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The Mesozoic Era: Flora and Fauna

"Let’s take a trip to the Mesozoic era and see the various forms of plants and animals that existed in the three periods: the Triassic, Jurassic, and Cretaceous."

Have you ever wondered what living was like in the Age of Dinosaurs? What kind of plants and animals existed along with the ancient beasts? During this era, the earth was very different than what it is now. 

Different types of animals and plants evolved across the three periods of this era, i.e., the Triassic, Jurassic, and Cretaceous. In this post, we’ll explore the various forms of flora and fauna that are said to have existed in the Mesozoic era.

mesozoic fauna flora

Introduction

The Mesozoic Era, commonly known as the Age of Dinosaurs, was about 250 to 66 million years ago and spanned over 180 million years. It is the third era of evolution, after the Paleozoic and the Neoproterozoic eras. Mesozoic saw the emergence of one giant C-shaped landmass on earth called the Pangea supercontinent. 

During the end of the Triassic period, Pangea began drifting apart and splitting into two regions, the Gondwana and Laurasia. The Tethys Ocean separated the two continents. Many life forms evolved in this era, some of which continue to this day. 

Mesozoic Era Flora

Plants are essential for the ecosystem as they’re at the base of the food web. Without them, the herbivore dinosaurs wouldn’t have existed. Plants absorb carbon dioxide and give off oxygen, which helps in changing the composition of the earth’s atmosphere. They also play an essential part in determining the habitats of plant-eating animals. *

As the flora gradually changed, various species of dinosaurs also evolved. Since the meat-eating dinosaurs mostly fed on the plant-eaters, the evolution of plants played a pivotal role in the earth’s atmosphere and the rise of the ancient beasts and various animals. *

Conifers

The dominant flora during the time of the dinosaurs were the coniferous trees and shrubs. These were evergreen and slow-growing and formed the main diet of the herbivore dinosaurs, like the giant sauropods. The conifers mainly included the yews, redwoods, pines, cypress, the monkey puzzle tree (Araucaria), and Pseudofrenelopsis (Cheirolepidiacean). In due course, towards the Jurassic period’s end, flowering plants (angiosperms) became more dominant than the conifers. *

Angiosperms

Angiosperms evolved during the late-Jurassic period, around 140 million years ago. They dramatically changed the earth’s landscape as they quickly spread over most regions in the Cretaceous period. Plant-eating dinosaurs mainly fed on these plants to get their nutrition. Some angiosperms during the Mesozoic were magnolias, barberry, laurel, palms, and early sycamores. *

Cycadophytes

Cycadophytes were plants with tough leaves and woody stems and comprised Cycads and Cycadeoids. Cycads were common in the Jurassic, and we can still see some types today, but the Cycadeoids are now extinct. Some Cycads were Cycas, Dioon, Zamia, Bowenia, Microcyas, Leptocycas, and Stangeria. Some Cycadeoids were Williamsonia, Williamsoniella, Cycadeoidea, Westersheimia, Vardekloeftia, and Leguminanthus. *

Ginkgos

Ginkgos (maidenhair tree) are deciduous gymnosperms usually found in high altitudes. They were found in the Laurasian region in the Triassic but became more widespread during the Jurassic and Cretaceous periods. We can still see them around today. *

Pteridophytes

Pteridophytes include the Lycopods (club mosses), Sphenopsids (horsetails), and ferns. They are primitive vascular plants that reproduce with spores and also using rhizomes. Plant-eating dinosaurs living in moist areas were the primary consumers of the Pteridophytes. Smaller lycopods survived the extinction of the Paleozoic and continued to grow in the Triassic period. Pteridophytes were low-growing during the Mesozoic era and mostly evolved during the Devonian. *

Seed ferns

Pteridosperms (seed ferns) bore seeds instead of spores and had fern-like leaves. They included Caytonia, Dicroidium, Glossopteris, Lidgettonia, and Denkania. Dicroidiums were primarily found in the dry woodlands and forests in the Triassic period when the Archosaurs started to evolve. Pteridosperms were widespread during the Triassic period in southern Pangaea and are now extinct. 

 
mesozoic fauna flora

Mesozoic Era Fauna

The Permian-Triassic extinction event led to the demise of 90% of the marine life forms and 70% of the terrestrial vertebrate species on earth. Various life forms of that time went extinct, like corals, brachiopods, mollusks, echinoderms, and other invertebrates. New species began to evolve along with the few existing ones.

The dinosaurs were the dominant land vertebrates, especially during the Jurassic and Cretaceous periods. Although dinosaurs were the apex predators, there were other kinds of plant-eating and meat-eating animals too in the Mesozoic era, as under: 

mesozoic fauna flora

Reptiles

Reptiles were the dominant vertebrate animals during the Mesozoic era, especially the Triassic. They weren’t just present on the land but also in the air (Pterosaurs) and the sea (Plesiosaurs, Nothosaurs, Mosasaurs, and Ichthyosaurs).

Therapsids, also known as mammal-like reptiles, ruled the Triassic, along with the Thecodonts, ancestors of crocodiles and the dinosaurs. An extinction event happened at the end of the Triassic, leading to the demise of Therapsids and many land vertebrates.  *

The lizards and turtles appeared in the late Triassic. The diapsids also became prominent during the Triassic, the primary group being the archosaurs. Crocodiles also appeared during this period. A marine crocodile, called Deinosuchus, reached over 30 feet in length during the Cretaceous period.

Mammals

The Triassic period saw the appearance of mammals, but they weren’t dominant until the late Triassic. The first mammals were small shrew-sized omnivores during the Triassic. Cynodonts that appeared in the late Permian were also present during this period.

By mid and late Jurassic, some specialized mammals, like burrowers, gliders, and paddle-tailed fish eaters, came into existence. Placentals and marsupials also appeared during the Jurassic period.

Major mammals during the Jurassic and the Cretaceous periods are the Prototheres, Eutriconodonts, Allotheres, Metatheres, and the Eutheres. All except the Eutriconodonts survived the k-Pg extinction. *

Birds

The first birds appeared in the late Jurassic period, and it’s believed that they evolved from the dinosaurs. During the Cretaceous, more birds took flight; among them were Confuciusornis and Iberomesornis. There was also a flightless swimming bird called Hesperornis that lived in water. *

Amphibians

One of the early amphibians that lived during the Triassic was the Triadobatrachus. Frogs, salamanders, and toads evolved during the Jurassic period.  *

Fish

Fishes and sharks swam the Mesozoic seas along with the marine reptiles and invertebrates. Sharks and bony fishes flourished in the Jurassic period. Hybodus was a 6.5 ft long shark that appeared in the Permian period and was there until the late Cretaceous. The marine ecosystem rapidly evolved and diversified during the Jurassic and the Cretaceous periods.

Leedsichthys was a large bony fish, estimated to be about 72 ft long, and was mostly found in the Jurassic period. During the late Cretaceous, Squalicorax, also known as the crow shark, predated other fish and reptiles in the waters. Another large predator said to have lived during the Cretaceous is Xiphactinus, a 20 ft large bony fish. *

Invertebrates

Insects have been present since the Triassic, when they attained complete metamorphosis. The first flies (Diptera) were found in the late Triassic period. The first wasps (Hymenoptera) appeared in the Jurassic that further evolved into the bees and ants in the Cretaceous.

Due to the widespread angiosperms, insects flourished during the Cretaceous and further diversified into bees, butterflies, ants, termites, grasshoppers, and aphids. Moths and butterflies (Lepidoptera) were thriving in the Cretaceous. The beetles, roaches, termites, and mantids diversified during this period.

Mollusks, such as ammonites, gastropods, and bivalves, were among the dominant marine animals. The extinction event of the late Triassic decimated various invertebrates, although the ammonites and brachiopods survived due to the warm seas. The early Jurassic saw the appearance of crab-like crustaceans called the Decapoda. Baculites, a type of cephalopods, were abundant during the Cretaceous. Scaphites were also common ammonites during the late Cretaceous period.

mesozoic fauna flora

From One Era to Another

The Mesozoic era ended with another extinction event called the k-Pg, which decimated almost 75% of all life forms and 90% of the plant-like and animal-like planktons, including the ammonites, rudist bivalves, and marine reptiles. The flying reptiles and the dinosaurs also became extinct. However, some species of plants and animals survived and evolved further. 

The angiosperms continued to survive as they went through adaptive radiation. Among many others, frogs and salamanders also made it to this era. So, next time you look at a monkey puzzle tree, let it take you to a time millions of years ago when the air was fresh and the planet wild and free.

Ekta G

Ekta G

Writer

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