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.

What is a fossil?


A dinosaur fossil (Mike Beauregard, Wikimedia

A dinosaur fossil (Mike Beauregard, Wikimedia)

A fossil is evidence of life from far back in the past. There are many types of fossil but the best known is bone. Bone is hard and strong and is often the only part of an animal to survive years after an animal has died. If those bones are buried, there is a chance that someone may find it millions of years later.

Other types of fossil include shells of sea animals like sea snails or oysters and clams. Plants can also be preserved and, occasionally, soft tissue like muscles, but these are very rare.

What is an ichthyosaur?


Ichthyosaur skeleton in a German museum

An ichthyosaur skeleton in a German museum

An ichthyosaur looks like a fish or maybe a dolphin, but it was actually a reptile. It lived in the Mesozoic seas while dinosaurs were walking on the land. They are not dinosaurs but they are so unlike any other reptile that palaeontologists aren’t sure what they are closely related to.

Ichthyosaurs went extinct about 90 million years ago so, unlike pterosaurs or non-bird dinosaurs, they didn’t become extinct because of a large meteor. Instead, palaeontologists think they wentextinct because newly evolved species of fish were faster and harder to catch. Other marine reptiles were more adaptable and replaced them in the late Mesozoic seas before the meteor hit.

Ichthyosaurs had fins instead of legs that they used for swimming. On their back they had a dorsal fin like those on many fish, and their tails also had a large crescent (moon-shaped) fin. They lived in the sea and were incapable of returning to land.

Most reptiles lay eggs but eggs are permeable to water. This means that if an egg falls in water then the infant inside would drown. But ichthyosaurs lived in water and couldn’t get onto land so ichthyosaurs gave birth to live young, as mammals do. Some fossil ichthyosaurs have even been found with babies half way out of the body. Palaeontologists think these ichtyosaurs died while giving birth.

Ichthyosaurs could be really large. The largest so far found is about 23m long. They also had massive eyes. One species called Opthalmosaurus has the largest eyes for its body size of any animal that has ever existed.

Here is a video of an ichthyosaur from the BBC’s Walking with Dinosaurs series:

What is a pterosaur?

A Pterosaur skeleton (David Peters, Wikimedia)

A Pterosaur skeleton (David Peters, Wikimedia)

While the dinosaurs ruled the land, the pterosaurs ruled the sky. Pterosaurs are flying reptiles that lived alongside dinosaurs during the Mesozoic period. They include the largest animals ever to fly, with some in the group being as large as a jet fighter and as tall as a giraffe.

Pterosaurs didn’t have feathers like birds but instead had a wing made of a membrane of thin skin. The wing was attached to the body and the arms and looks similar to a bat’s wing. But unlike a bats wing, a pterosaurs wing was supported by one very long finger that could be metres long (the finger is the same as our pinky finger).

Pterosaurs became extinct at the end of the Mesozoic period, 65 million years ago which freed the skies for bats and birds today.

Here is a video from the BBC’s Walking with Dinosaurs series:

What is a pliosaur?

The skull of a pliosaur (Greg Goebel, Wikimedia)

The skull of a pliosaur (Greg Goebel, Wikimedia)

Pliosaurs were big and vicious looking predators. They lived in the Mesozoic seas, and likely hunted almost anything that swam. They went extinct at the end of the Mesozoic.

Pliosaurs had very large fins instead of legs and had massive heads with rows of sharp teeth. They are quite rare fossils, and it’s usually only their skulls that are found.

One of the largest pliosaurs was found in England in Dorset. Only the skull was found, but it measured 2.4m long and palaeontologists estimate that the whole animal was about 15m. Click here for the BBC article on the find.

Here is a video from the BBC’s Planet Dinosaur about predator x, found in Dorset.

What is a plesiosaur?

Skeleton of a plesiosaur (Ballista, Wikimedia)

Skeleton of a plesiosaur (Ballista, Wikimedia)

Plesiosaurs are much like the sauropod dinosaurs in that they have an extremely long neck. They lived in the Mesozoic seas alongside ichthyosaurs and pliosaur, and went extinct at the end of the Mesozoic, 65 million years ago.

Plesiosaurs are very closely related to pliosaurs. Like pliosaurs, they had four very large fins that were used for swimming. Plesiosaurs also had very long necks and tails.

The first plesiosaur to be named and described was Plesiosaurus back in 1821. It came from the south coast of England, near Lyme Regis in Dorset. It was found by Mary Anning, one of the world’s first professional fossil collectors.



The Skull of Velociraptor (Thomas Vandenberghe, Wikimedia)

The Skull of Velociraptor (Thomas Vandenberghe, Wikimedia)

One of the stars of Jurassic Park, Velociraptor is famous name. But the real Velociraptor has very little in common with the one from the movie. It was half the size in real life and was covered in feathers.

But it was a deadly predator. In 1971 a Velociraptor was found intertwined with another dinosaur called Protoceratops and it seems that both were buried alive as the Velociraptor struggled to kill its prey.

Discovery: It was found in the 1920’s in an expedition to Mongolia. Velociraptor was named by Osborn in 1924.

Height: 1m

Length: 1.8m

Weight: 7-15kg

Where it lived: Fossils are found today in the Gobi Desert in Mongolia and China.

When it lived: Between 80-70 million years ago, in the Cretaceous.

What it ate: Whatever it could get its hands on. It was a meat-eater and there is evidence of it hunting other dinosaurs. One has even been found with a pterosaur bone in its stomach which palaeontologists believe points to scavenging.

Weapon of choice: Velociraptor was well armed. Its mouth had up to 80 sharp teeth each about 2.5cm long. It was intelligent, as smart as a dinosaur got but nowhere near as smart as an intelligent mammal.

Its weapon of choice was its 9cm long claw, one on each foot, which may have been used to cut veins of larger prey or pin down small prey. Used alongside its high speed running, Velociraptor was a deadly predator.

Weakness: Velociraptor was a killing machine but its jaw was relatively weak, and it was very small. It may have been smart and fast enough to avoid the bigger predators, but the larger plant eaters were too big for it to hunt.

Therizinosaurus cheloniformis

A giant hand belonging to Therizinosaurus. (Ghedoghedo, Wikimedia)

A giant hand belonging to Therizinosaurus. (Ghedoghedo, Wikimedia)

Therizinosaurus was one of the strangest dinosaurs known. Only fossils of its arms and legs have been found to date and those arms were weird. They were large, really large and had massive claws. Cheloniformis means “turtle form” because, when the arms were first found, scientists thought they had found a turtle.

Closely related species allow palaeontologists to suggest how Therizinosaurus looked. Most likely it had a wide body, long neck and quite a small head.

Discovery: originally found in 1948, it was named by a Russian scientist in 1954.

Height: Maybe 3m, but palaeontologists can’t be sure.

Length: It is estimated that it could be 10m.

Weight: very roughly estimated at 4500kg.

Where it lived: Mongolia

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

What it ate: Palaeontologists don’t know, the skull or stomach is the best place to find out but both are missing. They suspect it was vegetarian based on related species. 

Weapon of choice: Its claws are the longest known of any animal that has ever lived and could have measured 1m long (70cm long bone covered in a a sheath). These claws were deadly but they may have been used mainly for finding food.

Weakness: Not enough is known about this species to know its weakness but closely related species were slow and cumbersome.

Tarbosaurus baatar

Skeleton of Tarbosaurus (Eduard Solà, Wikiamedia)

Skeleton of Tarbosaurus (Eduard Solà, Wikiamedia)

Tarbosaurus was the king in the Late Cretaceous of Mongolia just as its close relative Tyrannosaurus was king in North America. Although slightly smaller than T.rex, Tarbosaurus was a big bad predator. Smart dinosaurs would avoid this two-legged killing machine.

Discovery: It was named in 1955

Height: 5.6m

Length: 1012m

Weight: 7000kg or a little less.

Where it lived: Found in Mongolia and China.

When it lived: it lived 75-70 million years ago in the Late Cretaceous.

What it ate: A meat eater, like T.rex, it would eat anything it could fit in its mouth. (they may have even been cannibals.)

Weapon of choice: a massive head with rows of teeth up to 20cm long.

Weakness: T.rex had tiny hands with just two claws; Tarbosaurus had even smaller hands that were even more useless.


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.