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Mesozoic Era

Mesozoic Era: Facts, Timelines & Animals

Often dubbed “The Age of the Dinosaurs”, it was during this era that Earth experienced the rise and fall of some of the planets most notable animals. From the mighty Tyrannosaurus Rex (T-Rex), to a diverse ecosystem of mammals and birds.
From the Greek for “middle life”, this Era spanned a period from 250 up to just 65 million years ago. The Mesozoic Era is generally divided into three separate ‘Periods’ (Triassic, Jurassic and Cretaceous).

The Mesozoic Timeline

The Mesozoic Timeline

Entering and leaving the scene with a bang, the Mesozoic Era both started and ended with a mass-extinction event, resulting in the transition from the Paleozoic Era to the Mesozoic Era. The initial extinction event, resulted in around 70% of all land life and 95% of all marine life ceasing to exist, setting the stage for the dinosaur’s dominance as the apex creatures of Earth.
Leaving as dramatically as it came, the Era ended with what we know as “The Great Extinction”, and the end of dinosaurs’ reign.

Mesozoic Climate
The climate during the Mesozoic Era was notably warmer than that we experience on earth today, with less dramatic differences in temperatures between the South and North poles. The formation of a singular supercontinent meant that the interior was less influenced by any temperature modulating controls the oceanic waters may have had.

Pangea was covered in desert and arid environments, with a belt of tropical rainforests in the regions surrounding the equator.
During the Triassic period, the climate was arid and dry, but this began to shift as the era neared the Jurassic period, during which oceans rose and exposed land flooded. This resulted in an increasingly humid climate that lasted well into the Cretaceous period.

Continents at the beginning of the Mesozoic Era Continents at the end of the Mesozoic Era Mesozoic Tectonics
At the start of the Mesozoic Era, we had one major supercontinent, formed when other continents merged to create Pangaea. It was also during this time when Pangea separated to become two distinctive continents: Gondwana and Laurasia.
Laurasia would go on to split into what would become Eurasia and North America, whereas Gondwana would become what we know today as Australia, Africa, South America and Antarctica, as well as the subcontinent, India.
A later collision of India with Eurasia would result in the formation of the Himalayas.

Mesozoic Life
The Mesozoic Era experienced a dramatic shift in life from that of the Paleozoic Era. With a mass extinction event wiping out the majority of land and marine life leading into the Era, the earth was but a canvas ripe for new evolutionary breakthroughs.
Early Mesozoic life was slim, with the remaining biota starting the long and tumultuous task of recovering and diversifying, beginning the start of ecosystems resembling those of modern-day earth.
Vertebrates, having faired better than their invertebrate counterparts in the last extinction event, saw marked diversification throughout the Triassic period.

Triassic Period

During the Triassic period, terrestrial environments were dominated by a group of ‘mammal-esq’ reptiles known as therapsids, and the early ancestors of dinosaurs, the thecondonts.
Mammals and Reptiles
It wasn’t until the late Triassic period that the first mammals arrived on the scene. These shrew-like omnivores were quickly followed by a range of reptiles, lizards, turtles and the famed pterosaurs.

Marine Life

Meanwhile, oceans were dominated by mollusks, including gastropods, bivalves, and ammonites. Later on, we see the emergences of fish, marine reptiles, and sharks, the likes of which became the apex predators of the ocean waters.

Plants and Insects
There wasn’t a lot happening on this front. The dry climate left much of the interior desert, with only gymnosperms surviving, resulting in the reforestation of conifers. Ferns and mosses maintained a foothold in coastal areas.
Meanwhile, scorpions, spiders millipedes and beetles continued to thrive, with the only newly emerged insect being the grasshopper.

Jurassic Period

This was a time of dynamic global changes including continental shifts, emerging oceanic patterns and new biological systems.
Mesozoic Era First Flowering PlantsThe Rise of the Dinosaur
On land, the dinosaur reigned supreme, though we also saw the emergence of birds and early mammals.
Oceanic Life
Oceans were incredibly diverse during this period, with reef ecosystems giving life to a broad range of shallow-water invertebrates, the likes of which supported large swimming predatory reptiles.

Cretaceous Period

Plant Life

Here we see an exciting development: the introduction of flowering plants, with the oldest angiosperm fossil found to dating back to at least 122 million years ago. Pollination and cross-pollination of these plants was further supported and fostered by the already established insect population at the time.

Animal Life

Here we see birds take their place in the skies alongside the mighty pterosaurs. During this period birds experienced significant diversification and evolution.
Large herds of herbivores were thought to have thrived at this time, as did large terrestrial apex predators.

Mesozoic Extinction Event Mesozoic Extinction Events

This era started and ended with two of the largest mass extinction events the planet has experienced. An estimated 252 million years ago, the end-Permian extinction resulted in wiping off the face of the earth the majority of life. This set the stage for rapid evolutions and the establishment of large reptiles, a diverse oceanic ecosystem, and of course, domination by dinosaurs on land.

As abruptly as it began, this era came to an end some 66 million years ago in yet another extinction event, the likes of which wiped out an estimated 70% of all plant and animal life on earth.
Although the exact cause is up for scientific debate, plausible theories including meteorite impact, progressive climate change and supervolcanic activity. Likley it was a combination of events That put an end to this era.

There are two known events that took place about this time that were big enough to be likley causes. The now famous Chicxulub impact crater off the coast of Mexico has been dated to about 66 million years ago. It is the smoking gun of an extremely large asteroid impact that caused tsunamis, fire storms, and rapid climate change. This stands out as a primary trigger for mass extinction. But hold on there is more evidence. There is a place in India called the Deccan Traps. It is the remains of a massive volcanic event called flood basalts. Today the Deccan Traps cover an area of about 200,000 square miles over a mile deep. It has been estimated to have been three times that size originally. There is some variation when it comes to dating this event which lasted .8 to 2 million years. Many researchers believe it began about 65 million years ago and probably overlaped the Chicxulub asteroid event. 

There are other theories about this extinction, but these two events were a likley one two punch that took the dinosaurs, marine reptiles, and about 75% of all living things.
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