Tyrannosaurus rex

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A skeleton of Tyrannosaurus rex.

A skeleton of Tyrannosaurus rex.

Its name means the “terrible lizard king” and everyone knows its sharp-toothed smile.The star of countless books and films; it could be no one else but Tyrannosaurus rex.

Discovery: the first T.rex fossil was first found in 1902.

Height: 5.6m

Length: 12m

Weight: 7000kg

Where it lived: Fossils of T.rex have been found in North America. There is a very closely related  species found in Mongolia in Asia called Tarbosaurus

When it lived: it lived 67-65 million years ago in the Late Cretaceous.

What it ate: T.rex ate meat. Palaeontologists have debated whether it was a scavenger or if it hunted its own food. Teeth marks are found in other dinosaurs which match a T.rex tooth. T.rex likely did both like many animals do today.

Weapon of choice: a massive head with rows of teeth up to 20cm long. Despite its reputation from Jurassic Park, T.rex had excellent vision. Standing still wouldn’t save you if it had you in its sights.

Weakness: Its two small arms with only two fingers. Their only use was scratching its belly after a big meal.

What is sedimentation?

The Blue Lias. A cliff made out of layers of mud, sand and limestone near Lyme Regis, UK. (MichaelMaggs, Wikimedia)

The Blue Lias. A cliff made out of layers of mud, sand and limestone near Lyme Regis, UK. (MichaelMaggs, Wikimedia)

Sedimentation is very important. Without it we wouldn’t have any dinosaur fossils. It is the building up of layers of small particles like sand or mud. The easiest place to see this is the beach. A beach is made up of lots of sand which have been deposited, or left behind, by the sea.

Sand and mud come from inland. Rivers erode them from the land and bring them towards the sea. As the water slows, it can’t carry as much and so sand and mud are dropped. The bigger the grain of sand, the sooner it is dropped.

If you look at a cliff, you will often see layers which make the cliff look like a layer cake. These layers are caused by sedimentation. Over a long period of time, the grains of sand and mud build up and up, forming the layers.

Fossils are found in these layers. The quicker bones are buried, the more chance they will be saved from scavenging animals and damage by weather.

The sea, rivers and lakes are the best depositors of sand and mud and dinosaurs are found where there used to be a sea, lake or river. But big glaciers also carry grains and the air can also carry very small grains.

A land-slide, where mud and rock fall down a mountain of a sand dune can also save the bones of a dinosaur. One famous fossil called ‘The Fighting Dinosaurs’ is two dinosaurs entwined as though they are fighting. Palaeontologists think that the Velociraptor was hunting the other dinosaur, Protoceratops when a sand dune collapsed on both, killing them and preserving their bones.  

What is a species?

Drawing of some dog breeds.

Drawing of some dog breeds.

A species is a group of animals that all look similar and can have babies with any other member of that species. Humans are a species called Homo sapiens. We are one species because we all look very similar and can have children with each other.

But the members of a species can look very different from each other. Dogs are all one species called Canis lupus. This species includes every dog breed, from great danes to poodles and even wolves.

Cats, on the other hand, are a different species to dogs because a cat cannot have a baby with a dog.

Protoceratops

skeleton of Protoceratops, Wyoming Dinosaur Center. (Ovulator Wikimedia)

Skeleton of Protoceratops, Wyoming Dinosaur Center. (Ovulator Wikimedia)

Protoceratops was a small and common dinosaur. It is a relative of the much larger Triceratops. Like Triceratops it walked around on four legs, had a big frill, a bony extension of the head which covered the neck, and had a beak. But it didn’t have Triceratops’ Horns.

One Protoceratops fossil was found with a Velociraptor and it looked as though the two dinosaurs were fighting when they died. Protoceratops eggs have also been found.

Discovery: Protoceratops was found in and named in the 1920’s.

Height:  less than 1m

Length: up to 1.8m

Weight:  less than 180 kg

Where it lived: Protoceratops is found in the Gobi Desert of China and Mongolia.

When it lived: A Late Cretaceous Dinosaur, it lived 75-70 million years ago.

What it ate: A vegetarian dinosaur

Weapon of choice: Protoceratops had a strong bite but its best protection was in numbers, palaeontologists think this species travelled in herds.

Weakness:  A rather defenceless dinosaur, Protoceratops would have been easy prey if caught alone.

What is a dinosaur?

A triceratops in a museum (wikimedia)

A triceratops in a museum (wikimedia)

The name “dinosaur” means “terrible Lizard”. Englishman, Richard Owen was the man who created the name way back in 1842. The dinosaurs or Richard Owen’s world are much different from the ones we know now (look at picture below).

Two different models of Iguanodon. Top left is a modern reconstruction and bottom right is an 1854 reconstruction at Crystal Palace, London. (wikimedia sourced pictures, top: Marcus Ringer, bottom: FunkMunk)

Two different models of Iguanodon. Top left is a modern reconstruction and bottom right is an 1854 reconstruction at Crystal Palace, London. (wikimedia sourced pictures, top: Marcus Ringer, bottom: FunkMunk)

Dinosaurs were once thought of as slow cumbersome reptiles much like the komodo dragon. In the last few decades, palaeontologists have started to realise that dinosaurs were more complicated and more diverse than Owen could ever had imagined.

They lived from 248 to 65 million years ago, although most palaeontologists now believe birds are in fact modern dinosaurs. They could be huge with long necks and small heads or tiny with large brains and killer claws and teeth.

What makes a dinosaur a dinosaur?
Dinosaurs looked and act very differently to each other. Some were massive, and were over 30m long while others were the size of a chicken. Some ate meat, others ate fish and lots ate plants. Some dinosaurs walked on two legs and others walked on four. Some had very long necks while others had large horns. Some had powerful arms and claws while others had tiny arms and massive heads packed with large, sharp teeth.

But there are some things all dinosaurs had in common. Dinosaurs have an erect posture which means that their legs were straight and under the body, much like us. Most reptiles have sprawling legs, their legs come out from their sides and away from the body like any lizard or crocodile.

The two postures of reptiles.  left: sprawling posture of lizards and crocodiles. Right: erect posture of dinosaurs and mammals.

The two postures of reptiles. left: sprawling posture of lizards and crocodiles. Right: erect posture of dinosaurs and mammals.

Many animals lay eggs but dinosaurs laid eggs similar to birds and crocodiles. Their eggs are hard shelled. Other reptiles like snakes and lizards have soft shelled eggs as do fish and amphibians (and even a couple of mammals). The hard shells means that palaeontologists find the fossil remains of eggs which sometimes have baby dinosaurs still inside.

Birds are dinosaurs
Fossils show that dinosaurs had feathers like many birds and many of the first birds had teeth and clawed hands like in the famous Archaeopteryx. All the similarities between birds and dinosaurs mean that most palaeontologists now believe that birds are just modern dinosaurs.

There are over 9,000 species of birds alive today which is much more than the 5,000 mammals so maybe we are still in the age of dinosaurs after all.