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Prehistoric creatures

By VISHAL KANHAIYA04/12/20

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By VISHAL KANHAIYA

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Life

Life on Earth started around 3.8 billion years ago and has since evolved and diversified through the process of natural selection to be adapted to almost every environment possible. There are currently an estimated 1.9 million animals, plants, and other forms of life on Earth.Life can be found in every nook and cranny/niche of the globe, from the extreme environments of deep sea hydrothermal vents and the freezing conditions of the polar regions to the lush habitats found at the equator.Looking back through time, by means of the fossil and phylogenetic record, we can see that the Earth has been home to many more species than are alive today. Taking a historical perspective shows that life is constantly evolving, with the success and dominance of different groups waxing and waning over time.

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History of life on EarthThe history of life on Earth began about 3.8 billion years ago, during the Archean era, initially with single-celled prokaryotic cells, such as bacteria. Multicellular life evolved over a billion years later and it's only in the last 570 million years that the kind of life forms we are familiar with began to evolve, starting with arthropods, followed by fish 530 million years ago (Ma), land plants 475Ma and forests 385Ma. Mammals didn't evolve until 200Ma and our own species, Homo sapiens, only 200,000 years ago. So humans have been around for a mere 0.004% of the Earth's history.

Tree of lifeWith the publication of 'On the Origin of Species by means of Natural Selection' on the 24th November 1859, Charles Darwin not only explained how and why we have the diversity of life we see all around us, but also showed how all life is connected. Since then we have continued to gather evidence from a range of different disciplines including physiology, biochemistry and DNA analysis. The evidence indicates that all organisms on Earth are genetically related, a genealogical relationship that can be represented as an evolutionary tree known as the Tree of Life.The Tree of Life illustrates how different species arise from previous species via descent with modification, and that all of life is connected. The diagram above shows the relationship between the major biological groups.

The centre represents the last universal ancestor of all life on earth, the outer branches the major biological groups.The tree is based on research carried out by: David Hillis, Derrick Zwickl and Robin Gutell from the University of Texas. It is based on analysis of small sub-unit RNA sequences sampled from about 3,000 species from throughout the Tree of Life.

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Archelon

This giant turtle could live to 100 years old, possibly thanks to taking long sleeps on the seabed Type: ReptileSize: 4.6mDiet: OmnivorousPredators: Mosasaurs and sharksLived: Late Cretaceous, 75-65 million years ago Archelon was a slow mover and found most of its food drifting near the sea surface. It had little need to dive deep except when hibernating on the seabed. It was an omnivorous grazer, sweeping up drifting fish, jellyfish and dead carrion as well as plants. Its sharp, powerful beak could break open shelled animals such as ammonites.It's huge flippers suggest it was a long distance swimmer happiest in the open ocean. It would never be alone, as its huge size attracted a squadron of hangers-on such as juvenile fish as well as barnacles and parasites. It couldn't withdraw its head or flippers inside its bony shell for protection so, despite its size, it was an easy target for large predators.Like modern turtles, it laid eggs by burying them in sandy beaches under cover of darkness. Its nearest living relative is the world's largest turtle, the leatherback.

(ARK-eh-lon)

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Arsinoitherium (aars-in-oh-ith-EAR-ee-um)

Non-stop eating for this gentle giant of Eocene mangrove swamps.

Type: MammalSize: 1.8m high at the shoulderDiet: HerbivorePredators: CreodontsLived: Late Eocene and early Oligocene, from 36 to 30 million years ago.

It's most distinctive feature was the two large horns on their snouts. The horns were hollow and possibly used to produce loud mating calls as well as to compete with rival males. It was a hefty creature with thick, hairless skin resembling elephant hide.It was very selective in the types of fruit and leaves it ate. Its size meant it had to eat a lot of food - it probably spent much of its day chewing on something.It lived in small groups and would have been in the water most of the time. It couldn't straighten its legs, suggesting they were better for wading and swimming than for walking. Its large size kept it safe from most predators, although creodonts might tackle a young Arsinoitherium.

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Coelursaur

Coelurosaurs are some of the most primitive of all the dinosaurs. It is from them that we get Tyrannosaurus and other giant meat-eaters.

Around 230 million years ago the first dinosaur fossils started to be found in places such as South America, Madagascar and Europe. These dinosaurs were much smaller than their later descendents and can be divided into two groups: The prosauropod dinosaurs, which are the primitive vegetarian forerunners of sauropods such as Diplodocus, and the more common coelurosaurs which were two-legged meat-eaters that would later evolve into giants such as Tyrannosaurus and Allosaurus.The Triassic coelurosaur dinosaurs were small, nimble and built to survive in the harsh Triassic landscape. Unlike many of the four-legged lumbering reptiles around them, the coelurosaurs could use their two legs to travel at speed and to manoeuvre themselves out of dangerous situations. Their light skulls, long snout and flexible necks were ideal for hunting small animals such as insects, amphibians and other reptiles but the They could also live by scavenging when times were hard.The arrival of these dinosaurs was a landmark in evolution. They quickly evolved into newer and larger species and spread themselves around the globe until, by the start of the Jurassic period, the dinosaurs dominated the land. These helped found a dynasty that produced the largest and most feared land predators of all time. After the giant extinction event of 65 million years ago the only Earthly legacy of the dinosaurs are the birds which split from the coelurosaur dinosaurs sometime during the Late Jurassic period.

Type: Primitive theropodSize: 2-3m longDiet: CarnivorePredators: Large land reptiles like PostoschusLived: Mid Triassic to Early Jurassic, 230-200 million years ago.

(See-LUR-oh-sawr)

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A pair of the early whales known as Basilosaurus

Basilosaurus

Basilosaurus fossils were first discovered in Louisiana, USA in the 1830s. Believed to be giant reptilian sea monsters, they were named Basilosaurus, or 'king lizards'. Later, they were shown not to be reptilian but gigantic, ancient whales. They were more elongated than modern whales and had a pair of small legs, that could have been a hangover from their terrestrial ancestry. A large number of fossils of these marine predators has been found to date, leading to the conclusion that Basilosaurus were common in the warm shallow seas of the time.

Basilosaurus ("King Lizard") is a genus of cetacean that lived from 40 to 34 million years ago in the Late Eocene. Its fossilized remains were first discovered in the southern United States (Louisiana), and were initially believed to be some sort of reptile, hence the suffix -"saurus", but later found to be a marine mammal. Richard Owen wished to rename the creature Zeuglodon ("Yoked Tooth"), but, per taxonomic rules, the creature's first name remained permanent. Fossils from at least two other species of this taxon have been found in Egypt and Pakistan. Basilosaurus averaged about 18 meters (60 ft) in length, and is believed to have been the largest animal to have lived in its time. It displayed an unparalleled degree of elongation compared with modern whales. Their very small vestigial hind limbs have also been a matter of interest for paleontologists. The species is the state fossil of Mississippi and Alabama in the United States. They lived in the Eocene epoch.

Scientific name: BasilosaurusRank: GenusCommon names:king lizard

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Cymbospondylus (sim-bow-spon-DEE-lus)

It was an early member of the Icthyosaur group, which looked slightly like modern dolphins. It had no dorsal fin and its tail was long like an eel's.Its long tail made it a powerful swimmer, it patrolled in deep offshore waters looking for prey.It had a skull 1m long with short, sharp teeth good for grabbing quite large reptiles but it favored fish and cephalopods such as ammonites. These appears to have given birth to live young as it had no way to lay eggs.

A powerful dolphin-like swimmer whose sharp teeth ruled the Triassic seas.

Type: Marine reptileSize: 10m longDiet: CarnivorePredators: Few, if any, predators once fully grownLived: Late Triassic, 240-210 million years ago.

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Dunkleosteus (dunk-lee-OWE-stee-us)

Speedy, powerful and happy to eat most things - this was the creature to avoid, 360 million years ago.

Type: Placoderm fishSize: 8 to 10mDiet: CarnivorePredators: Probably noneLived: Late Devonian, 370-360 million years ago. It looked like the violent brute it was: powerfully built and armour-plated round its head. It was streamlined and shark-like. It lacked true teeth, instead it had two long bony blades that could snap and crush almost anything. Pigment cells suggest Dunkleosteus had dark colors on its back and was silvery on its belly.This fish was anything but picky with its food. It ate fish, sharks and even its own kind. And it seems that It suffered from indigestion as a result: its fossils are often associated with regurgitated, semi-digested remains of fish. It may have been one of the earliest animals to exist as male or female, meaning that pairs of fish had to mate physically.

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Elasmosaurus (eh-LAZZ-mo-SAW-rus)

A dinosaur of the seas which swam thousands of miles and could surprise its prey thanks to an incredibly long neck. Type: PlesiosaurSize: 15m longDiet: CarnivoreLived: Late Cretaceous, 85-65 million years ago.

A bizarre creature whose body was dwarfed by its long, thin neck and tail, Elasmosaurus swam using four flippers.It was a carnivorous hunter which used its long neck to get close to prey without them noticing. A swift flick of the neck could catch them unawares. Its small head limited the size of what it could eat.Elasmosaurus spent all its time in the water, often cruising coastal waters for shoals of fish. It would occasionally dive down to the seabed in shallow areas to find rounded pebbles. In its stomach, these aided digestion and provided ballast.Elasmosaurus travelled long distances to find mating and breeding grounds. There is evidence it may have given birth to live young which it reared until they were old enough to look after themselves.

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Giant Mosasaur (JY-ant MOES-ah-SAWR)

A group of supreme killers that had few enemies, except for each other.

Type: Marine reptileSize: Up to 17m in lengthWeight: maximum 20 tonnesDiet: CarnivorePredators: Probably noneLived: Late Cretaceous, 85-65 million years ago. The mosasaurs were one of the success stories of the late Cretaceous period. The largest known mosasaur is Hainosaurus, which could reach 17 metres in length. Giant mosasaurs were the top predator in the sea and were widespread across the world.Much of their day would have been spent swimming slowly near the seabed looking for suitable prey to attack. Their diet consisted of slow moving animals like ammonites, birds and turtles but they would also tackle larger and swifter prey, such as sharks and plesiosaurs, when the opportunity arose. As the mosasaurs were not fast swimmers they would have stalked their prey using natural cover provided by seaweed and rocks. Only when the prey was within striking range would the mosasaur propel itself forward. Being caught in a mosasaur’s jaws meant almost certain death.Although giant mosasaurs were the top predators in the sea, they were still vulnerable to attack. One mosasaur fossil bears the marks of a shark bite in its spine.

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460 million years ago, the biggest animal on Earth was a jet-propelled cone with tentacles.

Giant orthocone (OR-thoe-cone)

Type: Cephalopod molluscSize: Up to 11m longDiet: CarnivorePredators: Giant orthocone was the top predator of its timeLived: Late Ordovician and early Silurian, 470-440 million years ago.

The giant orthocone's living tissue was at one end of a very long conical shell. It had no fins and no tail. Along the underside of the cone ran a flexible, fleshy tube. The orthocone moved along by forcing water out in the opposite direction to where it wanted to go. It controlled its vertical position by adjusting the amount of seawater in the chambers of its shell. Its mouth and metre-long tentacles emerged from one end of the shell.It ate fish as well as arthropods, eg sea scorpions. It seized its prey using its tentacles and beak-like mouth to rip apart.

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Halisaurus (HAL-i-SAWR-uss)

The first mosasaur fossils were discovered around 1780, almost 50 years before the first dinosaur fossil.

Type: Marine reptileSize: 3-4 metres in lengthDiet: CarnivorePredators: Other mosasaursLived: Late Cretaceous, 85-65 million years ago.

Halisaurus was a mosasaur. But it was much smaller than its giant relatives like Hainosaurus. It loitered in submarine caves and and cracks. It may have waited around ledges above the water where hesperornis gathered.When the hesperornis leave their rocky ledges to dive for fish, the halisaurus are down below, waiting for an opportunity to ambush them.Mosasaur teeth are good at piercing the skin of their prey but bad at slicing flesh. So once halisaurus has caught its prey, it swallows it. Its jaw has flexible joints within it and can open incredibly wide.Like other mosasaurs, Halisaurus has extra teeth called pterygoid teeth, that it uses to hold on to its prey while its jaw moves forward to swallow the hapless victim whole.

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Hesperornis (HES-per-OR-nis)

Type: Flightless birdSize: 2m highDiet: CarnivorePredators: Sharks, plesiosaurs, dinosaursLived: Late Cretaceous, 80-65 million years ago.

This giant bird made more use of its teeth than its wings. It had a sleek, feathered body and long legs with webbed feet. Its wings were

small, used for steering when diving underwater. Its long jaws had many small sharp teeth. It was a marine predator, eating fish, ammonites and belemnites.It lived in warm seas, coming ashore only to breed. Ungainly and vulnerable on land - Hesperornis couldn't walk - they crowded together in colonies for safety and chose inaccessible rocky outcrops.It spent most of its time floating on the sea surface. It travelled long distances by a combination of swimming and drifting. It was a speedy swimmer, taking short dives to feed on shoals of fish or other passing food. Its legs could not support its weight so on land it had to push itself along on its belly. Unable to fly or walk, It needed to be wary of predators: sharks and plesiosaurs at sea, dinosaurs and pterosaurs on land.

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Leedsichthys (Leeds-ICK-thees)

It had over 40,000 teeth which were used to sieve small animals from the water. It is probably the largest fish ever to have lived.

Type: Ray-finned fishSize: Up to 27mDiet: Filter feederPredators: Liopleurodon, Metriorhynchus, Hybodus sharksLived: Late Jurassic, 165-155 million years ago It was a giant fish that would have dwarfed every other animal in the sea, but it was a gentle giant that lived on the tiny shrimps, jellyfish and small fish that make up plankton. It would have swum slowly through the upper waters of the ocean, taking mouthfuls of plankton-rich water and sieving them through the giant mesh-plates at the back of its mouth. Its feeding habits were similar to the modern blue whale, which also survives on nothing but plankton.They probably travelled large distances to find parts of the world where seasonal conditions caused plankton to form itself into a dense concentrated organic soup. Once a year, and probably after plankton feasts, Leedsichthys would have shed the giant filter plates from the back of its mouth, meaning it was unable to feed itself for several weeks, whilst the new ones grew back. Towards the end of this time it would have become weakened through hunger and vulnerable to attack.The Jurassic seas in which these lived were a dangerous place and despite its size, it had no formal means of defending itself against predators such as Liopleurodon and Metriorhynchus. One attack would be unlikely to kill a full-grown Leedsichthys, but several predators could have inflicted fatal damage, leaving this defenseless giant to die slowly from its wounds.

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Liopleurodon (LI-PLOO-ro-don)

This giant predator would dwarf a living sperm whale

Type: Marine reptileSize: 25m longDiet: OmnivorePredators: Probably noneLived: Mid to Late Jurassic, 160-155 million years It was the mightiest aquatic predator of all time. Its 25 meter long body would have cruised silently through the shallow seas of the late Jurassic, propelled by its flapping flippers.It was a hunter. Its long jaws and rows of needle-sharp teeth would have made marine crocodiles, the giant fish Leedsichthys, ichthyosaurs and even other pliosaurs vulnerable to attack.

Its nose allowed it to smell underwater. This allowed it to smell its prey from some distance away. Despite needing to breath air, It spent its entire life at sea and was unable to leave the water. Consequently, it would have given birth to its young alive and may have visited shallower water to breed. Until recently the longest confirmed adult specimen was 18 meters. But in 2003 a fossil pliosaur (possibly a Liopleurodon) was discovered in Mexico which was 18 meters long and still a juvenile - suggesting that they grew considerably larger than this.

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Megalodon (MEG-a-la-don)

Twice the size of a great white shark, and with teeth 21cm long, this was the top predator of its time.

Type: Cartilaginous fishSize: Up to 16m in lengthDiet: CarnivorePredators: No known predatorsLived: The Miocene and Pliocene epochs, 16-1.6 million years ago.

Streamlined and muscular, It had jaws over 2m wide. While it could eat whatever it chose, its favourite food was whale. Other kinds of marine mammals such as seals and Odobenocetops were also on its menu.Most of this shark's hunting was in the open sea (juveniles lived closer to shore). It attacked its prey near the surface, when it came up for air.It could swim at high speed in short bursts so tended to rush its prey from beneath. Especially when tackling large species, it would first aim to disable its prey by injuring a flipper or the tail. Once unable to swim properly, the victim would be easy to finish off.

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Metriorhynchus (MET-ri-oh-RINK-us)

This snappy hunter could grab pterosaurs in mid-flight.

Type: Marine CrocodileSize: 3m longDiet: CarnivorePredators: LiopleurodonLived: Mid Jurassic, 160-150 million years ago. At 3 meters long it was shorter than many living crocodiles but it would have been far more deadly. Its body was streamlined and its tail was long and powerful, and would have propelled it gracefully through the water by using a strong sideways sweeping motion.It was a versatile hunter, eating everything from the slow moving ammonites and belemnites to faster prey such as the giant fish Leedsichthys and even pterosaurs. It probably did this by resting with its head just under the surface so that only its nostrils remained above the surface. Then when a pterosaur strayed too close, it would give a powerful stroke with its tail and lunge out of the water, clasping the unfortunate flying reptile in its jaws. Despite its powerful hunting ability, it was relatively defenseless against other larger hunting reptiles like the liopleurodon. Unlike modern crocodiles, It lost most of its armor in order to be able to swim faster. It was so adapted to life at sea that it probably only returned to land to mate and to lay its eggs. It was not very graceful when out of the water and would have returned to the sea immediately after laying its eggs. The young would have hatched on their own, making a hazardous journey down the beach to the sea.

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Nothosaur (NOTH-oh-sawr)

A predatory reptile ahead of its time, happiest in the water but also able to haul out onto dry land.

Type: Marine reptileSize: Up to 4m longDiet: CarnivorePredators: DinosaursLived: Triassic, 240-210 million years ago. A little bit like a crocodile, Nothosaurs had a long flat tail and short stumpy legs. Plus it had a mouth full of needle-sharp teeth. Speed and agility helped it ambush fish as well as cephalopods and small reptiles.Although the water was its natural habitat, it came ashore to sunbathe. And like turtles nowadays, female Nothosaurs hauled themselves well above the high water mark to bury their clutch of eggs.

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Odobenocetops (oh-doh-ben-OH-set-ops)

This strange creature had lopsided tusks, no teeth and sucked its food out of hiding places.

Type: Marine mammalSize: 2.1m longDiet: CarnivorePredators: Megalodon sharksLived: Pliocene, 3-5 million years ago.

Its two 25cm tusks made It look like a cross between a walrus and a manatee. In males only, the right hand tusk grew much larger - up to 1.35m long. It didn't have any teeth.It cruised in shallow water staying close to the seabed where it was safest. One species had an echolocation organ, similar to that of modern dolphins.By grubbing around in the mud, It found worms and shellfish to eat. Muscular lips allowed it to suck clams out of their shells. It was an air-breathing mammal so had to rise to the surface in between dives. It used its powerful tail to swim around. It had good eyesight but despite its size, it had little defense against sharks. The tusks were not strong enough to be much use in a fight.

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Stethacanthus (STETH-ac-anth-us)

A bizarre fin marked this early shark out from the crowd in the Devonian oceans.

Type: Cartiliginous fishSize: 0.7-2m longDiet: CarnivorePredators: DunkleosteusLived: Lived 370-345 million years ago, in the late Devonian and through the Carboniferous era. It resembled modern sharks to an extent, except for its outrageous dorsal fin - the shape of an ironing board - that it seems was part of courtship display as it is found in the males only. The top of this fin was covered in rough, tooth-shaped scales that match a patch of skin on the snout of it. Was this supposed to mimic a huge mouth and make the creature appear more frightening? It tended to patrol shallow coastal waters on the lookout for food. It ate small fish, crustaceans and cephalopods (e.g. goniatites).There's evidence that It may have been migratory, returning to particular places to mate and give birth. It could certainly swim quite fast, although not quickly enough to evade a hungry Dunkleosteus.

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Tanystropheus (TAN-ee-STRO-fee-us)

Tanystropheus had a snap-off tail and the longest neck possible within the laws of physics.

Type: ReptileSize: 6m longDiet: CarnivoreLived: Late Triassic, 235-210 million years ago.

Three quarters of Its body length was its neck and tail. If its neck had been any longer its head might have snapped off. It lived in shallow waters but came ashore too. On land, It ate insects and small reptiles. In the water, it would gobble up fish and ammonites. It was not a fast swimmer so often walked along the seabed and used its long neck to get within range of prey without being noticed. Like some lizards alive today, its tail could detach if seized by a predator, to allow an escape. It would then regrow.

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Xiphactinus (zie-FAK-tin-us)

With a top speed around 60km/h, this immense fish was always likely to be "the one that got away".

Type: Bony fishSize: Up to 6m longPredators: Sharks such as CretoxyrhinaLived: Late Cretaceous, 87-65 million years ago. It had a dark blue back and light silver belly to camouflage it from above and below. Sharp teeth at one end and a powerful tail at the other combined to make it a formidable pursuit hunter. It cruised in surface waters of the oceans. It caught other large fish (swallowing creatures up to 2m long whole) and was prepared to have a go at seabirds on the surface, like a floating Hesperornis. Above all else, It was a great swimmer, able to speed towards or away from virtually anything else in the seas of the time. It may have been able to leap above the waves at times to help dislodge parasites from its skin. It was not however immune from attack. If injured, its large size meant it was easy to spot and could become prey for sharks.

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Sea scorpionsSea scorpions, or eurypterids, were the largest arthropods the world has ever seen and could grow to 2.5 metres long. They had a pair of pincers, and in some species these too could become very large. Sea scorpions were predators that were in their heyday in the Silurian and Devonian, though they survived into the Permian. The name sea scorpion is something of a misnomer, as they also inhabited freshwater and may have ventured on to land now and then. They are related to scorpions, horseshoe crabs and spiders.

Scientific name: EurypteridaRank: OrderCommon names: broad wing

HabitatsSea bedsShallow seasRivers and StreamsEstuariesWetlandsLakes and PondsIntertidal zones

A eurypterid - also known as a sea scorpion - catching the heavily armoured fish, Pteraspis

Trace fossilsIt's not only the actual bodily remains of dead animals and plants that can become fossils. Things created or left behind by animals can also fossilise, such as their footprints, burrows and dung.

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Eurypterids (sea scorpions) are an extinct group of arthropods related to arachnids which include the largest known arthropods that ever lived. They are members of the extinct order Eurypterida (Chelicerata); which is the most diverse Paleozoic chelicerate order in terms of species. The name Eurypterida comes from the Greek word eury- meaning "broad" or "wide" and the Greek word pteron meaning "wing", for the pair of wide swimming appendages on the first fossil eurypterids discovered. Eurypterids predate the earliest fishes. The largest, such as Jaekelopterus, reached 2.5 metres (8 ft 2 in) or more in length, but most species were less than 20 centimetres (8 in). They were formidable predators that thrived in warm shallow water, in both seas and lakes, in the Ordovician to Permian from 460 to 248 million years ago. Although informally called 'sea scorpions', only the earliest ones were marine (later ones lived in brackish or freshwater), and they were not true scorpions. According to theory, the move from the sea to fresh water probably occurred by the Pennsylvanian subperiod. They went extinct during the Permian–Triassic extinction event 251 million years ago, and their fossils have a near global distribution.About two dozen families of eurypterids are known. Perhaps the best-known genus of eurypterid is Eurypterus, of which around 16 fossil species are known. The genus Eurypterus was created in 1825 by James Ellsworth De Kay, a zoologist. He recognized the arthropod nature of the first ever described eurypterid specimen, found by Dr. S. L. Mitchill. In 1984, that species, Eurypterus remipes was named the state fossil of New York.

Sea scorpions

What killed them

The Permian mass extinction has been nicknamed The Great Dying, since a staggering 96% of species died out. All life on Earth today is descended from the 4% of species that survived.

BehavioursAdapted to runningAdapted to swimmingMoultingPredatorsEgg layer

When they livedOrdovician period Silurian period Devonian period Carboniferous period Permian period

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Geological timeOrigin of the Earth 4.6 billion years ago

Archean era Cryogenian period Ediacaran period Cambrian period Ordovician period Silurian period Devonian period Carboniferous period Permian period Triassic period Jurassic period Cretaceous period Palaeocene epoch Eocene epoch Oligocene epoch Miocene epoch Pliocene epoch Pleistocene epoch Holocene epoch

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Archean eraIt was during the Archean era that life first arose on Earth. At this time there were no continents, just small islands in a shallow ocean. There was a vast amount of carbon dioxide in the atmosphere, but since the sun was much fainter back then, the combined effect did not raise Earth's temperature to an extreme. Such levels of carbon dioxide would be toxic to the majority of animals alive today - as would the low oxygen levels.

Began: 3.8 billion years agoEnded: 2.5 billion years

The Archean is a geologic eon before the Paleoproterozoic Era of the Proterozoic Eon, before 2.5 Ga (billion years, or 2,500 Ma) ago. Instead of being based on stratigraphy, this date is defined chronometrically. The lower boundary (starting point) has not been officially recognized by the International Commission on Stratigraphy, but it is usually set to 3.8 Ga, at the end of the Hadean Eon. In older literature, the Hadean is included as part of the Archean. The name comes from the ancient Greek ,meaning "beginning, origin".

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Cryogenian periodA succession of incredibly harsh ice ages waxed and waned during the Cryogenian. It is nicknamed Snowball Earth as it's been suggested that the glaciation was so severe it may even have reached the equator. Life during the Cryogenian consisted of tiny organisms - the microscopic ancestors of fungi, plants, animals and kelps all evolved during this time.

Began: 850 million years agoEnded: 635 million years ago

What the Earth was like

Snowball Earth

Ice age

The Cryogenian is a geologic period that lasted from 850 to 635 million years ago. It forms the second geologic period of the Neoproterozoic Era, preceded by the Tonian Period and followed by the Ediacaran. The Sturtian and Marinoan glaciations, which are the greatest ice ages known to have occurred on Earth and may have covered the entire planet, occurred during this period. These so-called 'snowball earth' events are the subject of much scientific controversy. The main debate involves whether these glaciations were truly global or merely localised events. The period has not received the international ratification that all geological time periods undergo (the most recent being the Ediacaran Period, which was ratified in 2004). The start of the period is defined only on the ages of the rocks and not on any observable and documented global event. This is problematic as estimates of rock ages are variable and are subject to laboratory error. For instance, the Cambrian Period is marked not by rock younger than a given age (542 million years), but by the appearance of the worldwide Treptichnus pedum diagnostic trace fossil assemblage. This means that rocks can be recognised as Cambrian when examined in the field and do not require extensive testing to be performed in a lab to find a date.

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Ice ageThe last ice age hasn't ended, the climate has just warmed up a bit causing the ice sheets to retreat. When the ice was more extensive, our climate was very different. Firstly, lots of the world's water was turned to ice, so precipitation was low: Europe received roughly half the rainfall it gets today, mostly in the summer months. Globally, summer temperatures were 4-8 Celsius colder than today. In some places, the winter temperatures were 15-20 Celsius cooler than today's, making ice age Florida more like modern Quebec. Wind speeds were higher and dust storms were common as the wind picked up material from enlarged deserts and glacier margins. The ice age was at its most extreme - and the climate at its most severe - 18,000 years ago.Cryogenian

period

period when this happened

Pleistocene epoch

Carboniferous period

Permian period

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Triassic periodThe Triassic began after the worst mass extinction ever, at the end of the Permian. Life on Earth took a while to recover and diversify. The Triassic was characterised by heat, vast deserts and warm seas. Even the polar regions were warm, so lush forests grew there. However, the lack of other life, coupled with the period's particular environmental conditions, opened up some evolutionary opportunities. As a result, the very first mammals and dinosaurs evolved. During this time, the giant supercontinent of Pangaea began to break apart. The period ended as it had begun, with an extinction event that wiped out many species.

Began: Permian mass extinction248 million years agoEnded: Triassic-Jurassic mass extinction205 million years ago

What the Earth was likeDesert EarthA vast desert formed in Earth's prehistoric past when the supercontinent of Pangaea straddled the equator and stretched to the poles. Pangaea's position influenced ocean circulation patterns, and its huge size meant that there were vast areas where moist air from the oceans never penetrated.

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Jurassic periodThe Jurassic began after the mass extinction event that ended the Triassic. Life, however, was quick to recover from this blow and the Jurassic eventually became host to the most diverse range of organisms that Earth had yet seen. Amongst them were the first birds and some of the dinosaurs. Continental break-up during this time gave rise to the sea that would eventually widen to become the Atlantic Ocean. The ocean floor that formed at this time is the oldest surviving on the planet - all older ones having now been 'recycled' through plate tectonics.

Began: Triassic-Jurassic mass extinction 205 million yrs. agoEnded: 142 million yrs. ago

What the Earth was like

Types of fossils formed in this period

What grew then

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Dinosaurs were the dominant land animals for 160 million years, making them one of the most successful groups of animals ever. The name dinosaur translates as 'terrible or wondrous lizards' and they certainly evolved in a diverse range of sizes and shapes, from the gigantic plant-eating sauropods to the quick meat-eating tyrannosaurs. They also sported an impressive array of body modifications including horns, scales and crests. So far, the remains of over 1,000 different dinosaur species have been identified from fossils though technically, birds are feathered dinosaurs, meaning dinosaurs aren't really extinct at all.

Scientific name: DinosauriaRank: SuperorderCommon names:terrible, powerful, wondrous lizard

DINOSAURS

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AllosaurusThey were big, mean killing machines that reigned supreme during the late Jurassic period. They were the most common huge predators in North America 140 million years ago, reaching an impressive 12 meters in length and weighing up to four tonnes. These carnivorous dinosaurs could rip and tear chunks out of the large plant-eating sauropods and stegosaurs of the time. The enormous jaw was filled with long, serrated, back-curving teeth. Near perfect examples of this classic shaped theropod dinosaur were discovered in Wyoming and called Big Al and Big Al Two. Its fossil remains are extremely rare outside America. They lived in the JURRASIC PERIOD.

Scientific name: AllosaurusRank: Genus

Allosaurus size

Allosaurus in a dry and sandy landscape

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AllosaurusIt is a genus of large theropod dinosaur that lived 155 to 150 million years ago during the late Jurassic perio). The name Allosaurus means "different lizard". It is derived from the Greek allos ("different, other") and sauros ("lizard"). The first remains that can definitely be ascribed to this genus were described in 1877 by paleontologist Othniel Charles Marsh. As one of the first well-known theropod dinosaurs, it has long attracted attention outside of paleontological circles. Indeed, it has been a top feature in several films and documentaries about prehistoric life. It was a large bipedal predator. Its skull was large and equipped with dozens of large, sharp teeth. It averaged 8.5 meters (28 ft) in length, though fragmentary remains suggest it could have reached over 12 meters (39 ft). Relative to the large and powerful hind limbs, its three-fingered forelimbs were small, and the body was balanced by a long, heavy tail. It is classified as an allosaurid, a type of carnosaurian theropod dinosaur. It has a complicated taxonomy, and includes an uncertain number of valid species, the best known of which is A. fragilis. The bulk of Allosaurus remains have come from North America's Morrison Formation, with material also known from Portugal and possibly Tanzania. It was known for over half of the 20th century as Antrodemus, but study of the copious remains from the Cleveland Lloyd Dinosaur Quarry brought the name Allosaurus back to prominence, and established it as one of the best-known dinosaurs.As the most abundant large predator in the Morrison Formation, Allosaurus was at the top of the food chain, probably preying on contemporaneous large herbivorous dinosaurs and perhaps even other predators (e.g. Ceratosaurus). Potential prey included ornithopods, stegosaurids, and sauropods. Some paleontologists interpret Allosaurus as having had cooperative social behavior, and hunting in packs, while others believe individuals may have been aggressive toward each other, and that congregations of this genus are the result of lone individuals feeding on the same carcasses. It may have attacked large prey by ambush, using its upper jaw like a hatchet.

BehavioursCarnivorous

Egg layer

Predator

Adapted to running

Scavenger

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Archaeopteryx

Archaeopteryx are the earliest known flying birds and only about the size of a modern day magpie. Living around 150 million years ago, Archaeopteryx had developed flying abilities that may have evolved from gliding out of trees or simply running along the ground. The first complete skeleton was discovered in Jurassic limestone in Germany in 1861 and is a very important fossil, almost certainly representing the transition between reptiles and birds. This missing link shares sharp teeth and a long bony tail with small theropod dinosaurs, and a wishbone and feathers with the birds. Lived in Jurassic period

Scientific name: ArchaeopteryxRank: GenusCommon names: ancient wing, Urvogel

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ArchaeopteryxArchaeopteryx , sometimes referred to by its German name Urvogel ("original bird" or "first bird"), is the earliest and most primitive bird known. The name derives from the Ancient Greek ἀρχαῖος (archaīos) meaning "ancient", and πτέρυξ (ptéryx), meaning "feather" or "wing“. Archaeopteryx lived in the Late Jurassic Period around 150 million years ago, in what is now southern Germany during a time when Europe was an archipelago of islands in a shallow warm tropical sea, much closer to the equator than it is now. Similar in shape to a European Magpie, with the largest individuals possibly attaining the size of a raven, Archaeopteryx could grow to about 0.5 meters (1.6 ft) in length. Despite its small size, broad wings, and inferred ability to fly or glide, Archaeopteryx has more in common with small theropod dinosaurs than it does with modern birds. In particular, it shares the following features with the deinonychosaurs (dromaeosaurs and troodontids): jaws with sharp teeth, three fingers with claws, a long bony tail, hyperextensible second toes ("killing claw"), feathers (which also suggest homeothermy), and various skeletal features. The features above make Archaeopteryx a clear candidate for a transitional fossil between dinosaurs and birds. Thus, Archaeopteryx plays an important role not only in the study of the origin of birds but in the study of dinosaurs. It was named from a feather in 1861. That same year, the first complete specimen of Archaeopteryx was announced; this was only two years after Charles Darwin published On the Origin of Species, and it became a key piece of evidence in the debate over evolution. Over the years, nine more fossils of Archaeopteryx have surfaced. Despite variation among these fossils, most experts regard all the remains that have been discovered as belonging to a single species, though this is still debated.Most of these eleven fossils include impressions of feathers—among the oldest direct evidence of such structures. Moreover, because these feathers are of an advanced form (flight feathers), these fossils are evidence that the evolution of feathers began before the Late Jurassic

Behaviours

Carnivorous

Adapted to flying

Adapted to gliding

Egg layer

Predator

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Cretaceous periodThe Cretaceous ended with the most famous mass extinction in history - the one that killed the dinosaurs. Prior to that, it was a warm period with no ice caps at the poles. Much of what we now know as dry land - such as southern England and the midwest of the USA - was underwater, since sea levels reached their highest ever during this time. The Atlantic Ocean grew much wider as North and South America drew apart from Europe and Africa. The Indian Ocean was formed at this time, and the island that was India began its journey north towards Asia.

Began: 142 million years agoEnded: Cretaceous-Tertiary mass extinction65 million years ago

What the Earth was like

Causes of extinctionsFlood basalt eruptions

Impact events

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Ankylosaurus armed with thick skin, bony plates and a club like tail

Ankylosaurs

Looking like reptilian armadillos, or prehistoric tanks, Ankylosaurs were heavily armoured dinosaurs with protective plates over their head and shoulders. Some species took their protection to extremes and even had armoured eyelids. Spikes and protrusions were common in a bid to deter predators from taking a bite. Some ankylosaurs had a large, heavy club at the end of the tail for wielding as a weapon or, as has also been suggested, for sexual selection. To carry the weight of all this heavy armour, these plant-eating dinosaurs had very short, stout legs.

Scientific name: AnkylosauriaRank: InfraorderCommon names:fused lizards

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AnkylosaursAnkylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms. Ankylosaurs were bulky quadrupeds, with short, powerful limbs. They are first known to have appeared in the early Jurassic Period of China, and persisted until the end of the Cretaceous Period. They have been found on every continent except Africa. The first dinosaur ever discovered in Antarctica was the ankylosaurian Antarctopelta, fossils of which were recovered from Ross Island in 1986. It lived in both Jurassic and Cretaceous periods.Ankylosauria was first described by Henry Fairfield Osborn in 1923. In the Linnaean classification system, the group is usually considered a suborder or an infraorder. It is contained within the group Thyreophora, which also includes the stegosaurs, armored dinosaurs known for their combination of plates and spikes.

What killed themThe Cretaceous-Tertiary mass extinction - also known as the K/T extinction - is famed for the death of the dinosaurs. However, many other organisms perished at the end of the Cretaceous including the ammonites, many flowering plants and the last of the pterosaurs.

Behaviours

Predation defense

Egg layer

Herbivores

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Speculation continues over the function of the wicked looking horns and grand neck frill of the larger ceratopsians such as Triceratops. Were they for protection, display or even to control body temperature? The earliest horned dinosaurs were quite small and got about on two legs. The four legged giants that characterise the group came later. Fossil evidence suggests horned dinosaurs originated in what's now Asia during the Cretaceous period, spreading out and thriving as herbivores. Many of the species are recognised from their skulls, which seem to be the part of a ceratopsian skeleton most likely to be preserved. Lived in the Cretaceous period.

Horned dinosaursScientific name: CeratopsiaRank: InfraorderCommon names: horn face

A pair of Torosaurus dinosaurs, that are now thought to be a form of triceratops

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Ceratopsia or Ceratopia is a group of herbivorous, beaked dinosaurs which thrived in what are now North America and Asia, during the Cretaceous Period, although ancestral forms lived earlier, in the Jurassic. Early members such as Psittacosaurus were small and bipedal. Later members, including ceratopsids like Centrosaurus and Triceratops, became very large quadrupeds and developed elaborate facial horns and a neck frill. While the frill might have served to protect the vulnerable neck from predators, it may also have been used for display, thermoregulation, the attachment of large neck and chewing muscles or some combination of the above. Ceratopsians ranged in size from 1 meter (3 ft) and 23 kilograms (50 lb) to over 9 meters (30 ft) and 5,400 kg (12,000 lb).Triceratops is by far the best-known ceratopsian to the general public. It is traditional for ceratopsian genus names to end in "-ceratops", although this is not always the case. One of the first named genera was Ceratops itself, which lent its name to the group, although it is considered a nomen dubium today as its fossil remains have no distinguishing characteristics that are not also found in other ceratopsians.

Horned dinosaurs

Behaviours

Predation defence

Herbivorous

Egg layer

Adapted to running

Triceratops

Protoceratops

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Together with the bony frill behind its extraordinarily large head, the three distinctive horns of the Triceratops were traditionally viewed as defensive weapons for this mighty herbivore. However, it is likely that they were used in courtship and dominance displays, much as modern deer use their antlers. One of the last groups of dinosaur to evolve, Triceratops would have shared the landscape with, and been preyed upon by, the awesome Tyrannosaurus. There is little evidence that they ever had the spectacular battles so often depicted, however. No complete Triceratops skeleton has yet been found and what was thought to be another horned dinosaur, Torosaurus, has recently been identified as the fully mature form of Triceratops.

Triceratops

Scientific name: TriceratopsRank: GenusCommon names: three-horned face

Triceratops drinking at a pond

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Triceratops size

Triceratops is a genus of herbivorous ceratopsid dinosaur which lived during the late Maastrichtian stage of the Late Cretaceous Period, around 68 to 65 million years ago in what is now North America. It was one of the last dinosaur genera to appear before the great Cretaceous–Tertiary extinction event.Bearing a large bony frill and three horns on its large four-legged body, and conjuring similarities with the modern rhinoceros, Triceratops is one of the most recognizable of all dinosaurs and the best known ceratopsid. It shared the landscape with and was preyed upon by the fearsome Tyrannosaurus, though it is less certain that the two did battle in the manner often depicted in traditional museum displays and popular images. The exact placement of the Triceratops genus within the ceratopsid group has been debated by paleontologists. Two species, T. horridus and T. prorsus, are considered valid although many other species have been named. Recent research suggests that the contemporaneous Torosaurus, a ceratopsid long regarded as a separate genus, actually represents Triceratops in its mature form. Triceratops has been documented by numerous remains collected since the genus was first described in 1889, including at least one complete individual skeleton. Paleontologist John Scannella observed: "It is hard to walk out into the Hell Creek Formation and not stumble upon a triceratops weathering out of a hillside." Forty-seven complete or partial skulls were discovered in just that area during the decade 2000–2010. Specimens representing life stages from hatchling to adult have been found.The function of the frills and three distinctive facial horns has long inspired debate. Traditionally these have been viewed as defensive weapons against predators. More recent theories, noting the presence of blood vessels in the skull bones of ceratopsids, find it more probable that these features were primarily used in identification, courtship and dominance displays, much like the antlers and horns of modern reindeer, mountain goats, or rhinoceros beetles. The theory finds additional support if Torosaurus represents the mature form of Triceratops, as this would mean the frill also developed holes (fenestrae) as individuals reached maturity, rendering the structure more useful for display than defense.

Triceratops

Behaviours

Predation defenseHerbivorous Egg layer Courtship display

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Two protoceratops from a group fighting in the desert

Were the beak and clawed legs of Protoceratops fossil remains the origin of the lion bodied, eagle headed griffin of Greek legend? We know now that Protoceratops was an early type of horned dinosaur related to Triceratops. These herbivores would have been about the size of sheep and may have roamed in herds, devouring the vegetation of the time. Certainly, the finding of fossilised remains of many individuals in one place suggested herd behaviour. One of the two recognised finds of Protoceratops fossils was infamous for having a velociraptor skeleton wrapped around it as if locked in battle.

Scientific name: ProtoceratopsRank: GenusCommon names: first horn face

Protoceratops

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Protoceratops , (derived from Greek proto 'first', cerat‘ horn' and ‘ops’ face )is a genus of sheep-sized (1.5 to 2 m long) herbivorous ceratopsian dinosaur, from the Upper Cretaceous Period (Campanian stage) of what is now Mongolia. It was a member of the Protoceratopsidae, a group of early horned dinosaurs. Unlike later ceratopsians, however, it lacked well-developed horns and retained some primitive traits not seen in later genera.Protoceratops had a large neck frill, which may have served to protect the neck, to anchor jaw muscles, to impress other members of the species, or combinations of these functions. Described by Walter Granger and W.K. Gregory in 1923, Protoceratops was initially believed to be an ancestor of the North American ceratopsians. Researchers currently distinguish two species of Protoceratops (P. andrewsi and P. hellenikorhinus), based in part by their respective sizes.In the 1920s, Roy Chapman Andrews discovered fossilized eggs in Mongolia that were interpreted as belonging to this dinosaur, but which turned out to be those of Oviraptor.

Protoceratops

Behaviours

Predation defence

Herbivorous

Egg layer

Adapted to running

Fossil Folklore

Protoceratops have featured it our folklore - learn more our ancestors beliefs before we understood fossilisation and evolution.

Velociraptors work together to hunt down a bulky Proceratops.

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Ceropod dinosaurs were all plant-eaters and include the horned and duck-billed dinosaurs. The secret of their success was in their teeth. These were much more efficient at grinding up plant food than your typical dinosaur's dentition, so cerapods were able to extract more nutritional value from their food and tackle plants that others found too tough to digest. It wasn't until big herbivorous mammals evolved that such efficient chewing teeth were seen again on Earth.

Ceropod dinosaursScientific name: CerapodaRank: SuborderCommon names: horn foot

A group of Corythosaurus dinosaurs on a frozen landscape

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Neornithischia is a clade of the order Ornithischia. They are the sister group of the Thyreophora within the clade Genasauria. Neornithischians are united by having a thicker layer of asymmetrical enamel on the inside of their lower teeth. The teeth wore unevenly with chewing and developed sharp ridges that allowed neornithischians to break down tougher plant food than other dinosaurs

Ceropod dinosaurs

Herbivorous Egg layer

Behaviours

What killed them

Cretaceous-Tertiary mass extinction

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Ornithopod dinosaurs

With some of the most advanced chewing apparatus ever developed by a reptile, ornithopod dinosaurs became a most successful group of herbivorous dinosaurs. They rapidly became a prominent feature on North America's Cretaceous landscape, until they were wiped out by the famous Cretaceous-Tertiary, or K-T, extinction event. Early ornithopods were only about a metre long and could probably run very fast on their hind legs. They evolved to become as large as some of the mighty sauropods, walking and grazing on all four legs, but still using the hind legs for running and reaching up into trees. Notable ornithopods include the duck-billed hadrosaurs and, of course, iguanodon.

Scientific name: OrnithopodaRank: InfraorderCommon names: bird feet

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Ornithopod dinosaursOrnithopods or members of the clade Ornithopoda are a group of bird-hipped dinosaurs that started out as small, bipedal running grazers, and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world, and dominated the North American landscape. Their major evolutionary advantage was the progressive development of a chewing apparatus that became the most sophisticated ever developed by a reptile, rivaling that of modern mammals like the domestic cow. They reached their apex in the duck-bills, before they were wiped out by the Cretaceous-Tertiary extinction event along with all other non-avian dinosaurs. Members are known from all seven continents, although the Antarctic remains are unnamed, and they are generally rare in the Southern Hemisphere.

Iguanodons

Duck-billed dinosaurs

Leaellynasaura

Muttaburrasaurus

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Giant kelp viewed from underwater

ChromistaChromista include diatoms, ciliates and their relatives. As many of the species in this kingdom can photosynthesise, and have rigid cell walls, they were once thought to be plants. Their members include kelps, the water mould that caused the Irish potato famine and single-celled organisms such as the paramecium.

Scientific name: ChromistaRank: KingdomCommon names: ChromistaThe Chromista are a eukaryotic supergroup, probably polyphyletic, which may be treated as a separate kingdom or included among the Protista. They include all algae whose chloroplasts contain chlorophylls a and c, as well as various colorless forms that are closely related to them. These are surrounded by four membranes, and are believed to have been acquired from some red alga.

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Iguanodons

Plant-eating Iguanodons were large dinosaurs capable of walking on two legs or on all four. Their outstanding feature was a highly specialised, five-fingered hand made up of an erect and spiked thumb used for defence or perhaps foraging, three middle fingers and a grasping fifth finger. Iguanodons were one of the first dinosaurs ever described and artistic impressions have changed much with each new discovery. Currently, it's thought they held the head low to the ground and their long, heavy tail in the air for balance rather than vice versa. Herds of Iguanodon - the different species varying in size - flourished in Europe and North America during the lower Cretaceous period.

Scientific name: IguanodonRank: GenusCommon names: iguana tooth

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Iguanodon is a genus of ornithopod dinosaur that lived roughly halfway between the first of the swift bipedal hypsilophodontids and the ornithopods' culmination in the duck-billed dinosaurs. Many species of Iguanodon have been named, dating from the Kimmeridgian age of the Late Jurassic Period to the Cenomanian age of the Late Cretaceous Period from Asia, Europe, and North America. However, research in the first decade of the 21st century suggests that there is only one well-substantiated species: I. bernissartensis, that lived from the late Barremian to the earliest Aptian ages (Early Cretaceous) in Europe, between about 126 and 125 million years ago. Iguanodon's most distinctive features were its large thumb spikes, which were possibly used for defence against predators, combined with long prehensile fifth fingers able to forage for food.Discovered in 1822 and described three years later by English geologist Gideon Mantell, Iguanodon was the second dinosaur formally named, after Megalosaurus. Together with Megalosaurus and Hylaeosaurus, it was one of the three genera originally used to define Dinosauria. A large, bulky herbivore, Iguanodon is a member of Iguanodontia, along with the duck-billed hadrosaurs. The taxonomy of this genus continues to be a topic of study as new species are named or long-standing ones reassigned to other genera.Scientific understanding of Iguanodon has evolved over time as new information has been obtained from the fossils. The numerous specimens of this genus, including nearly complete skeletons from two well-known bonebeds, have allowed researchers to make informed hypotheses regarding many aspects of the living animal, including feeding, movement, and social behaviour.

Iguanodons Fossil typesTrace fossils

Iguanodon size

BehavioursAdapted to runningPredation defenceHerbivoresSocialEgg layer

When they livedJurassic periodCretaceous period

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Macrauchenia

The first Macrauchenia skeleton was actually discovered by Charles Darwin on a stop-over on his famous journey on board The Beagle. Since then many more remains have been found in the Lujan formation in Argentina. Although this animal looked like it should be a member of the camel family, it was actually related to a group of animals that no longer exists - the litopterns. Its strange skull suggests that it had a muscular proboscis. Little work has been done on Macrauchenia, but its ankle joints and shin bones seem to be adapted for extreme mobility, allowing it to twist and turn to avoid pursuers at high speed.

Scientific name: MacraucheniaRank: GenusCommon names: long llama

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Macrauchenia ("long llama", based on the now superseded Latin term for llamas Auchenia, from Greek terms which literally mean "big neck") was a long-necked and long-limbed, three-toed South American ungulate mammal, typifying the order Litopterna. The oldest fossils date back to around 7 million years ago, and M. patagonica disappears from the fossil record during the late Pleistocene, around 20,000 years ago. M. patagonica was the best known member of the family Macraucheniidae, and is known only from fossil finds in South America, primarily from the Lujan Formation in Argentina. The original specimen was discovered by Charles Darwin during the voyage of the Beagle. In life, Macrauchenia resembled a humpless camel with a short trunk, though it is not closely related to either camels or proboscideans.

MacraucheniaWhen they livedMiocene epoch Pliocene epoch Pleistocene epoch

What their world was likeIce Age

BehavioursAdapted to runningSocialherbivoresViviparous

Sabretooths hunt prime plains targets, a herd of Macrauchenia.

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Bird-hipped dinosaurs

Bird-hipped dinosaurs derive their name from the shape of their pelvis, which resembles that of modern birds, whose pubis points to the rear of the animal. Unexpectedly, birds did not evolve from these dinosaurs, but from the lizard-hipped dinosaurs, since this shape of pelvis has evolved more than once. Another distinguishing characteristic of the bird-hipped dinosaurs was a horny beak, which they used to crop plants, much like a horse or deer uses its front teeth today. Duck-billed dinosaurs, horned dinosaurs and armoured dinosaurs were all of the bird-hipped variety.

Scientific name: OrnithischiaRank: OrderCommon names: Bird-hipped

A group of bird-hipped dinosaurs from England during the Lower Cretaceous Period

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Bird-hipped dinosaursOrnithischia or Predentata is an extinct order of beaked, herbivorous dinosaurs. The name ornithischia is derived from the Greek ornitheos (ορνιθειος) meaning 'of a bird' and ischion (ισχιον) meaning 'hip joint'. They are known as the 'bird-hipped' dinosaurs because of their bird-like hip structure, even though birds actually descended from the 'lizard-hipped' dinosaurs (the saurischians). Being herbivores that sometimes lived in herds, they were more numerous than the saurischians. They were prey animals for the theropods and were smaller than the sauropods.

BehavioursHerbivoresEgg layer

When they livedTriassic period Jurassic period Cretaceous period

What killed themThe Cretaceous-Tertiary mass extinction

Explore this groupCeropod DinosaursArmoured Dinosaurs

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Armoured dinosaurs

While early armoured dinosaurs had bony scutes like crocodiles, later forms took armour to the extremes, evolving large plates, spikes, clubs and carapaces. Covering yourself in heavy armour proved to be a very successful anti-predation strategy, as armoured dinosaurs evolved during the early Jurassic and lasted right up until the mass extinction at the end of the Cretaceous period. Though there were many variations and modifications within each type, they came in two basic forms: the stegosaurs with their rows of spikes or plates along the spine, and the more heavily amoured ankylosaurs.

Scientific name: ThyreophoraRank: SuborderCommon names: shield bearers

Wuerhosaurus adult and young by a pool

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The Thyreophora ("shield bearers", often known simply as "armored dinosaurs" - Greek: θυρεος, a large oblong shield, like a door and φορεω, I carry) were a subgroup of the ornithischian dinosaurs. They were armored herbivorous dinosaurs, living from the early Jurassic until the end of the Cretaceous.Thyreophorans are characterized by the presence of body armor lined up in longitudinal rows along the body. Primitive forms had simple, low, keeled scutes or osteoderms whereas more derived forms developed more elaborate structures including spikes and plates. Most thyreophorans had relatively small brains for their body size.Thyreophorans include well-known suborders such as the Ankylosauria and Stegosauria as well as lesser-known groups. Among the Ankylosauria, the two main groups are the Ankylosaurids and Nodosaurids. In both groups, the forelimbs were much shorter than the hindlimbs, and this was particularly exaggerated in stegosaurs. The clade has been defined as the group consisting of all species more closely related to Ankylosaurus than to Triceratops. Thyreophora is the sister group of the Cerapoda within the Genasauria. Ankylosaurids are noted by the presence of a large tail club composed of distended vertebrae that have fused into a single mass. They were heavy-set and heavily armored from head to tail in bony armor, even down to minor features such as the eyelids. Spikes and nodules, often of horn, were set into the armor. The head was flat, stocky, with little or no "neck", roughly shovel-shaped and characterized by two spikes on either side of the head approximately where the ears and cheeks were. Euoplocephalus tutus is perhaps the best-known ankylosaurid.Nodosaurids, the other family in the Ankylosauria, may actually include the ancestors of the ankylosaurids. They lived during the middle Jurassic (approx 170 mya) on up through the late Cretaceous (65 mya) and, while armored as the ankylosaurids, did not have a tail club. Instead, the bony bumps and spikes that covered the rest of their body continued out to the tail and/or were augmented with sharp spines. Two examples of nodosaurs are Sauropelta and Edmontonia, the latter most notable for its formidable forward-pointing shoulder spikes. The Stegosauria suborder comprises the Stegosauridae and Huayangosauridae. These dinosaurs lived mostly from the Middle to Late Jurassic, although some fossils have been found in the Early Cretaceous. Stegosaurs had very small heads with simple, leaf-like teeth. Stegosaurs possessed rows of plates and/or spikes running down the dorsal midline and elongated dorsal vertebra. It has been suggested that stegosaur plates functioned in control of body temperature (thermoregulation) and/or were used as a display to identify members of a species, as well as to attract mates and intimidate rivals. Well known stegosaurs are Stegosaurus and Kentrosaurus.

Armoured dinosaurs

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Stegosaurus

Although nowhere near the largest of the Jurassic dinosaurs, Stegosaurus were still about the size of a bus. Distinctive and heavily built, they were herbivores with short forelimbs and would have walked with their small head close to the ground and the four-spiked tail held high. The double row of plates running along the back helped control body temperature and were probably used in display or possibly in defence against carnivorous Allosaurs. Most fossils for the three known species, including some complete skeletons, have come from the USA, although a recent discovery in Portugal suggests a wider distribution.

Scientific name: StegosaurusRank: GenusCommon names: roof-lizard

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Stegosaurus is a genus of stegosaurid armored dinosaur from the Late Jurassic period (Kimmeridgian to early Tithonian) in what is now western North America. In 2006, a specimen of Stegosaurus was announced from Portugal, showing that they were present in Europe as well. Due to its distinctive tail spikes and plates, Stegosaurus is one of the most recognizable dinosaurs, along with Tyrannosaurus, Triceratops, and Apatosaurus. The name Stegosaurus means "roof lizard" (sometimes put as "covered lizard", but in the sense that a roof covers a building) and is derived from the Greek στέγος-, stegos- ("roof") and σαῦρος, -sauros ("lizard"). At least three species have been identified in the upper Morrison Formation and are known from the remains of about 80 individuals. They lived some 155 to 150 million years ago, in an environment and time dominated by the giant sauropods Diplodocus, Camarasaurus, and Apatosaurus.A large, heavily built, herbivorous quadruped, Stegosaurus had a distinctive and unusual posture, with a heavily rounded back, short forelimbs, head held low to the ground and a stiffened tail held high in the air. Its array of plates and spikes has been the subject of much speculation. The spikes were most likely used for defense, while the plates have also been proposed as a defensive mechanism, as well as having display and thermoregulatory (heat control) functions. Stegosaurus was the largest of all the stegosaurians (bigger than genera such as Kentrosaurus and Huayangosaurus) and, although roughly bus-sized, it nonetheless shared many anatomical features (including the tail spines and plates) with the other stegosaurian genera.

Stegosaurus

Stegosaurus size

BehavioursHeat tolerantPredation defenseHerbivoresEgg layerSocial

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Tarbosaurus

Tarbosaurus was a relative of Tyrannosaurus and lived in Asia during the late Cretaceous. It has the smallest forearms of all the tyrannosaurs known and though slightly smaller than T-rex, was still one of the larger members of the tyrannosaurid family. It had a lightweight skeleton, which probably helped to increase its agility. Tarbosaurus bataar skeletons are common in the rocks of the Nemegt Formation of the Gobi Desert in Mongolia

Scientific name: TarbosaurusRank: GenusCommon names: alarming lizard

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Tarbosaurus is a genus of tyrannosaurid theropod dinosaur that flourished in Asia about 70 million years ago, at the end of the Late Cretaceous Period. Fossils have been recovered in Mongolia, with more fragmentary remains found further afield in parts of China. Although many species have been named, modern paleontologists recognize only one, T. bataar, as valid. Some experts contend that this species is actually an Asian representative of the North American genus Tyrannosaurus; if true, this would invalidate the genus Tarbosaurus altogether.Tarbosaurus and Tyrannosaurus are considered to be at least closely related genera, if not synonymous. Alioramus, also from Mongolia, is thought by some authorities to be the closest relative of Tarbosaurus. Like most known tyrannosaurids, Tarbosaurus was a large bipedal predator, weighing more than a ton and equipped with dozens of large, sharp teeth. It had a unique locking mechanism in its lower jaw and the smallest forelimbs relative to body size of all tyrannosaurids, renowned for their disproportionately tiny, two-fingered forelimbs.Tarbosaurus lived in a humid floodplain criss-crossed by river channels. In this environment, it was an apex predator at the top of the food chain, probably preying on other large dinosaurs like the hadrosaur Saurolophus or the sauropod Nemegtosaurus. Tarbosaurus is very well represented in the fossil record, known from dozens of specimens, including several complete skulls and skeletons. These remains have allowed scientific studies focusing on its phylogeny, skull mechanics, and brain structure.

Tarbosaurus BehavioursScavengerCarnivorousEgg layerPredatorAdapted to running

A recreated encounter between Tarbosaurus and a tail-clubbing Ankylosaur.

Tarbosaurus and a Therizinosaurus face off in a battle of gigantic proportions

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Theropod dinosaurs

Theropod dinosaurs were the top predators in the Jurassic and Cretaceous periods. For over 100 million years theropods were the only large carnivores on land and included all the infamous carnivorous dinosaurs - Tyrannosaurus, Velociraptor and Spinosaurus. However, not all theropods were predators. Some evolved away from their carnivorous origins to consume an omnivorous or herbivorous diet. Birds are the only living descendants of the theropods.

Scientific name: TheropodaRank: SuborderCommon names: beast-footed

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Theropods is both a suborder of bipedal saurischian dinosaurs, and a clade consisting of that suborder and its descendants (including modern birds). Dinosaurs belonging to the suborder theropoda were primarily carnivorous, although a number of theropod groups evolved herbivory, omnivory, and insectivory. Theropods first appeared during the Carnian age of the late Triassic period about 230 million years ago (Ma) and included the sole large terrestrial carnivores from the Early Jurassic until at least the close of the Cretaceous, about 65 Ma. In the Jurassic, birds evolved from small specialized coelurosaurian theropods, and are today represented by 9,900 living species.Among the features linking theropod dinosaurs to birds are the three-toed foot, a furcula (wishbone), air-filled bones and (in some cases) feathers and brooding of the eggs.

Theropod dinosaurs What killed themThe Cretaceous-Tertiary mass extinction

Fossil typesTrace fossils

When they livedTriassic period Jurassic period Cretaceous period

Allosaurus Australovenator Tyrannosaurs

Carcharodontosaurids Dromaeosaurs Coelophysis

Therizinosaurus

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Tyrannosaurs

The family of tyrannosaurs includes the famous Tyrannosaurus rex as well as other large carnivores such as Albertosaurus and Tarbosaurus. They evolved in the late Cretaceous and their large size made them the top predators of the time. Like human beings, tyrannosaurs went through an adolescent growth spurt, increasing greatly in height and weight until they approached sexual maturity. Thereafter they grew much more slowly until they reached their final size. Tyrannosaur fossils are found in Asia and North America, through their ancestors also lived in Europe.

Scientific name: TyrannosauridaeRank: FamilyCommon names: tyrant lizards

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Tyrannosauridae (or tyrannosaurids, meaning "tyrant lizards") is a family of coelurosaurian theropod dinosaurs which comprises two subfamilies containing up to six genera, including the eponymous Tyrannosaurus. The exact number of genera is controversial, with some experts recognizing as few as three. All of these animals lived near the end of the Cretaceous Period and their fossils have been found only in North America and Asia.Although descended from smaller ancestors, tyrannosaurids were almost always the largest predators in their respective ecosystems, putting them at the apex of the food chain. The largest species was Tyrannosaurus rex, one of the largest known land predators, which measured up to 13 metres (43 ft) in length and up to 6.8 tonnes (7.5 short tons) in weight. Tyrannosaurids were bipedal carnivores with massive skulls filled with large teeth. Despite their large size, their legs were long and proportioned for fast movement. In contrast, their arms were very small, bearing only two functional digits.Unlike most other groups of dinosaurs, very complete remains have been discovered for most known tyrannosaurids. This has allowed a variety of research into their biology. Scientific studies have focused on their ontogeny, biomechanics and ecology, among other subjects. Soft tissue, both fossilized and intact, has been reported from one specimen of Tyrannosaurus rex.

Tyrannosaurs Tyrannosaurus rex

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