The Thriving Titans
The rise of the Jurassic Era was nigh when the Triassic period ended as it had begun: a mass extinction caused by theories of an asteroid collision with Earth, climate change [Yes Donald, its real], or volatile and massive volcanic eruptions. With 34% of marine life eradicated, and the majority of the Archosaurs exterminated, life on Earth took a huge blow. However, the recovery was quick compared to the last extinction [The Great Dying] and life began to thrive again. The world encountered masses of diversifying life, ranging from the common but first large land meat-eating dinosaurs Allosaurs to the gigantic long-necked Diplodocus!
The only Archosaurs that survived were the Crurotarsi and the Onithodira, along with some Therapsids and many Amphibians. The Jurassic Era lasted from 199.6 million to 145.5 million years ago. During this Era, the splitting of the Pangea occurred and resulted in the birth of two large lands: Laurentia [the northern half] and Gondwana [the southern half]. However both Laurentia and Gondwana themselves also began to separate into huge landmasses, with Laurentia splitting into what we now know today as North America and Eurasia, and Gondwana splitting into Antartica, Madagascar, India and Australia in the East and Africa and South America in the west.
As a result of these segregations of lands, combined with the higher global temperatures it allowed for the fluctuation of new and diverse species dinosaurs. Reptiles that existed in the Jurassic, had overcome the evolutionary curb of reproduction and support in which the amphibians could not prevail over. These reptiles known as Dinosaurs had strong and proficient skeleton structures complemented by their powerful muscles provided support and efficient mobility. Instead of giving birth like us humans do, very much like the modern birds, Dinosaurs all laid amniotic eggs, which allowed them to be nourished and provided the essential nutrition and moistness to support the unborn dinosaurs during gestation [the carrying of an embryo].
In the Jurassic, there were two main types of land-dinosaurs that roamed the Earth which Sauropods and the Theropods. Sauropods [meaning lizard-foot] were quadruple legged, titan-sized dinosaurs and comprised of extremely long necks, long tails but small heads and thus they had small brains. Being herbivorous, they ate a variety of plants and conifers but rather than chewing their foods, they swallowed whole branches and stems of those plants!
This is due to the anatomy of their skulls and peg-like teeth, which would not grant them the ability to chew. However, this disadvantage gave them the ability to intake large amounts of foods as mentioned above, allowing them to grow to their incredible sizes such as the Brachiosaurs, Diplodocus, and Brontosaurs etc. These Sauropods were absolutely titanic, with some having lengths of 30m+ like the Diplodocus, and most weighing more than 20 tons.
However, with such large herbivores existing in the Jurassic, it would make sense that they were accompanied by large predators too. Generalised as ‘Carnosaurs’ [defined as meat-eating dinosaur]’, these were the terrestrial apex predators of the land dinosaurs known as Theropods. In the Early Jurassic, these bipedal Theropods [meaning beast-footed] were small and were light-weighted providing much agility and speed. However, with prey such as the Brontosaurs, these ravenous Carnosaurs adapted, growing into gigantic predators such as the Allosaurs and Ceratosaurs.
These predators, were heavy supported by incredibly powerful hind legs used their powerful jaws and grasping front limbs as means to tear and shred herbivores and even other Carnosaurs apart. However, these Carnosaurs would not go head to head with those titanic herbivores due to their obviously incredible sizes. One step from those titans would crush even those large predators, and thus they were very opportunistic; always going for the young, weak, old or injured. These beasts were truly fearsome survivors and would even clash with the most defensive herbivores such as the Stegosaurs, which were armed with tough and triangular plates [which also aided thermoregulation] along with their backs as well as spiked tails to drive off or even kill their predators, just to have them as their delicacies.
Plant life also diversified too, having Ferns and Gingkoes that had spore reproduction systems as well as roots and vascular systems to allow the transport of nutrients as water, and later on in the Jurassic, Gymnosperms which were cone-bearing plants that reproduced through wind pollination, allowing them to grow almost everywhere. Marine life also developed, with the rise in prominence of sea predators known as the Plesiosaurs. These Plesiosaurs had long necks and four flippers and were carnivores that feasted on squids, fishes and molluscs.
Ichthyosaurus still flourished in the early Jurassic since the Triassic. However, mammals on land were very small despite the large diversifying that the Jurassic had undergone. They were often herbivores, insectivores or frugivores [fruit-eaters] and were nocturnal, possibly a means to reduce the competition with Dinosaurs.
This Era truly was the time of the Dinosaurs, as they dominated the land, over mammals and heavily populated the Earth. However, if you think they were massive, be prepared to learn about their far larger cousins in the Cretaceous Era!