Natural History And Fossils

The Story Of Life On Planet Earth

What Are Dinosaurs?

Dinosaurs are reptiles that grew to massive sizes! Dinosaurs were cold blooded (some were warm blooded). A dinosaur can only: 1. live on land, not in the sea or sky 2. have legs directly under their body not to the side like crocodiles and lizards 3. live in the Mesozoic era. The majority of dinosaurs are herbivores while the rest are carnivores. The Mesozoic era is divided into 3 periods. The first being the Triassic which went from 248 million years ago to 206 million years ago. The second period was the Jurassic which went from 206 million years ago to 144 million years ago. The last period was the Cretaceous which went from 144 million years ago to 65 million years ago. In total dinosaurs ruled the earth for 160 million years (dinosaurs did not rule the earth at the start of the Triassic).

Triassic Dinosaurs

At the start of the Triassic era dinosaurs did not rule. The world was ruled by a crocodile like creature called Chasmatosaurus. Chasmatosaurus grew to 3.5 m and was the largest creature on earth at that time! ( a mass extinction had occurred not long before). Chasmatosaurus fed on a creature called Lystrosaurus. Lystrosaurus was like a dinosaur but not quite, it was half reptile, half mammal. Chasmatosaurus had long legs for a crocodile so it could run and hunt on land and in the water. At the late Triassic Lystrosaurus and Chasmatosaurus died out and the few scattered dinosaurs that evolved took over. Among the first dinosaurs was the little predator called Eoraptor which means "the dawn stealer". Eoraptor hunted insects and small mammals. Then came Coelophysis. Coelophysis was a predator that was extremely fast and agile, Coelophysis could chase down flying insects and catch them in the air. At the time of Coelophysis a large early crocodile was present called Rudiodon. Being Agile meant that Coelophysis could dodge the jaws of the Rudiodon. At the very end of the Triassic a large sauropod called Plateosaurus evolved. Plateosaurus was too large for an individual Coelophysis to kill but occasionally Coelophysis would group together to attack larger dinosaurs so Plateosaurus better watch out!

Jurassic Dinosaurs

At the start of the Jurassic dinosaurs start to get bigger! The largest Jurassic dinosaurs were the sauropods. All sauropods were distinguished by their long neck. Brachiosaurus had a neck pointing up, high in the treetops. Brachiosaurus could feed on the tops of the trees that no other dinosaurs could reach. Brachiosaurus's neck would have been really stiff and not very flexible. Brachiosaurus grew to about 25m in length! Another type of Jurassic sauropod was Diplodocus. Diplodocus's neck was much different to that of Brachiosaurus, Diplodocus's neck was horizontal to its body. Having a horizontal neck meant that Diplodocus could not feed on the tops of the trees but the low shrubs and bushes on the ground. Diplodocus grew to 28m in length! Sauropods were not the only large creatures around. A dinosaur called stegosaurus had plates on its back and 4 spikes on its tail for defense. Stegosaurus fed on bushes low to the ground like Diplodocus. When Stegosaurus was threatened my an attacker it would flush blood into its plates and make them stand out bright red to scare off its attacker. Among the biggest predators of the Jurassic was Ceratosaurus. Ceratosaurus grew to about 8m in length and could hunt down most of the small Jurassic herbivores such as Dryosaurus. Ceratosaurus was not the biggest Jurassic killer, that title belongs to Allosaurus. Allosaurus was just as big as Tyrannosaurus Rex and just as deadly. This massive 12m killer could bring down the armoured Stegosaurus and even some of the giant sauropods. Allosaurus was the biggest killer of the Mesozoic era so far but even larger carnivores than Allosaurus would evolve in the Cretaceous period.

Cretaceous Dinosaurs

During the Cretaceous period dinosaurs got very big! Larger herbivores evolved. To keep up with the herbivores the carnivores also got bigger ( and smarter). According to scientists the smartest dinosaur was Troodon. Troodon was a small carnivore with a big brain compared to its body size. Troodon hunted small dinosaurs and mammals but Troodon was prey for even larger carnivores. The herbivores didn't get much smarter but they evolved a defense, they lived in herds such as the Hadrosaurs. Hadrosaurs were a successful group of dinosaurs that had duck bills and could make loud trumpeting sounds. If a carnivore attacked, the whole herd would soon know about it. In the Cretaceous many herbivores evolved strange features on their heads or body, mainly for defense such as Styracosaurus which was a Ceratopsion who evolved spikes coming off of its head. Ceratopsions were a successful group of horned dinosaurs. The most famous Ceratopsion was Triceratops. New fossil evidence suggests that Triceratops lived in herds. Triceratops was armed with two 1 meter spikes to gore its attacker and would have been more than a match for Tyrannosaurus Rex. Cretaceous Sauropods were not as common or as big as they were in the Jurassic. Saltasaurus was a Sauropod that grew to about 12m. Saltasaurus had bony plates on its back for defense. The most armoured of the dinosaurs were definately the Ankylosaurs. Ankylosaurs were covered in armour, a predator would break its teeth if it bite into one. The biggest Ankylosaur was Ankylosaurus which grew to 12m in length. Ankylosaurus had a bony club on the end of its tail, if a predator came it would swing its bony club into the attacker which would have crippled the predator and broken bones. The predators of the Cretaceous got even more vicious. A group of carnivores called the Dromeosaurs evolved. Dromeosaurs were equipped with large slashing claws on each foot. The Dromeosaur would leap onto the back of its victim and rake it with its claws, tearing it apart. Lots of Dromeosaurs evolved such as Megaraptor, Utahraptor, Dromeosaurus, Dienonychus and of coarse the small but deadly Velociraptor. The larger carnivores were even more frightening. Spinosaurus was a large Therapod that had a sail on its back. Scientists have debated on what the sail was used for, most say its for display but some say it was used to absorb heat. Spinosaurus had a long pointed snout suggesting it was a fish eater not a flesh eater, being a fish eater it would not have been very strong and easily defeated in a fight with another predator. Spinosaurus came from north africa along with another large carnivore, Charcharodontosaurus. Charcharodontosaurus was a massive flesh eater that hunted the largest dinosaurs. At around 14m in length it could hunt and kill Spinosaurus. Charcharodontosaurus means shark toothed lizard for its razor sharp teeth (like a sharks). Charcharodontosaurus was one of the largest predatory dinosaurs ever but the largest was Giganotosaurus. Giganotosaurus grew to 16m in length! It hunted the largest Sauropod ever Argentinosaurus. Giganotosaurus was 4m longer than t-rex and had larger teeth as well. Then of coarse there was Tyrannosaurus Rex. T-rex is probably the most famous dinosaur ever. T-rex had stronger jaws than any other carnivore, it could crush its victims bones. T-rex has been the star of many movies such as Jurassic Park (1999). A. The dinosaurs of the Cretaceous were the most weird and vicious yet by far.

Extinction Of The Dinosaurs

Many scientists debate about what happened to the dinosaurs. Theory 1 is that climate change effected the plants that herbivores fed on, when the herbivores died out so did the carnivores who fed on the herbivores. Theory 2 is that volcanic activity poisoned the atmosphere and all the plants and animals died due to poor living conditions and poisoned air. The most popular theory is that an asteroid about 10 kilometers wide smashed into the Gulf Of Mexico and wiped them all out with a massive shock wave caused by the collision. Any dinosaurs that survived the shock wave would die of starvation because the impact threw tonnes of dirt and rock into the sky, blocking out the sun. For millions of years the earth was black and dark. Only when sunlight re appeared did life continue on but by then the dinosaurs were all dead.

My Favorite Dinosaur - Velociraptor

Velociraptor was a small carnivorous dinosaur that grew to 1.8m in length. Being small was a downside but Velociraptor lived in packs so it could gang up on larger dinosaurs. One of Velociraptor's favorite prey was a small Ceratopsion called Protoceratops. A fossil of a Velociraptor and a Protoceratops locked in mortal combat has been found, the Protoceratops grips the raptors arm in its powerful beak while the Velociraptor has it's large claw on the Protoceratops's throat. Velociraptor's claw on its toe was massive, much larger than the other claws. It needed this weapon because its teeth were very small and delicate so it could not hold onto struggling prey in its jaws but pierced the throat with its claw. Velociraptor's fossils have been found in the Gobi Desert in Mongolia. Although Velociraptor was small it packed a punch!

Image- Velociraptor