle called the diaphragm (which aids breathing) is located. It therefore seems logical to deduce that Cynognathus had a diaphragm. All these clues – and more – have led some dinosaur detectives to suggest that Cynognathus was more than ‘mammal-like’. They think that this creature was warm-blooded and may even have given birth to live young.

Size isn’t everything. Although stocky herbivores like Kannemeyeria were about twice the size of Cynognathus, they could easily be overwhelmed by a pack of aggressive predators. Working just like modern-day hyenas, these Cynognathus single out a young Kannemeyeria from the herd before moving in for the kill.

Injured and exhausted from its struggle, the beleaguered Kannemeyeria finally collapses. The rest of the pack promptly move in. Using their teeth and claws to tear open their prey’s thick hide, the hungry hunters begin feeding. But speed is essential. The pack must fill their bellies quickly before bigger predators move in to take their share.

Gracilisuchus

248–206 MILLION YEARS AGO

Making a living in the Mid-Triassic could be tricky. Luckily, Gracilisuchus was a capable and cunning predator. With a body designed for speed and agility, this little reptile was fast enough to catch and make a meal out of almost anything – from insects to fish.

Everyone loves a good monster story, and you can’t get more monstrous than dinosaurs. So it’s no surprise that in popular culture large, ferocious reptiles are often called dinosaurs even if they aren’t! In fact, what we so often see in films or on TV aren’t even dinsosaurs at all. They’re mosasaurs, plesiosaurs and pterosaurs, just some of the many prehistoric animals which lived – and died – alongside those more famous ‘terrible lizards’.

Even for the scientific community it can be quite difficult to differentiate true dinosaurs from these ‘other animals’. This is why, if you asked an expert to define what they meant by ‘dinosaur’, you would probably get more than one answer! An evolutionary biologist, for example, might say that dinosaurs are the group consisting of ‘Triceratops, neornithes (birds), their most recent common ancestor, and all their descendants’. Other experts might point to specific physical characteristics that all dinosaurs share, such as having legs that are held erect under the body. A simpler, equally valid, definition might be that dinosaurs are land-based ‘archosaurian’ reptiles, which lived from the Late Triassic to the Late Cretaceous Period (about 230-65 million years ago). It’s a complex subject – and becoming increasingly so, especially as new scientific techniques reveal previously unknown facts about these iconic beasts.

One thing is for certain, though: even the experts sometimes get it wrong – as the story of Gracilisuchus certainly proves.

Crocodile Confusion

Gracilisuchus fossils were first discovered in Northern Argentina which, 230 million years ago, was part of the gigantic super-continent Pangaea. Back then, this region was undergoing dramatic change. A warm, wet climate was being replaced by hotter, drier weather. Hardy conifers were beginning to replace the dominant ferns and a new group of animals – the dinosaurs – were starting to emerge. When Gracilisuchus was discovered in the 1970s, it was assumed to be one of these ‘new’ dinosaurs – and it’s easy to see why. After all, it had the same long jaws, sharp teeth, blunt snout and short fore arms as many of the meat-eating theropods of the Late Triassic Period. It even ran on two legs.

It took almost a decade to uncover the real facts about this feisty little predator, although the famous American palaeontologist Alfred Sherwood Romer (1894–1973) suggested the truth back in 1972.

Romer was passionate about evolution and comparative anatomy. His work involved the study of how animals change and evolve physically over time. The knowledge he acquired led Romer to realize that Gracilisuchus wasn’t a dinosaur at all. This was a difficult claim to prove, and he did not have the aid of modern scientific techniques, but we now know that he was correct. Gracilisuchus isn’t a dinosaur, but an early ancestor of the crocodile.

Gracilisuchus may have been a proficient predator, but he was also small and agile enough to make a skilful scavenger – able to literally steal food from under the noses of much larger carnivores.

Fish may also have been on the menu for our intrepid little hunter. But this time,