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The Jurassic Period corresponded to the middle part of the Mesozoic Era. It happened between 201.3 million and 145 million years ago, after the Triassic period and before the Cretaceous period.
Pangaea, the supercontinent of the Triassic and Jurassic periods, fragmented during that time. Central Atlantic and Gulf of Mexico basins opened as Laurentia, up north, began to break apart into landmasses that would become North America and Eurasia.
The southern half, Gondwana, was migrating apart into what would become Antarctica, Madagascar, India, Australia, Africa, and South America.
Due to this rifting and the typically warmer global temperatures, the group of reptiles known as dinosaurs was able to diversify and become dominant.
Even the recently established shallow interior seas were teeming with life. Sharks, rays, enormous marine crocodiles, and plesiosaurs with long necks and paddle fins topped the food chain.
The seas teemed with fish-like ichthyosaurs, squid-like cephalopods, and ammonites with coil-shaped shells. The warm seas supported the growth of coral reefs, providing a favorable environment for sponges, snails, and mollusks. The overpopulation of microscopic, free-floating plankton may have caused the reddish hue of some oceanic regions.
Jurassic Plant Life
By the Mesozoic, organisms had developed the ability to survive on land and in water. Low-growing Bryophytes like mosses and liverworts that lacked vascular tissue and could only thrive in wet, shady places were the ancestors of all land plants by the start of the Jurassic.
The most common early Jurassic plants were ferns and gingkoes, which used a spore reproduction method and had roots and vascular tissue to transport water and nutrients.
The Jurassic period saw the development of a novel strategy for plant reproduction. Gymnosperms, which include conifers, are distinguished by their ability to disperse pollen by the wind thanks to their distinctive cones. As a result of the increased opportunities for genetic mixing afforded by bisexual reproduction, gymnosperms had established a global presence by the end of the Jurassic.
In addition, fossils show that the first blooming plants, or angiosperms, appeared during this period in the middle to late Jurassic. Angiosperms were previously thought to have originated during the Cretaceous epoch by paleobotanists. In contrast to gymnosperms, flowering plants would have been uncommon in Jurassic times.
The Jurassic Dinosaurs
The Triassic Period ended with a cataclysmic extinction. 50% of all species were extinct then, including the dinosaurs' biggest rivals, the crocodile-like pseudosuchians.
Dinosaurs quickly became the dominant land animals of the time. Meet Jurassic Dinosaurs.
Allosaurus was one of the several Jurassic dinosaurs unearthed in the western United States' Morrison Formation (a Jurassic Period rock stratum). Allosaurus was a bipedal, massive theropod dinosaur. It would have been a top predator, feasting on sauropods and Stegosauria like Stegosaurus.
Apatosaurus is a huge sauropod dinosaur that inhabited North America during the Late Jurassic.
Archaeopteryx exhibits dinosaur traits such as teeth, clawed wings, and a tail, as well as bird traits such as a wishbone and flight feathers. Scientists are uncertain whether archaeopteryx was capable of real flapping flight or was merely an advanced glider.
Brontosaurus translates to "thunder lizard" Scientists believe that the brontosaurus (and other sauropods) may have cracked its enormous tail like a whip to deter potential predators.
Camarasaurus is North America's most abundant Jurassic sauropod. Its name means 'chambered lizard' because its hollowed-out bones contain air-sacs that helped dinosaurs breathe and lightened their skeletons.
Late Jurassic Camptosaurus existed in North America. Ornithopod dinosaurs possessed advanced plant-chewing systems.
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The carnivorous Ceratosaurus dinosaur was characterized by a horn protruding from its nose and pronounced ridges above its eyes.
The meat-eating Compsognathus was about the size of a turkey. The bodies of the lizards that this swift predator ate have been recovered in their fossilized remains. For a long time, Compsognathus was the smallest dinosaur that people knew about.
There was a theropod dinosaur called Dilophosaurus that lived in the Jurassic period. The skull of this unique dinosaur was crowned with two thin crests of bone. The scientific name for the dinosaur literally translates to "lizard with two crests."
Diplodocus was a common big dinosaur. The rear legs of Diplodocus were longer than the front legs, and its hips to shoulders slanted downwards.
It is believed that Diplodocus could stand on its hind legs using its enormous tail as a prop. This would have allowed the large lizard to reach vegetation that would have been inaccessible otherwise.
Megalosaurus was the first named dinosaur. It was one of the three species selected by the English naturalist Richard Owen to introduce the world to a "new" form of an animal, the dinosaurs.
Megalosaurus moved on its hind legs while balancing itself with its tail. It was a predator, and sauropods and stegosaurians were likely among its prey.
Stegosaurus is among the most recognizable Jurassic dinosaurs. It was a robust plant-eating creature. Its shorter forelegs than its rear legs gave its body a downward tilt.
The Stegosaurus is distinguished by the two rows of huge plates that run along its back. These may have been used to defend against predators or regulate the animal's body temperature.
Vulcanodon was a sauropod that lived in southern Africa during the Early Jurassic. The name of this creature translates to "Vulcan tooth." This alludes to the volcanic rock in which the specimen was discovered and the nine sharp teeth discovered with it.
The Jurassic's Early Mammals
Although dinosaurs were the dominant land animals, they were not alone. Most early mammals were little herbivores or insectivores that did not compete with larger reptiles. Adelobasileus, a shrew-like creature that lived during the late Triassic, has a mammal's ear and jaw bones.
Chinese scientists announced the discovery of Juramaia in August 2011. This mid-Jurassic mammal is a clear eutherian, an ancestor of placental mammals, demonstrating that placental mammals originated considerably earlier than previously believed.
Marine Life in the Jurassic
The plesiosaurs and the ichthyosaurs were the two most prevalent types of marine reptiles throughout the Jurassic epoch. At the start of the Jurassic Period, the ichthyosaurs dominated the marine environment as the top predators. By the end of the Period, however, the plesiosaurs had become the dominant marine vertebrates.
One of the most well-known examples of this group is Ichthyosaurus. With large eyes, four flippers, a dorsal fin, and enormous jaws full of fangs, this dolphin-like predator measured 3 meters in length.
When it came to plesiosaurs, there were two primary varieties. Each used all four of its flippers to propel itself through the water.
The Plesiosauroidea clade of plesiosaurs was distinguished by their very long necks and tiny brains. They are collectively known as plesiosaurs after the group's first member, Plesiosaurus. It measured somewhere close to 11 feet long (about 3.5 meters). With a 'flying' motion of the flippers, it glided through the water.
The Pliosauroidea were a clade of plesiosaurs characterized by their short necks and large, heavy skulls. These creatures are also referred to as pliosaurs.
A terrifying pliosaur roamed the Middle Jurassic, and its name was Liopleurodon. This top predator can grow as long as 6.4 meters (21 feet) at maximum size.
Ancient crocodiles also included marine species. Dakosaurus was a saltwater crocodile that lived during the Late Jurassic period. Its maximum height was more than 4 meters (13.12 feet), and it is native to Europe and the Americas.
Metriorhynchus is another example of a type of marine crocodile that lived in the Jurassic period and is represented by fossils discovered in Western Europe.
The Triassic period saw the first appearance of turtles. The two contemporary turtle families, Cryptodira (whose members retract their necks inside the shell) and Pleurodira (whose necks migrate laterally when retracted), both originated during the Jurassic Period.
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