The Jurassic Period
It is the middle stage of the Mesozoic Era. We are going to know all the information and characteristics of this period.
It begins approximately 200 million years ago, with the separation of Pangea into 2 continents (Laurasia and Gondwana) and a mass extinction that is in a third position of the greatest extinctions and ends 145 million years ago, with the entrance to the Cretaceous.
The entrance to the Cretaceous was due to the extinction of species, not as great as the one that existed in the Paleozoic to Mesozoic passage in the Permian-Triassic transition, or as the one that existed in the Cretaceous, but a series of important and striking species disappeared, enough to determine a change of period.
Lower Jurassic. It begins 200 million years ago and ends 176 million years ago. Great dominance of dinosaurs in the terrestrial environment, almost unaffected by extinction at the end of the Triassic.
Middle Jurassic. It begins 176 million years ago and ends 161 million years ago. There are not many striking data from this stage, but it is thought that at this point the continents of the Southern Hemisphere began to separate from the planet.
Upper Jurassic. It begins 161 million years ago and ends 145 million years ago. The time of maximum apogee of the sauropod giants, where they had more diversification. In addition, ceratopsians and prehistoric birds such as Archaeopteryx begin to appear.
The Jurassic Period is much wetter than the Triassic, deserts are scarce and forests cover practically the entire planet. We can observe two great continents: Laurasia to the north and Gondwana to the south.
Laurasia would be covered by present North America and the Eurasian plate, while Gondwana would be covered by South America, Africa, the Indian peninsula and Antarctica. The separation of the continents was due to the movement of the tectonic plates, a process that continues to affect them today.
We are moving from an arid climate to an even warmer but more humid one, due to the exponential growth of forests all over the planet. This humid climate and increased forest cover allowed for a warm and pleasant environment for almost every living being, which allowed the animals to acquire titanic proportions.
Of the flora, one very important fact is that fossilized pollen has been found from the oldest angiosperm, dating from this period.
Finding this type of fossil is very difficult and a great joy in the field of paleontology, as it allows us to approach the origins of current life forms.
Although the specimen of a well-differentiated angiosperm, its vegetative structure such as leaves and stem, has been dated to the Early Cretaceous. Therefore, there is a difference of almost 50 million years between the pollen found and a different plant, so it is confirmed that in the Cretaceous there were already angiosperms but that their origin is much earlier.
In the Jurassic, however, coniferous forests are still important and ferns and other seedless plants are losing importance.
The Jurassic Period is the height of the giants, the largest land animals are from this period. It is true that during the Cretaceous there were also large specimens, but the largest are Jurassic.
During this period, the boom of the Sauropods, the largest land animals that have ever traveled the Earth, is particularly noteworthy. These large dinosaurs, such as the Brachiosaurus or the Diplodocus, were characterized by long necks and titanic proportions, and some of them had long tails that they used as a whip.
In the group of carnivores, there are also large specimens, although nothing compared to the sauropod titans, and specimens such as the Allosaurus or Ceratosaurus stand out. Although one of the most striking evolutionary facts did not appear in the large specimens, but in the small ones: the development of the pen.
From this period dates the well-known fossil of Archaeopteryx, which can be considered the first prehistoric bird, although even with reptilian features such as the snout with teeth, claws and a long tail, in addition to a hip Saurischia, which indicates that is an ancestor of the current birds but belongs to another group (the current birds belong to the Clado Manirraptora).
Not only were there giants on land, there were also giants at sea.
At this time practically all the fauna was very diversified, and in the sea, there were great radiations like the plesiosaurs and the ichthyosaurs. These animals were reptiles of the Lepidosauromorpha group, of which we have already spoken in the Triassic.
Today there is no such aquatic reptile, all of which were extinct in the Cretaceous, but their fossil remains are relatively abundant and well preserved and teach us that the hydrodynamic designs of today’s fish and cetaceans were already used in species that existed almost 200 million years ago.
Here we show you the dinosaurs that lived in the Jurassic period: