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The Dinosaur Timeline

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The history of the planet Earth is divided into a bunch of time chunks so whether you’re looking at a time which existed 100 years ago or even as far back as 1000 million years ago you’ll need to know the historian lingo used to classify each of these sizable time periods. The most important of these are aeons, eras and periods.

The Age Of The Dinosaurs

The Dinosaurs and many of the other large prehistoric reptiles existed in the Mesozoic era of the Phanerozoic aeon. The Mesozoic era ran from about 250 million years ago to 65 million years ago. Thats 185 million years of Dinosaur domination, no wonder the Mesozoic era was commonly referred to as the age of the Dinosaurs.

The Mesozoic era contained three periods known as the Triassic, Jurassic and Cretaceous periods. Over the next few sections we will try to cover the key charcterstics of each period to give you an overall understanding of when and where certain dinosaurs existed as well as smashing some of the myths and common misconceptions held by people.

Dinosaur Timeline

The Triassic Period

The Triassic Period is the first phase of the Mesozoic era and spanned for an interval of 35 million years from 250-205 million years ago. Planet Earth was a very different place back then with the most common difference being that all the continents were united to form one huge land mass or super continent known as Pangaea meaning “all lands”.

There were rifts that developed between North America and the African portion of Gondwanaland. This time, the Earth’s crust was stretched, the large blocks subsided and created physiographic basins that deposited thick bed of red-stained sandstone, siltstone and shale.

In the beginning of the Triassic period there was a high percentage of extinction of species that was ever recorded. At this time about 95% became extinct.The direct cause has baffled scientist and is not known but some explanations to this are the effects of the movement by the earth, since the world at this time was cold and there were plenty of volcanic eruptions with poisonous gases. But during this period, new life forms of different species appeared as the others became extinct.

The Plant Life during the Period

In the plant world, the terrain was dominated by the evergreen trees. Mostly are conifers and ginkgoes. The cycads and scale tree became plenty but not as numerous as the evergreen. Numerous plants like the lycophytes and glossopterids appeared. The seed plants dominated the terrestrial. In the northern hemisphere area, conifers flourished.

In the southern hemisphere, a seed fern called glossopteris was dominant during the early Triassic stage. The general climate was very hot and dry, much similar to the desert-like conditions that we have now. The world all over was hot and there was no evidence of ice sheets on the poles. This particular climate is most suitable for reptiles. However, seasonal heavy rains occur. During the wet season, major lakes and rivers began to form. And the Polar region became moist and mild.

The Dinosaurs during the Period

At the start of this period, dinosaurs still did not exist. However there were many reptiles and amphibians that roamed the earth during this time. Some corals have appeared in the seas and the ammonites reappeared. At this point plants were mostly conifers and seed plants. The first mammals appeared during the late Triassic period, they were tiny and mostly they were nocturnal which means they are only active at night. Now frogs, turtles, salamanders, snakes and lizards appeared. But still Dinosaurs were smaller then. Flying reptiles such as the Pterosaurs appeared in this period and also some marine reptiles. Be reminded though that flying reptiles does not belong to the group of dinosaurs.

They just lived during the time when the dinosaurs started to exist. The Pterosaurs do not have feathers and their wings are similar to a bat. They were the first flying vertebrates. Other important reptiles that were present were the ichthyosaurs and plesiosaurs. The ichthyosaurs are marine reptiles with long snout and their bodies shaped like the modern dolphins. The Plesiosaurs on the other hand had broad turtle-like bodies, long necks and tails, and large flippers. The following Dinosaurs although smaller in size are worth mentioning since they were the first to characterize the Triassic Period. Here they are: o Coelophysis o Eoraptor o Plateosaurus



The Coelophysis was a small meat-eating dinosaur that lived in the late Triassic Period. The Coelophysis was a slender, graceful, and fast predator. It had a long jaw that has curved dagger-like teeth. Its length was about 3 m (10 ft) and can run on two or four legs.

It inhabited the highland forest areas. Most meat-eaters travel alone or in small groups not like the plant-eaters that live and travel together. Some young Coelophysis remains were found in the ribcages of two adult Coelophysis. This was once thought to be evidence of a live birth rather than egg laying.

However the advanced development of the skeletons indicated that the young Coelophysis were probably eaten by the adults. Therefore cannibalism also occurred in living meat-eaters, especially when food is scarce.

The Eoraptor

The Eoraptor was a dinosaur that is about the size of an average modern dog that lived also during the later part of the Triassic Period. The Eoraptor was excavated in 1992 at the Northwestern part of Argentina, what they unearthed was the skull and skeleton that was about 3 ft. long. The Eoraptor had very sharp teeth, probably stood on both three-toed feet and had three-fingered hands. Like the Coelophysis, it is evident that it was a part of the suborder Theropoda or the “meat-eating dinosaurs”.

The Plateosaurus

The Plateosaurus, the largest dinosaur in its time, was a well known prosauropod or an herbivorous kind of Dinosaur. Like most dinosaurs, the Plateosaurus had a heavy, sturdy limb, its tail was made up half its length and its size was about 8 meters long. They had small skull and spoon-shaped head that was stronger than most prosauropods.

Their necks were long and slender that could look easily on bushes and trees. They can walk in four legs and can rear up on its hind legs to search the higher levels and gain access in higher foliage. The Plateosaurus lived around the area of France, Germany and Switzerland.

When the Triassic Period was about to end, mass extinction happened. The Pangaea or the land mass started to break apart and was divided into two, namely the Laurasia in the north and Gondwanaland in the south. The Antarctica belongs to the Gondwanaland continent and it was united with South America, India, Africa and Australia.

Mass Extinction

The two continents still continued to drift apart into smaller continents. Scientists called this movement as the “continental drift” as we know it today. When the Pangaea drifted apart, many huge volcano eruptions happened, due to this violent natural disaster, many animal species died.

Mostly, small primitive dinosaurs became extinct. The rest of the dinosaurs that survived further evolved during the Jurassic period.Take note that the Dinosaurs were really dominant during Jurassic and Cretaceous period than the Triassic period. Major extinction happened both at the beginning and at the end of the Triassic Period. The rise of the dinosaurs was characterized in the Triassic Period but it was until later that really big and famous. Dinosaurs came to be.

The Jurassic Period

The Jurassic Period was the second phase of the Mesozoic Era. The time scale for this famous period is from 205 to 138 MYA (million years ago). This period was named after the Jura Mountains because of the exposure and discovery of the marine lime stones.

This mountain is located in the region that unites Switzerland, France and Germany. In the early part of the Jurassic Period, the huge continent Pangaea or the continental land mass was in the process of drifting apart. It formed the beginning of a new world. Huge volcanic eruptions were commonplace which spitted out rivers of lava and it also spread clouds of poisonous gases.

In this early part, Greece, Italy, Iran and Turkey as we know it today were connected to Gondwanaland or the part of the super continent or Pangaea that begun to drift apart in the Triassic Period. Antarctica and Australia were already detached from Gondwanaland but both of them remained to be connected together.

Meanwhile, South America and Africa started to break apart. A long and narrow seaway moved northward in between the two continents, then it eventually joined the great equatorial sea that was called Tethys. As the seaways met and grew, warm, shallow marine water has spread more over in Europe.

Other landmasses bordered the Tethys Sea. As the Jurassic period came to its end, the shallow seas started to drain away and thick limestone beds were left in regions where the oil and gas were abundant.

The Plant Life during the Period

In this period, the vegetation was much greener compared to the Triassic period. The Jurassic weather condition was warm and dampness was provided by the early ocean. The Subtropical forests largely consisted of the gymnosperms like the cycads and conifer, ginkgoes and seed ferns.

It is interesting to note that at present time, these plants still exists. In the middle part of the Jurassic period, the Angiosperms (flowering plants) appeared. Because the climate during the Jurassic period varied a lot, some major forests grew that fed a lot of herbivores.

The Dinosaurs during the Period

The Jurassic Period was called the “Age of the Ruling Reptiles”. Huge dinosaurs were the dominant species. They ruled the land because of their size and were the largest among the land animals. There were a variety of dinosaurs like the herbivores and the carnivores in the Jurassic period and their features were different from each other.

The herbivores became much bigger which became an advantage to them because they could reach their food on tall trees. The carnivores also were larger and they were much fiercer in dealing with huge prey. Some flying reptiles were visible in the sky and the earliest birds like the Pterosaurs and Archaeopteryx existed. Many marine reptiles came in this period like the plesiosaurs, ichthyosaurs, crocodiles, sharks and rays. It was during the Late Jurassic stage, that huge dinosaurs like the Stegosaurus, Brachiosaurus, Ceratosaurus, and Allosaurus existed.

The Brachiosaurus

The Brachiosaurus was a land dweller and could eat on tall foliage. Its forelegs were longer than its back. It had a length of 24 meters long and was about 12.6 meters tall.

The Diplodocus

The Diplodocus lived in the United States. It was a four legged dinosaur that had a long neck, short body and a long tail. It stood up to 87 feet and had a slender and less bulky body than the Apatosaurus. It was a vegetarian dinosaur with a small head and slender teeth that grazed in shallow water and marshes.

The Stegosaurus

The Stegosaurus was also a plant-eating dinosaur which was known for its large triangular plates along the crest of its back to keep its body warm. These plates, as well as a number of spikes on the tail made the Stegosaurus one of the most well known of all dinosaurs.

The Apatosaurus

The Apatosaurus or formerly known as Brontosaurus was a large plant eating dinosaur. It lived during the late phase of the Jurassic Period for about 150 million years ago. This long-necked dinosaur was the largest dinosaur that lived on land. It had a small head, a long slender neck, and a long tail that was almost one and one-half times longer than the rest of the body.

The Apatosaurus also had an elongated skull with short, pointed teeth. Its nostrils were located high on its head, directly above and in front of the eyes.

The Allosaurus

The Allosaurus was a carnivorous dinosaur which was dominant around 150 million years ago during the Late Jurassic period. These lizard-hipped dinosaurs could reach up to 12 m (40 ft) in length and can stand 15 ft tall. The Allosaurus had big hind legs which were similar to a bird’s foot with three forward toes and one backward hoof like toe, its heavy tail aided balance while walking.

This creature had a very large jaw with its equally large head (1 m/3 ft long). To have its fill of meat, the Allosaurus had sharp serrated teeth for biting and tearing meaty flesh effectively.

The Archaeopteryx

Archaeopteryx was a small, feathered dinosaur. It was about as large as a crow but lacked a beak and had a more slender chest area than do modern birds. It had claws on its wingtips, and its tail feathers were supported by a long bony tail rather than by long quills, as in modern birds. The archaeopteryx fed on insects rather than seeds. It found shelter in trees.

The Ozraptor

The Ozraptor was a 3 meter long carnivore. It could move on its two legs and had a tail that was stiff and three-fingered hands.

The Rhoetosaurus

The Rhoetosaurus was a dinosaur from the mid-Jurassic period. It used its four legs for walking and had a long neck and tail. Its head was small and its body was massive. The Rhoetosaurus was about 12 meters long.

The Rhamphorhynchus

The Rhamphorhynchus or pterosaur lived in Europe and Africa during the late Jurassic Period. The Rhamphorhynchus were not really dinosaurs but were only relatives. There were two types of pterosaurs during the Jurassic Period. One was the long-tailed group and the other a short-tailed group. They belonged to the long-tailed type. Its long tail was stiff with a kite-shaped flap.

The Cretaceous Period

The Cretaceous Period was the last period of the Mesozoic era and marked the end of the dinosaurs. It spanned a time from 138 million to about 65 MYA (million years ago). In this period the continents separated. However, Australia and Antarctica were still united. There were important things that happened in this period such as the development of flowering plants like the magnolias and water lilies and the increase in the number of different kinds of insects.

This was the beginning of the modern insects such as the ants, butterflies, grasshoppers, termites and aphids. During the Late Cretaceous period, the sea levels rose all over the world resulting to the submerging of one-third of the earth’s land area. This caused the heat from the sun to be distributed pole ward by the ocean currents which produced a warm, mild worldwide climate with ice-free poles. Such climate made cold-blooded reptiles exist even in the northern latitudes. The Scientists of today believed that there was a giant meteor that hit the earth 65 million years ago.

This caused massive destruction and brought acid rain, tidal waves, and clouds of dust which blocked the rays of the sun and lowered temperatures all over the world. The vegetation was devastated which affected the food source of the small animals in which the bigger reptiles were depending on food for also. The five great reptilian groups: dinosaurs, ichthyosaurs, pterosaurs, and plesiosaurs became extinct due to this climate change. Others survived like the birds, mammals, small reptiles, and marine creatures and plants.

The Plant Life during the Period

The cycads and fossil ferns that were found in Cretaceous rocks in the Arctic latitudes were similar to the plants in subtropical rain forests that are now growing today. It is in this period that the flora took a modern appearance which is similar to many of today’s generation of trees, like the oak, maple, and beech. Despite of the mild conditions, lots of faunal extinctions happened towards the end of the period due to the rapid climate change which occurred during this period.

The Dinosaurs during the Period

In the Cretaceous period, dinosaurs became much more dominant than the two early periods of the Mesozoic era. It was during this time that the Centrosaurus and Triceratops appeared, they are often called the horned dinosaurs. The duckbilled Parasaurolophus, the armored Ankylosaurus, and the large, fierce carnivore Tyrannosaurus Rex also appeared in this period. Those were the few of the evolving dinosaurs during this distinct period.

The dinosaurs from smaller ones to larger ones lived in forests of cycads, ferns and conifers. Great marine reptiles were visible in the seas and flying reptiles can be seen in the skies.Despite the evolution of new life forms all of them became extinct at the end of this period.

The Triceratops

The Triceratops belonged to the quadrupe herbivore dinosaur which lived during Cretaceous Period and populated in North America and in Asia 65 million years ago. It also belonged to the group of ornithischian which means a “bird-hipped”) dinosaur that is called ceratopsians (“ a horned face dinosaur”). The adult Triceratops stood at about 8 meters (26 feet) long and weighed about 12 metric tons. The skulls of the adult triceratops were around 8 feet long.

They had a narrow and birdlike beak. The Triceratops was one among the biggest horned dinosaurs. It had three big horns on the skull – one on the snout and the other one on top of each eye. At the underside of their neck frill, there is a very thick network of blood vessels. Its fossils of today indicated that the heat was radiated in the frill passing through the blood vessels, same way as the elephants carry the blood towards their ears to radiate heat. Scientists do know that the Triceratops gallops same as the rhinoceros, but others would say that the dinosaur was too clumsy and heavy for this. To gather food, its jaws open sideways. When they gathered the food, they would rotate their head and chop their food using its powerful jaws.

The Ankylosaurus

The Ankylosaurus was a plant-eating dinosaur found in North America during the late Cretaceous Period, which ended about 65 million years ago. The Ankylosaurus was one of the last of the heavily armored ankylosaurs, a group of medium-sized ornithischian (bird-hipped) dinosaurs. It grew to 10 meters (33 feet) in length and walked on four legs. They had a broad, low body covered with protective bony armor and spines. Its tail ended in a club made of fused bone embedded in a leathery hide which they wielded as a weapon to fight off predators.

The Tyrannosaurus Rex

The Tyrannosaurus Rex was a meat-eating dinosaur which became visible during the late stage of the Cretaceous Period about 65 million years ago. The Tyrannosaurus name came from a Greek word “tyrannos” which means “tyrant”, and “sauros”, that means “lizard”. These dinosaurs were easily recognized because of their large size, its upright posture, jagged teeth, and two-fingered forelimbs. They were one of the largest carnivore animals that existed.

They reached 12.5 m (41 ft) in length and can stand 16 feet. The head of Tyrannosaurus was big, flexible and contained of a brain similar to the size of the modern reptiles. Tyrannosaurus was probably much more powerful than any other meat-eating dinosaur. At the bridge of its nose, there were wart-like knobs. The Tyrannosaurus had arms that were short and had small amount of nerves passing through it. The development of this nerve made the movements of its arms clumsy and unwieldy. Its stout chest indicated that its lungs were very big.

The interwoven bones protected its stomach and the rest of the internal organs. Its legs were slender and long. Scientists have recovered dozens of skeletons of this large saurischian (had hip structure similar to that of Lizards) around western part of US and Canada and perhaps they know more about this dinosaur than the other predatory dinosaur.

Dinosaur Timeline

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