It is called the age of reptiles.

The era began in the wake of the Permianā€“Triassic extinction event, the largest well-documented mass extinction in Earth's history, and ended with theCretaceousā€“Paleogene extinction event, another mass extinction which is known for having killed off non-avian dinosaurs, as well as other plant and animal species. The Mesozoic was a time of significant tectonic, climate and evolutionary activity. The era witnessed the gradual rifting of the supercontinent Pangaeainto separate landmasses that would eventually move into their current positions. The climate of the Mesozoic was varied, alternating between warming and cooling periods. Overall, however, the Earth was hotter than it is today. Non-avian dinosaurs appeared in the Late Triassic and became the dominant terrestrial vertebrates early in the Jurassic, occupying this position for about 135 million years until their demise at the end of the Cretaceous. Birds first appeared in the Jurassic, having evolved from a branch of theropod dinosaurs. The first mammals also appeared during the Mesozoic, but would remain smallā€”less than 15 kg (33 lb)ā€”until the Cenozoic. -Wikipedia, Mesozoic

Keep readingā€¦

INVERTEBRATE LIFE IN the seas slowly recreated itself. Those surviving species radiated and established the new character of Mesozoic oceans. The ammonoids, surviving only as two species, expanded into 150 species. This slow expansion through adaptive radiation was a move typical for the surviving gastropods as well as bivalve mollusks, brachiopods, crinoids, urchins, and sponges. Gone forever were the trilobites, the fusulinid foraminifers, the lacy bryozoans, and the rugose corals. Replacing these were new creatures such as the hexacoral that would eventually join in the reef-building, the coccolithophores, an algae that filled the seas, and the belemnoids, squidlike mollusks without an external shell. The vertebrate world of the Mesozoic was radically new. Two novelties appeared near the transition from the Paleozoic to the Mesozoic that altered the character of terrestrial animal life. The first crucial invention was the amniotic egg, which freed terrestrial amphibians from their depen-dence on bodies of water for their mating processes. The egg, protected from the environment by a more or less impervious shell during the period of the embryo's development, is completely self-sufficient, requiring only oxygen from the outer world. The beings who created the eggs were the first reptiles. They could now deposit their eggs far from the predators who patrolled the shallow waters in search of fertilized eggs. As their skin grew more watertight the reptiles could roam far inland, even into deserts. Amphibians could never reach such regions, for their permeable skin would give way under any prolonged heat, leaving them desiccated. But now the reptiles with their eggs had Found a way to continue the adventure into the dry valleys, up into the hot mountains, out into the endless Sun-baked plains. The reptiles crowded out the amphibians to become the predominant terrestrial vertebrate. Just as the naked seed plants, better adapted to the drier conditions far from the sea, populated the continents and became the principal plant life in the late Paleozoic and early Mesozoic, so too, the rep-tiles, better adapted to the challenges of the dry climate far from the oceans and lakes, populated the continental land masses, especially after the ex-tinction spasm that inaugurated the Mesozoic. The second great invention of the terrestrial animal world was endothermy, the power to maintain a warm body even in the face of a cold outer world. The therapsids were the first to enjoy this new capability. Now able to sustain high activity through prolonged periods, even when the Sun was blocked out on a cloudy day, such "warm-blooded reptiles" altered the his-tory of life. The legs of the amphibians and early reptiles came out at an angle, making a crouching posture necessary for their movements. But therapsid speed demanded appropriate anatomical changes and soon their legs were rotated beneath them, enabling a much higher velocity of loco-motion. Over the first million years of the Mesozoic, the swift therapsids quickly devoured their way to the top of the food chain, acquiring an even more powerful snapping jaw along the way. Reptiles also took to the seas. Seal-like placodonts with their shell-crushing teeth discovered their niche when they learned to feed on the rich molluscan life on the sea floor. The nothosaurs also lived along the shore-lines and fed in the shallows. The speedy ichthyosaurs competed directly with the fish and sharks when they learned to venture far from land by giving birth not to the amniotic egg but to the live, baby ichthyosaurs. The plant world was not decimated by the Paleozoic mass extinctions in the way the animal world was. The transformation of the forests from lycopod to naked seed plants continued through the terminal Permian as well as into the Mesozoic. The most common types were the conifers, the cycads, the gingkos, as well as the spore-bearing ferns that proliferated beneath the canopies of these gymnosperm forests.

THE GREATEST MESOZOIC creativity among the terrestrial vertebrate world was the dinosaur, a further development of the warm-blooded reptilian line of therapsids and thecodonts. Dinosaurs ranged in size from a couple of feet to a hundred feet in length. Many of them benefited from the anatom-ical modifications of their ancestors, and with their quick movements they soon replaced the lizards in many niches. For one hundred million years dinosaurs were the most prevalent vertebrate form. They were social ani-mals that often traveled and hunted in groups. And dinosaurs developed a behavioral novelty unknown in the reptilian worldā€”parental care. Dinosaurs carefully buried their eggs and stayed with the young after they hatched, nurturing them toward independence. In the middle of the Mesozoic era the first bird appeared, 150 million years ago, a direct descendent of the dinosaur. Birds retained as well the endothermy and the parental care of the dinosaurs. Somewhat later, 125 million years ago, the first marsupial mammal appeared. These mammals shared with the dinosaur such things as vertebrate anatomy, warm-blooded metabolism, and parental care, but differed in having body fur instead of dinosaur scales, giving live birth instead of laying reptilian eggs, and nurs-ing their young, rather than having independent young. The new mammalian mode of nourishing the young in the earliest pe-riod of their existence outside the womb was immensely significant for the future psychological formation of the mammalian species. This bodily intimacy during pregnancy and after birth can be associated with the distinctive emotional qualities that develop in this line of descent. Mam-mals remained small and probably nocturnal throughout the rest of the Mesozoic. Other vertebrate novelties of the Mesozoic included the turtles, the crocodilesā€”both of which reached huge proportionsā€”and the frogs. The greatest Mesozoic creativity in the plant world was the flower in Cretaceous times. The sexuality of the flowering plants (angiosperms) was an order of magnitude more fecund than that of the gymnosperms. Where a conifer would require eighteen months to produce its seeds, a flower could grow from a seed to a mature plant capable of releasing its own seeds, all in a few weeks. Added to its fecundity was the symbiotic rela-tionship between the insect world and the flower. Insects drawn to the nectar unknowingly transport pollen from one flower to the next, fertiliz-ing the plants on which they feed. Often a particular insect will feed only on a particular flower, thus assisting in the process of creating a new spe-cies. If a new shape of flower appears, it may draw a different kind of insect, thus isolating this new flower from sexual contact with its original group. In this way new kinds of insects create new kinds of flowers. The flowering plants quickly diversified and spread throughout the continents. Their eco-logical success depended on such intricate symbioses, in what is some-times called a survival of the most cooperative. With the expansion of the flowering world came the proliferation of the insects, and such changes worked themselves back into the vertebrate world with amazing consequences. Dinosaurs had evolved to feed on the gymnosperms, but the flowers were now pushing gymnosperms out. Birds and mammals, on the other hand, fed happily on the flowers and their seeds, and on the symbiotically aligned insects, all of which enabled the birds and mammals to flourish while the dinosaurs declined. -Brian Swimme and Thomas Berry, The Universe Story, p120-123.

THE MESOZOIC WORLD of sea reptiles and dinosaurs was ripped apart 67 THE years ago by what was perhaps the fourth most devastating mass extinctionā€”the terminal Cretaceous. Eliminated forever were the many and diverse forms of dinosaurs, marine reptiles, ammonoids, many rudists, and bivalve mollusks. The coccolithophore algae that had predominated would never again attain such a planetary presence. Earth grew cold and the Cenozoic era began with an impoverished fauna. In the devastated world of the early Cenozoic, an animal invention of the previous era exploded into many different forms. About 114 million years ago the first placental mammals had appeared. By giving birth to live young, the placental mammal had the advantage of an offspring that began its life at a more advanced form than the offspring of either the reptiles or the dinosaurs. By itself, this invention would not have made much differ-ence in a Mesozoic dominated by the dinosaur, but combined with the mass extinction that depleted the fauna and eliminated the competition, placental mammals increased to become the prominant vertebrate form of the new Cenozoic era. The Cenozoic is a time of stupendous creativity. Within twelve million years of the Cretaceous mass extinction most of the living orders of mam-malsā€”including bats and whales and primatesā€”had already entered ex-istence. This period represents only 2 percent of the mesocosm's history. Thus in a geological instant the placodonts, the nothosaurs, the plesio-saurs, the ichthyosaurs, the mesosaurs, the tyrannosauruses, the bronto-sauruses, and the triceratops gave way to the Cenozoic's newly createdā€¦ Check the next section under Cenzoic -Brian Swimme and Thomas Berry, The Universe Story, p123

Mesozoic db