The Cretaceous Period was the last phase of the Mesozoic era and spanned for an interval of 75 million years from 135-65 million years ago. Although the dinosaurs died out in this period many interesting dinosaurs like the Tyrannosaurus Rex and the Triceratops appeared making this period quite interesting.

Other important things that happened during the cretaceous included further splitting of the pangea breaking it down even further into the smaller continents we recognise today.

The cretaceous also denoted a start in the appearance of flowering plants like magnolias and water lilies as well as many of the modern insects we know of today. Examples include ants, butterflies, grasshoppers, termites and aphids. All of the above meant that the cretaceous truly was a an amazing and diverse period for life on the planet earth, sadly it was also the end of the dinosaurs but with over 180 million years of domination I don’t think they can complain.

More Pangea Splitting

Ever since Laurasia split from Gondwana in the jurassic further splits and rifts within these 2 lesser continents continued to happen during the cretaceous.Gondwana finally split into four smaller pieces namely Africa, South America, India and Antarctica/Australia whilst Laurasia was still moving further away into the northern hemisphere.

This splitting of the Earths major land masses would continue well on into the Cenozoic era even after the dinosaurs had become extinct until it would finally resemble what we see on modern day maps. Remember these rifts are still happening today and maybe in millions of years from now the landscape of the earth will change once again.

High Ocean Levels

During the cretaceous period the sea levels rose all over the world resulting in the submerging of at least one third of the earth’s land area. Why there was so much water can be attributed to three possible reasons.

• There were no frozen poles during the cretaceous (or jurassic), this reason alone meant that water levels were generally higher during the Mesozoic era.
• In general because of the higher temperatures that existed during this time a thermal expansion of the ocean waters meant a greater volume for the same mass of water. If we look at the temperatures on the ocean bed today they are close to 3-4 degrees centigrade whereas during the cretaceous they would have been as high as 15 degrees centigrade which demonstrates a real difference in overal temperatures.
• Both the jurassic and the cretaceous contained huge levels of volcanic activity thanks to the constant tectonic changes happening within the earth. This meant that much of the oceans surface consisted of erupting volcanoes filling the sea bed with mini mountain ranges thus making the oceans extremely shallow and causing them to contain less water thus flooding much of the earths then low lying land.

General Climate

As far as living species were concerned temperatures were much lower and more importantly stable for most of the cretaceous. Compared to the triassic and jurassic periods better temperatures meant created a much more hospitable environment for animals and plants to diversify.

This massive climate change was mainly due to the changes happening at the tectonic level, the cretaceous was in general a much wetter period with oceans flooding the land to create many lakes, rivers and swamps.

All this extra water offered great opportunities for diversification in both animals and plants, of course the tectonic movements much volcanic activity which as we shall see had a massive impact on temperatures towards the end of the cretaceous period where global warming and a possible asteroid hitting the earth caused the massive dinosaur extinction commonly referred to as the cretaceous tertiary extinction

Cretaceous Plant Life

The biggest change in the cretaceous had to be the appearance and advancement of flowering plants. Until now the dominant plant life consisted of cycads, seed ferns and confiers. The introduction of flowering plants added a totally new dimension to the ecological landscape and by the end of the cretaceous they pretty much took over as the dominiating plant species.

The plant life during the cretaceous took a very modern appearance making the landscape very similar to todays tropical jungles and forests. The angiosperms success and spread during the cretaceous was significant in supporting the birth of many new insect and mammal species. This was truly an exceptional and hugely diverse time for both animals and plants, and one that would start the end of the dinosaurs and the start of new life in the cenozoic era.

Cretaceous Animals

In the Cretaceous period dinosaurs reached the peak of their dominance. It was during this time that the horned dinosaurs like the Centrosaurus and Triceratops appeared. The duckbilled Parasaurolophus, the armored Ankylosaurus, and the well known Tyrannosaurus also made their first appearance during the cretaceous.

Both birds and the flying reptiles such as the pterosaurs were now much more developed and completely dominated the skies.

In the sea ichthyosaurs, plesiosaurs and sharks continued to dominate marine life as they did in much of the jurassic. However new predators namely Mosasaurs who were snake like reptiles also came into existance during this hugely diverse time period. These ferocious creatures lived in lagoon and shallow water areas where they would aggressively ambush passing prey. Other animals that appeared in the cretaceous include large crocodiles, turtles, snakes and lizards.

Dinosaur Extinction

At the end of the cretaceous period a mass extinction second only to the permian triassic extinction wiped out over 80% of all living species on the planet earth. It wasn’t just the dinosaurs that were affected, pterosaurs, mosasaurs, plesiosaurs, ammonites, belemnites and many other species which were common at that time simply dissappeared.

Its not 100% clear what caused the extinction but some key factors which certainly contributed to it include the striking of a massive asteroid approximately 10 kilometres in diameter. This asteroid landed in the Yucatan peninsula in Mexico and would have had disasterous consequences ranging from forest fires to sunlight blocking dust and causing mass darkness and death to both animal and plant life.

Of course there are other theories related to huge volcanic eruptions, global warming and even disease amongst the dinosaurs. Again nothing is confirmed except that the death of the dinosaurs paved the way for a new wave of mammal species which took over and dominated in the Cenozoic era.

The Jurassic Period is the second phase of the Mesozoic era and quite possibly the most interesting. It spanned a total time period of around 65 million years and started around 205 million years ago right up to about 135 million years ago. It was named after the Jura mountains which are located between the border of Switzerland and France for the simple reason that the first rocks of the jurassic period were found and studied there.

A Splitting Super Continent

Although the super continent had started to show signs of splitting in the latter part of the Triassic it didn’t actually split until the middle of the Jurassic period around 180 million years ago. The initial split left 2 continents a northern part called Laurasia (mainly North America and Europe) and a southern part called Gondwana (mainly South America, Africa, Australia).

Throughout the Jurassic and the rest of the Mesozoic era these continents continued to drift apart causing the formation of new oceans and the flooding of many parts of these once arid and super dry central regions. All this extra water meant that deserts and previously uninhabitable regions were slowly turning into swamps and tropical forests which would change the face of the Earth forever.

Jurassic Plant Life

The above mentioned splitting and major break up of the super continent created not only a fresh new tropical environment for the next generation of dinosaurs but one that was greener and richer in plant life. The Jurassic weather was warm and the dampness provided by the early ocean exposure ensured that topical forests and plant life was plentiful.

Forests of ferns, seed ferns, ginkgoes, cycads and conifers were common and the first flowering plants also started to appear later in the Jurassic. This was indeed a fine time for plant life and one that would form the foundation for modern day angiosperms.

Jurassic Animal Life

The Jurassic Period was called the “Age of the Ruling Reptiles”. Unlike the Triassic period, dinosaurs were now much larger which clearly put them at the top of the food chain. These extra large reptiles were the dominating species now and the Jurassic period marked their golden years.

Some of the largest dinosaurs of the Jurassic were the herbivore plant eating sauropods. Thanks to the abundant plant life massive herbivores such as the Brachiosaurus, Diplodocus and Apatosaurus had no shortage of food and enjoyed a level of comfort not previously enjoyed by the Triassic dinosaurs.

Just like the terrestrial herbivores of the Jurassic the carnivores were also a lot larger than their Triassic counterparts. The fiercest of these were extremely large theropods like the Allosaurus and the Ceratosaurus. The Allosaurus was probably the top Jurassic Predator of its time and with the largest specimen coming in at a length of over 9 metres its prey was most likely the large herbivores such as the sauropods. As a quick reminder thanks to movies like Jurassic Park its a common misunderstanding that the Tyrannosaurus Rex also existed during the Jurassic period when in actual fact it came into existance much later in the Cretaceous period. Other dinosaurs that fall under this misconception include the Triceratops who also existed much later in the Cretaceous.

Flying reptiles like the Pterosaurs were still the dominant air species but during the Jurassic we also find the appearance of the first primitive bird like species in the form of the Archaeopteryx. Despite having more in common with dinosaurs than modern day birds it was still the first feathered flying species and clearly an evoloutionary step towards the bird species.

Jurassic marine reptiles consisted mainly of the plesiosaurs, ichthyosaurs, large marine crocodiles, variations of modern day sharks as well as cephalopods which are relatives of todays squid and octupuss species.

More Extinctions

Unlike the Triassic most of the land dinosaurs and reptile families that existed in the latter Jurassic period were also still in existance in the early Cretaceous. So unlike previous periods there were no mass extinction event that denoted the end of the Jurassic 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 c shaped land mass or super continent known as Pangaea meaning “all lands”.

Two Extinctions & The Dinosaurs

This was an interesting time period because on the one hand a single continent allowed for the free movement of animal species from one region to another, hence diversification and change was common but on the other hand it was also the time of the largest mass extinction ever to occur on the planet Earth.

This mass extinction also known as the “Great Dying” accounted for the loss of over 95% of the then existing marine life as well as 70% of the terrestrial life. This wasn’t the extinction of a single species or a group of species but everything from plants, animals, insects, fishes and pretty much most living things were totally wiped out. Some say that up to 99% of the living species of the world were gone in the blink of a prehistoric second.

Note that dinosaurs didn’t actually exist this early in the Triassic so this particular extinction is not to be confused with the second extinction which also occurred in the Triassic but towards its end. As far as dinosaur existance is concerned it was after the first mass extinction that both mammals and dinosaurs came into being but we’ll talk about that later.

The direct cause of the first extinction also known as the Permio-Triassic Extinction has baffled scientists for years and although there is very little evidence to pin point exactly how things ended there are a couple of theories which range from massive volcanic eruptions, to a large asteroid hitting the planet, or even a simple rise in temperatures due to the formation of the super continent. Any one of these events could have totally destroyed the Earths ability to support plant and animal life but we can never be sure.

Triassic Plant Life

The general weather and climate throughout the Triassic was very warm and arid. This was due to the lack of oceanic exposure and meant that the central region was primarily desert so plant life really only survived in the northen and southern hemispheres.

No flowering plants existed at this time so most plant life looked pretty boring as a mix of browns and greens. In general the plant life of the Triassic consisted of cycads, lycophytes (mosses), Glossopterids (seed ferns), Ginkoes as well as other seed plants like conifers.

Triassic Animal Life

Coming into the Triassic the animal life consisted of species that had either survived the Permian-Triassic extinction or had newly appeared after the extinction. This factor alone made it a very interesting time period with many new appearances.

Insects and many other invertibrate species were extremely common and dominant in the Permian period, however only a few of these made it into the Triassic. In fact the Permian contained some of the largest insects ever recorded, sadly most of these did not survive into the Triassic and instead and new form of modern insect evolved.

Other than that Ammonites, Corals, Amphibians and various other specialised invertibrates survived and carried on throughout the Triassic. Reptiles were for the most part the most dominating species of the Triassic but despite this the first mammals also appeared during this time period and were thought to have evolved from the mammal like reptiles (therapsids) that were common in the Permian period.

At this time the reptile scene was really starting to take over Dinosaurs (Land Reptiles), Pterosaurs(Flying Reptiles), Plesiosaurs (Marine Reptiles), Ichthyosaurus (Fish Reptiles) all started appearing. This was a great period for Archosaurs and the various other diapsid reptiles which were slowly taking over from the synapsids of the Permian period.

Other animals of note which also made a first appearance in the Triassic include turtles, frogs, crocodiles, and many types of lizards.

Despite the Triassic being the birth time of the dinosaurs they were still small and didn’t fully develop into the massive land reptiles we imagine them as until the Jurassic period. Some examples of the dinosaurs that made an appearance include:

• Coelophysis
• Eoraptor
• Plateosaurus

The Late Triassic Extinction

When the Triassic Period was about to end another mass extinction not quite as damaging as the first occurred. The worst damage was made to marine life where most marine reptiles except the plesiosaurs and the ichthyosaurs died out.

On the land many of the large archosaur reptiles, labyrinthodont amphibians, Conodonts as well as some of the early dinosaur species all went extinct. This was a huge filteration process with many species completely eradicated from the planet. This however meant that the remaining dinosaurs were left as the largest land animals on the earth which set them up for complete domination into the Jurassic.

Just like most events this far back there is no clear answer as to what caused this extinction. Certainly the super continent although still in one piece had started to split and huge volcanic eruptions have been recorded during this time period. Other theories include a metoer as well as planetary cooling. We really don’t know but what we do know is that whether out of pure luck or sheer genius the dinosaurs were automatically given a clear path to success after this major extinction process.

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 learn the lingo used to classify each of these sizable time periods. The most important of these are aeons, eras and periods.

The rest of this article will go onto explain the timeline that the dinosaurs existed in so if you’re not familiar with the terms aeon, era and period we recommend you take a look at our timeline defintions page here, otherwise read on to learn more about the age of the dinosaurs.

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 common myths and misconceptions surrounding that time period.

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 c shaped land mass or super continent known as Pangaea meaning “all lands”.

More about the Triassic Period.

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.

More about the Jurassic Period.

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 fully 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.

More about the Cretaceous Period.