What was the Earth like during the Jurassic period?
Approximately 65 million years ago, the Earth
was inhabited by reptiles of all sizes and colors; these managed to thrive for millions
of years to dominate every corner of the planet, from the Earth to the sky and the oceans.
But one fateful day, a massive rock from space ended this paradise, causing a cataclysm that
killed 70% of living beings, ending the reign of those who, until then, ruled the world.
But what was the planet like during the time of the dinosaurs before the meteorite fell?
Did the same plants exist as today?
Were there winters?
Today we will find out!
Mesozoic The planet's history is divided into eras,
periods, and other classifications created by paleontologists to mark the beginning and
end of important dates in the fossil record.
Usually, when discussing the Jurassic period, most people imagine dinosaurs, but this is
a mistake.
Do not forget that dinosaurs are a group of animals that comprises a wide variety of species,
and these species lived for several periods, including the Jurassic.
Today the only dinosaurs left are birds.
Birds are not descended from dinosaurs; birds are dinosaurs.
But if we talk about the first dinosaurs that emerged in the world, these emerged in the
Triassic period and lived during the Jurassic and Cretaceous; these three periods are what
we know as the Mesozoic era.
The beginning of the great reptiles (Triassic) During the Triassic, almost all lands were
concentrated in a single continent centered roughly on the equator called Pangaea.
This continent was shaped like a "C," and to the east, in the hollow of the "C," was
the Tethys Ocean, and surrounding it all was the Panthalassa Ocean (the "universal ocean").
All deep ocean sediments deposited during the Triassic have disappeared through the
subduction of oceanic plates, so very little is known about the open ocean during the Triassic.
The Triassic climate was generally hot and dry and resulted in the formation of extensive
deserts and evaporites.
Pangaea's large size limited the ocean's moderating effect; Its continental climate was highly
seasonal, with sweltering summers and frigid winters.
It probably had intense monsoons at the equator.
There is no evidence that this period had glaciation near or at either pole.
The polar regions were seemingly wet and temperate, with extensive forests and huge rivers, a
climate suitable for reptile-like creatures.
Among the arboreal vegetation, there were some conifers and ginkgos.
Ferns predominated in humid areas, along with cycads with a morphology similar to palm trees
and some predecessors of today's pines.
Forests of gigantic ferns and bulky conifers populated Gondwana.
There is evidence that beetles were involved in pollinating some gymnosperms, but otherwise,
there were few of these plants trying to attract insects; it even seems as if cycad cones were
designed to scare them away.
More than half of the known species of insects were equipped to pierce, nibble and suck plant
bodies.
Reptiles dominated the earth's surface in this period.
However, most genera of Permian mammalian reptiles suddenly disappeared.
In the early Triassic, a few genera of predators remained, and the large herbivore Lystrosaurus,
famous for its fossil presence in many of the widely dispersed fragments of Gondwana.
Mammalian reptiles diversified during the Triassic, playing an important ecological
role.
Among the herbivorous species were dicynodonts, similar to modern hippos; rhynchosaurs, similar
to modern pigs; and cynodonts, similar to today's weasels.
All of them disappeared from the face of the earth strangely and suddenly: It was the first
great mass extinction of terrestrial fauna on our planet.
The thecodonts that relieved them disappeared in the second great extinction, which occurred
at the end of the Triassic.
Only turtles, crocodiles, dinosaurs, and some small mammals survived.
Most of the dinosaurs such as theropods and prosauropods, appeared at the end of the Triassic,
they quickly colonized the land without competition and with empty ecological niches.
Highlighting the Procompsognathus and Plateosaurus.
Several small reptiles developed membranes over the limbs, allowing them to glide.
Some genera had these wings on the front legs and others on the hind legs.
The most abundant were the pterosaurs that were quickly able to make flights of long
duration, covering great distances that allowed them to extend their population.
The Golden Age of Dinosaurs (Jurassic) After the emergence of the first dinosaurs,
they would soon spread and populate the entire planet, filling every hole and every corner
of the world with an immense variety of animals that adapted to all ecosystems.
This period is characterized by the hegemony of the great dinosaurs and by dividing Pangaea
into two continents, Laurasia and Gondwana.
From the latter, Australia was divided, just as Laurasia was divided into North America
and Eurasia.
The landscapes of the Jurassic were richer in vegetation than those of the Triassic,
especially at high latitudes.
The heat and humid climate allowed jungles and forests to be part of many Jurassic landscapes.
The forests extend throughout the Earth's surface and include families such as pine-like
conifers and araucarias, accompanied by different types of ferns and palm trees.
During this period, the first frogs appear.
Crocodiles were already fully established, and the vast Archosaurs remained dominators
of the terrestrial ecosystem.
In this period, the Sauropods significantly increased in size; examples of this are the
Diplodocus and Brachiosaurus, which reached sizes of up to 35 meters, being the largest
land animals that have populated the Earth.
Predators also grew up adapting to new hunting methodologies.
Some, such as Allosaurus, dominated the Jurassic lands.
In addition, other enormous phytophagous dinosaurs, such as Stegosaurus, emerged with bony plates
on the back and spiny defenses on the tail.
During this period, the first small birds appear.
But those who dominated the skies in these times were the great Pterosaurs that came
to have a wingspan of up to 15 meters, the more enormous flying creatures that have existed
in the entire history of the planet.
This family of reptiles, which were not dinosaurs, fed on fish in the great seas with their long
beaks possessing pointed teeth.
The most evolved forms of marine life during the Jurassic were fish and reptiles.
At the same time, the oldest is the ichthyosaurs, which survive the change of period.
These animals shared the seas with the first aquatic crocodiles, which had fins instead
of legs, and with teleosts, predecessors of most fish today.
However, the waters of the Jurassic were ruled by the Plesiosaur, a vast aquatic reptile
with a long neck and fins that gave it a lot of agility to hunt its prey.
The beginning of the end (Cretaceous) The dinosaurs' reign extended for almost 200
million years, and during all that time, they evolved and adapted to give rise to species
that still live with us today.
During the Cretaceous, the sea level was continuously rising.
This growth took the sea level to heights never reached before; even previously, desert
areas became floodplains.
At its peak, only 18% of the Earth's surface was above water level; as a reference today,
the surface emerged is 29%; this means that during this period, animals and plants had
much less space to develop and live, which eventually made them compete for food.
Temperatures rose to their peak about 100 million years ago, when there was virtually
no ice at the poles.
Sediments show that temperatures at the surface of the tropical ocean must have been 9 to
12 °C warmer than today, while deep ocean temperatures must have been even 15 to 20
°C higher.
During the Cretaceous, several classes of reptiles reached their peak, especially dinosaurs,
which inhabited all regions of the planet then, diversifying into a wide variety of
animals capable of surviving in all ecosystems.
At the end of the Cretaceous, oceanic plankton evolved to take on an appearance much like
modern plankton.
The ichthyosaurs had practically disappeared at the end of the Early Cretaceous.
Their place was taken by new large sharks and large teleosts such as Xiphactinus, which
measured between 2 and 4 meters in length.
These, in turn, coexisted with giant sea turtles such as Archelon, more than 3 meters long
and with fins that extended both, exceeding the animal's length.
Stripes were also standard in the seas.
Among reptiles, elasmosaurids, a group of long-necked plesiosaurs, reached lengths of
up to 12 meters.
Mosasaurs, which reached lengths of 17 meters, were considered the fiercest marine predators
in the Late Cretaceous as they were giant lizards (the largest that have ever existed)
related to modern snakes.
Mosasaurs possessed long jaws with sharp teeth attached to a slender, extensive body with
paddle-shaped limbs.
They had to feed on fish, although fossils of ammonites have been found with dental row
markings that fit precisely with that of mosasaurs, so it is most likely that they also hunted
larger animals.
On the other hand, the aerial animals were still the Pterosaurs that, in this period,
acquired a great variety of sizes.
At the same time, several groups of dinosaurs began to develop feathers on their bodies
to protect themselves from the weather.
Mammals were still a small and relatively minor component of fauna.
During this time, the dinosaurs reached significant adaptive radiation.
That is why there were a large number of species with very different lifestyles and morphologies.
The wide spread of ornithopods throughout the Cretaceous, as well as their diversity
among the different native faunas, are indications of their success.
In the Early Cretaceous, we find Iguanodon and Hypsilophodon.
Iguanodon was the most common of the large ornithopods.
It was a biped 10 meters long, with a skull similar to that of a horse, with long jaws
and eyes in a very posterior position.
Hypsilophodon is the second most abundant dinosaur.
It was a small animal (3 to 5 meters in length) with legs designed to run fast and a rigid
tail, which balanced it during the race.
The hadrosaurs were significant, 10 to 15 meters in length, and all possessed bodies
that conformed to the model of iguanodonts.
The anterior part of the muzzle is flattened, with the typical duckbill shape, and the teeth
are arranged in multiple rows.
Ceratopsids lived in North America and Asia and had a large, beaked head, which, seen
from above, had a triangular shape, a variable number of horns, and a bony shield that protected
the shoulder region and constituted the plane of insertion of the powerful mandibular musculature.
The largest ceratopsids reached 9 meters in length, with horns of almost 1 meter and weights
of up to 6 tons, like the Triceratops.
On the other hand, pachycephalosaurs were another group of bipedal ornithopods with
thick skulls.
In the late Cretaceous, ankylosaurs, which had appeared in the Jurassic, diversified.
They were closely related to stegosaurs and were frequently large animals, up to 10 meters
in length and 6 tons in weight.
They specialized in armor, with plates under the skin of the back, neck, and tail, as well
as bone reinforcements in the skull and even above the eyes.
Among the carnivorous theropods, we could include various forms.
The development of curved claws, specially designed to gut prey, seems to have occurred
independently in several theropods, such as the famous Tyrannosaurus rex) and Tarbosaurus,
very similar to the previous one, was probably the top predator in the world.
Tyrannosaurus was the largest terrestrial carnivore of its time, only slightly surpassed
by Giganotosaurus and Spinosaurus.
Tyrannosaurus reached a length of thirteen meters, a height of 4.8 meters, and a weight
of 5 tons.
In their jaws were aligned teeth 15 centimeters in length.
Tyrannosaurus' hind legs were solid and massive, with three toes on each foot.
On the other hand, his arms seem almost ridiculous: extremely thin and so short that they did
not reach the mouth and with only two fingers.
Throughout the Cretaceous period that lasted more than 100 million years, a variety of
dinosaurs populated the entire world until a cataclysm from space ended their reign in
the blink of an eye.
The last times of the Mesozoic era are known as the Cretaceous.
During this period appear, many of the dominant lineages of animals and plants have survived
to this day.
Most Cretaceous tetrapod vertebrates were reptiles, which dominated aquatic (plesiosaurs,
ichthyosaurs, and mosasaurs), terrestrial (non-avian dinosaurs), and aerial (pterosaurs
and avian dinosaurs) environments.
Avian dinosaurs, commonly called birds, are included within the lineage of carnivorous
dinosaurs (theropods) and possess certain characteristic features, such as the presence
of feathers and wings, which were already present in ancestral genera such as the famous
Velociraptor.
All of the aforementioned aquatic reptiles, and most dinosaurs, except birds, disappeared
in a great event that radically changed the course of life history.
This complex and momentous phenomenon is known as the Cretaceous extinction, which occurred
about 66 million years ago.
The most accepted theory is that this great extinction was caused by a giant meteorite
that fell in the Yucatan Peninsula.
If you would like to know more about the dinosaurs' last day, let us know with your comment.