What were the first dinosaurs in Earth's Triassic period?"
The Triassic is a geological era that is located between the Permian and Jurassic,
lasting approximately 250 to 200 million years ago. During this period, the Earth experienced a
series of important climate and geological changes that greatly influenced animal and plant life.
What would you say if we took a walk? As we journey through the Triassic,
we will discover how life on Earth has evolved and changed over millions of years,
and how the events of the past have shaped the world we know today.
The Triassic was an incredibly exciting time for our planet. Our planet was slowly
recovering from the massive extinction that had hit the continents at the end of the Permian,
and new forms of life were beginning to emerge. The sky was crossed by spectacular flying
creatures, such as Pterosaurs, while in the seas monstrous creatures like Mosasaurs were stirring.
But the true protagonist of the scene was the vegetation, with ferns and ginkgo forests
extending for kilometers, and giant trees like the Archaeopteris rising like towers towards the sky.
The continents were still reunited in the single supercontinent of Pangea,
and the emerging lands were dominated by large predators such as Therapsids and Dinosaurs.
Life was wild and uncontrollable, and every day was a struggle for survival.
The period began with a series of large extinctions, in which about 75% of marine
species and 80% of land species disappeared. This allowed new forms of life to evolve and
colonize the emptied ecosystems. The first extinction saw the disappearance of about
20-25% of species including many marine forms such as trilobites and brachiopods.
The second extinction, which struck at the end of the Upper Triassic, saw the disappearance of about
75% of marine and land species, including many marine reptiles such as plesiosaurs.
The causes are still the subject of debate, but some theories suggest
that the blame could have been due to extreme climate events,
active volcanoes, meteorites, or changes in the composition of the atmosphere.
During the Triassic, the Earth was crossed by major climate changes,
which led to an increase in global temperature and a reduction in humidity. This led to the
formation of large deserts, which influenced the distribution of plant and animal species.
The average temperatures were generally higher than today. Studies of sediments and fossilized
remains indicate that they were between 20 and 25 degrees Celsius in the equatorial zones and
between 15 and 20 degrees in the temperate zones. In addition, the Triassic was a period of great
tectonic movements, during which new continents were formed and existing ones were split.
This influenced the distribution of animal and plant species,
creating new opportunities for evolution. New species of plants appeared, including
the first trees and the first seed plants. The first true reptiles also appeared, including
the ancestors of today's crocodiles, turtles, and lizards. And the first mammals also appeared!
The flora of the Triassic was also characterized by great diversity.
Among the most common plant species were huge ferns, small underbrush palms, the omnipresent
ginkgo, and vast stretches of conifers. The fauna of the Triassic was characterized
by the presence of reptiles, which represented the majority of animals of the period.
Among the most common reptiles were dicynodonts, therapsids, and temnospondyls.
These animals were adapted to the warm and dry climatic conditions of the era
and formed large herds that roamed the forests feeding on amphibians and especially insects,
in competition with the first mammals,
which were small and poorly diversified, also constantly searching for small prey.
Several species of fish, crustaceans, and mollusks lived in the seas and freshwater. In general,
the fauna was characterized by a great diversity of species, which had adapted
to the environmental conditions of the era. Among these, are the first species of dinosaurs!
It seems that the first dinosaurs appeared during the lower Triassic,
around 230 million years ago. They were small creatures, very similar to reptiles,
but then they diversified into a wide range of shapes and sizes.
Dinosaurs in fact dominated the Earth for over 150 million years until their massive
extinction which occurred around 66 million years ago, at the end of the Cretaceous period.
The first dinosaurs descended from reptiles, obviously... but from reptiles,
they differed in some pelvic characteristics able to allow them bipedal locomotion. In addition,
dinosaurs had a series of muscular, skeletal, and cardiovascular features that made them more
active and able to sustain more intense efforts than those reptiles could afford.
These changes allowed them to become the first animals to have an upright posture and to develop
a series of specific adaptations for hunting, escape, or defense. Of these first representatives
of those that in our collective imagination would become the monsters of the Cretaceous, we believe
that the most interesting and typical of the period are those that we describe here below…
The Coelophysis, also famous for the long sequences dedicated to him in a couple of
films of the Jurassic Park saga, was one of the first biped dinosaurs that lived around
210-200 million years ago. It was about 3 meters long and weighed about 40 kg. It was a light
carnivore with long and slender legs and a long and muscular tail. It was very agile and fast,
perfectly adapted to capturing small prey such as reptiles and amphibians. The animal had a
long and narrow head (about 270 millimeters), with large eyes facing forward that gave it
a stereoscopic vision and, as a result, an excellent perception of depth. It is
believed that the Coelophysis hunted in packs, using its speed and agility to catch prey.
The Plateosaurus was one of the first herbivorous dinosaurs,
also living during the same period. It was about 10 meters long and weighed around 4 tons.
Plateosaurus had the typical shape of a bipedal herbivorous dinosaur: a small skull,
a long and flexible neck composed of 10 cervical vertebrae, a stocky body,
and a long mobile tail composed of at least 40 vertebrae. Its arms were rather short,
but very muscular and strong, with hands adapted to grasp objects in a powerful
grip. The hind limbs were placed under the body, with slightly bent knees and ankles,
while the foot was digitigrade, meaning the animal walked and ran on its toes.
The Plateosaurus' tail was typical of dinosaurs, very muscular and with high mobility. The animal
was primarily or exclusively fed on plants. The eyes were directed to the sides, not frontally,
providing a 360-degree view, useful for identifying potential predators.
Then there was the Herrerasaurus, which lived about 230-220 million
years ago. Measuring from three to four meters long and weighing up to 300 kg,
this carnivorous dinosaur was certainly of considerable size, but certainly,
not one of the top predators of its time, as in the same places it frequented lived giant
primitive archosaurs, such as the Saurosuchus. The reason for the success of an animal like
Herrerasaurus was most likely due to a characteristic of the first dinosaurs,
namely bipedality. Herrerasaurus, in fact, was one of the first carnivorous dinosaurs,
the theropods, which subsequently invaded every part of the globe, including Antarctica.
The body of this dinosaur was slender and robust; the neck was moderately elongated
and the hind legs were long and powerful. The front limbs, with five-fingered hands provided
with powerful claws, were used to grasp the prey, which was then further injured by the
long teeth present in the wide mouth. Probably the main prey of Herrerasaurus
was the large and slow Rincosaur, a strange reptile with a beak related to archosaurs.
At its best, this creature was at the top of the food chain, and when it went extinct,
it left a niche that was then occupied by the large carnivorous dinosaurs of the Jurassic.
As we have already said, although aggressive and well-equipped with teeth, Herrerasaurus
was not the fiercest and largest predator of those times... In the late Triassic swamps,
in fact, prowled the Saurosuchus Galilei; a giant crocodile up to 9 meters long,
with long legs and a body, raised off the ground. The weight of this predator, the largest in its
ecosystem, should have been around two or three tons. The long muscular tail
was probably held raised off the ground, used to balance the body and as a weapon.
It is important to remember that all of these creatures, although they can be
considered the first dinosaurs to ever appear on Earth, were still cold-blooded reptiles.
This means that their body temperature depended on the external environment.
Only in the Cretaceous, a hundred million years later, did dinosaurs develop homeothermy,
or the ability to maintain their body temperature independently of the external temperature.
Another question that one might ask comparing the characteristics of the
first dinosaurs to those of the "monsters" of the Jurassic and Cretaceous periods, could be:
"Why did this race to gigantism occur?" Unfortunately, the precise cause is not
yet fully understood by paleontologists. However, several theories try to explain
this phenomenon. One of the most widely accepted is based on climate change.
During the Triassic, the climate was warm and humid, with lush vegetation and little seasonal
variability. During the Jurassic and Cretaceous periods, the climate became drier and warmer,
which could have favored the growth of plants with high cellulose content,
richer in nutrients than Triassic plants. This would have allowed herbivorous dinosaurs
to grow and become ever larger, thanks to access to a greater amount of food. And obviously, as in
a kind of arms race, even carnivorous dinosaurs were forced to evolve into suitable bodies.
The Triassic was thus a transitional era--a biological laboratory where for
50 million years evolution shuffled its cards, preparing in great detail for the
entry of the most spectacular assemblage of animals ever seen on our planet!