You must have seen the movie Jurassic Park series, a pragmatic paleontologist visiting an almost complete theme park is tasked with protecting a couple of kids after a power failure causes the park’s
cloned dinosaurs to run loose. But actually, you know what, most of the dinosaurs in the movie don’t belong to Jurassic. “T-rex, Pachycephalosaurus, Velociraptor, Triceratops, Parasaurolophus, Ichthyosaurs, Ankylosaurus, these dinosaurs are all from the Cretaceous period.”
Confused? To figure this out clearly, we need to know when did dinosaurs appear first.
Dinosaurs first appeared in the Mid-Triassic, and became the dominant terrestrial vertebrates in the Late Triassic or Early Jurassic, occupying this position for about 150 or 135 million years until their demise at the end of the Cretaceous. It can be seen that the Mesozoic is subdivided into three major periods: the Triassic, Jurassic, and Cretaceous, which are further subdivided into a number of epochs and stages.
The Triassic ranges roughly from 252 million to 201 million years ago, preceding the Jurassic Period. The period is bracketed between the Permian–Triassic extinction event and the Triassic–Jurassic extinction event.
The Jurassic ranges from 200 million years to 145 million years ago and features three major epochs: The Early Jurassic, the Middle Jurassic, and the Late Jurassic.
The Cretaceous is the longest period of the Mesozoic but has only two epochs: Early and Late Cretaceous.
Representative dinosaurs in each period:
Triassic – Eoraptor:
The first dinosaur we’ll focus on is Eoraptor, and this dinosaur was likely an omnivore and it lived about 230 million years ago. This dinosaur was only 3 feet long and 25 pounds.
Its name means ‘dawn plunderer or destroyer’ because it is an early dinosaur (the dawn of the dinosaurs) and ‘plunderer/destroyer’ because some scientists believe its claws tore apart (or destroyed) its prey.
There is some debate about the classification of Eoraptor. Some scientists suggest it was an early theropod, which is a group of primarily meat-eating, bipedal dinosaurs that would later include fierce predators like T. rex. Whereas others suggest it belonged to a group of Sauropodomorpha, which were long-necked, herbivore dinosaurs.
Jurassic – Brachiosaurus
Brachiosaurus is one of the best-known sauropods, belonging to the family Brachiosaurid. It is one of the biggest land animals yet found. Its name, meaning “arm lizard”, is derived from the prodigious length of its front legs. The first thought of as swimmers, the Brachiosaurus is now thought of as land roaming. Brachiosaurus probably had no predators, because of its enormous size; its defense was its size. Brachiosaurus was a herbivore, a treetop eater, that ate the most elevated plant material (like conifers leaves, and fruit).
Cretaceous – T-rex
T-rex is one of the most well-represented of the large theropods. It lived throughout what is now Western North America, on what was then an island continent known as Laramidia. The Tyrannosaurus rex is revered as one of the most fearsome creatures to inhabit the earth, with an average weight of six tons and the power to tear off 500 pounds using its massive jaw.
U-Toward the close of the Cretaceous, vast herds of horned beasts such as Triceratops munched cycads and other low-lying plants on the northern continents. The carnivore Tyrannosaurus rex dominated the late Cretaceous in the north while monstrous meat-eaters like Spinosaurus, which had a huge sail-like fin on its back, thrived in the south.
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