248-208 Million Years Ago

 

As the Mesozoic era begins, we see the rise of the what is known as the dinosaurs.  Pterosaurs (flying reptiles) also made their first appearance here as well as frogs, turtles, and crocodiles. During the Late Triassic period, many small mammals also appeared.

During the Triassic, almost all the Earth's land mass was concentrated into a single supercontinent centered more or less on the equator, called Pangea (meaning - all the land). This took the form of a giant "Pac-Man" with an East-facing "mouth" constituting the Tethys sea, a vast gulf that opened farther westwards in the mid-Triassic, at the expense of the shrinking Paleo-Tethys Ocean, an ocean that existed during the Paleozoic. The remainder was the world-ocean known as Panthalassa (meaning - all the sea). All the deep-ocean sediments laid down during the Triassic have disappeared through subduction of oceanic plates; thus, very little is known of the Triassic open ocean.

The supercontinent Pangaea was rifting during the Triassic, especially late in the period, but had not yet separated; the first marine sediments in the earliest rift, which separated New Jersey from Morocco, are Late Triassic in origin. Because of the limited shoreline of one super-continental mass, Triassic marine deposits are globally relatively rare, despite their prominence in Western Europe, where the Triassic was first studied. In North America, for example, marine deposits are limited to a few exposures in the West. Thus Triassic stratigraphy is mostly based on organisms living in lagoons and hypersaline environments, such as Estheria crustaceans.

The Triassic climate was generally hot and dry, forming typical red bed sandstones and evaporites. There is no evidence of glaciation at or near either pole; in fact, the polar regions were apparently moist and temperate, a climate suitable for reptile-like creatures. Pangea's large size limited the moderating effect of the global ocean; its continental climate was highly seasonal, with very hot summers and cold winters.

The first dinosaurs appeared : The Earth looked much different at the beginning of the Triassic period than it does today, as all of the land was massed in one super continent called Pangaea. The climate was hot and dry. Mammal-Like Reptiles dominated the land and some of them grew to lengths of almost 20 feet. The first dinosaurs also appeared during this time and these included the dog-sized meat-eaters Eoraptor ("the dawn reptile") and Hererrasaurus. In the late Triassic period prosauropods, 20-foot-long plant-eaters, also emerged. They had small heads and were able to walk on two or four legs.

A massive extinction paved the way for dinosaurs: The greatest known extinction event in Earth's history occurred at the beginning of the Triassic. This event paved the way for dinosaurs to supplant Mammal-like Reptiles as the most dominant creatures on the planet. While not all of the Mammal-like Reptiles vanished, they became vulnerable to the emerging dinosaurs. Many scientists believe that as the dinosaurs got bigger, faster and more ferocious, they killed most of the Mammal-Like Reptiles, and those that survived were the smallest of these creatures. Eventually, the only ones left were the very smallest and these evolved into early mouse-sized mammals.

Dinosaurs begin to grow and diversify : The plant-eating dinosaurs, which appeared during the mid-to-late Triassic more than 200 million years ago, were the first ornithischians, or bird-hipped dinosaurs, and were no bigger than turkeys. Huge ferns and other primitive non-flowering trees dominated the land. Grass never grew during the Triassic and the dinosaurs got bigger and bigger as a result of having little competition from any other forms of life on the land. One of the most significant developments to occur during the latter part of the Triassic was that some creatures took to the air. Two families of animals began to develop at this time - flying reptiles, or Pterosaurs, and the first members of the family that became birds.

These are some of the dinosaurs that existed throughout the Upper Triassic Period.

Eoraptor | Melanorosaurus | Mussaurus | Plateosaurus

 

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