The mighty dinosaurs, although almost lost to history, seem to have a powerful influence on people’s imaginations in ways that no other animal can do. They have dominated the land of the planet for over 150 million years. They have grown larger than any other land animal in Earth’s history. And they have been intertwined with the fields of paleontology, geology, and evolution from the very beginning. But how long have dinosaurs been on earth? We have covered this in detail.
The scientific study of non-avian dinosaurs dates back to the 1820s, when William Buckland became the first person to describe it in a scientific journal. The term “dinosaur” itself was coined by British paleontologist Richard Owen in 1841. The name comes from a combination of the Greek words deinos (meaning terrible or terribly great) and sauros (meaning lizard or reptile).
Dinosaurs belonged to a group of animals called archosaurs, of which birds and crocodiles are the only living members. This group also included the extinct now-flying pterosaurs and the crocodile-like Etosaurs, among others. There are several traits that differentiate dinosaurs from other archosaurs, including specially modified vertebrae called the sacrum, which connect the hip and spine together. A dinosaur usually has at least three of these structures. Combined with modifications to the femur, knee, and ankle, early dinosaurs were able to achieve a form of bipedal movement, in which their legs were tucked directly under the body, although many species later evolved back to a quadrupedal position.
Soon after the dinosaurs were discovered, scientists began piecing together a more complete history of the group. They soon developed a system in which the entire history of dinosaurs, from their evolution to their extinction, fits neatly into the Mesozoic era between 250 and 66 million years ago. The Mesozoic consists of three different periods: Triassic, Jurassic and Cretaceous. This article will take a closer look at all three periods.
How long have dinosaurs been on Earth? – Triassic period
Dinosaurs first appeared during the Middle to Late Triassic period, approximately 230 to 240 million years ago. It was a time of great fermentation and change. After the mass extinction 250 million years ago, which wiped out most of the living species on the planet, several new and distinctive forms have emerged, including the first ever flying vertebrates, the pterosaurs. It was also the last time the continents were united into a single continent called Pangea.
Despite everything we know about dinosaurs, their actual evolutionary origins are still shrouded in mystery. The earliest dinosaurs were believed to be relatively small and bipedal reptiles, at least partially carnivorous in nature, with small, grippy hands. The closely related Lagosuchus and Lagerpeton, which, although similar, were not real dinosaurs in the pure sense of the word, probably represented what they looked like. Instead, the first true dinosaurs to appear in the fossil record were animals such as the small bipedal eoraptor and the larger Herrerasaurus.
By the end of the Triassic period, dinosaurs occupied a unique niche in the ecosystem. They were still evolving in new forms and were still spreading around the world. However, their fate will soon change when another mass extinction occurs, possibly caused by volcanic activity or an asteroid collision that ended this period about 201 million years ago. This event wiped out many of the oldest archosaurs, but dinosaurs survived and became the dominant life form during the Jurassic period.
How long have dinosaurs been on Earth? – Jurassic period
The Jurassic period, which lasted from 201 million to 145 million years ago, is most often associated with dinosaurs in the popular imagination. This period was marked by a warming climate and the split of Pangea into several continents. As a result, during this period, dinosaurs significantly diversified and became one of the most common animals on the planet. While the earliest mammals were small, rodent-like creatures still scurrying about the earth, many dinosaur species were massive in both size and height (although this was partly the result of the preservation of fossils; the largest fossils are likely will be saved and discovered). The large carnivorous Allosaurus, the long-necked herbivorous Brachiosaurus, the armored ankylosaurus, and the pointed stegosaurus all lived and flourished during this important period in dinosaur history. Horns, ridges and frills will flourish and diversify as visual communication tools.
Another important evolutionary innovation of the Jurassic period was the feather. Feathers, which emerged from a very simple thread-like structure, first appeared in the fossil record about 180 million years ago, although they were limited to certain groups such as Deinonychosauria. Feathers may have originally served for thermal insulation, communication, or water repellency. When birds first began to develop into a separate class during the Jurassic period, feathers soon began to adapt for flight as well. Archeopteryx, which was capable of only limited flight or gliding, was one such early example of birdlike ancestors.
Since the closest living relatives of dinosaurs, the flying pterosaurs, were also sometimes covered in feathers, some experts suggest that feather evolution dates back to their last common ancestor in the Triassic period about 250 million years ago. However, there is no direct evidence that the earliest dinosaurs possessed feathers at all. This means one of two possible explanations: either early feathered dinosaurs have not yet been discovered, or feathers arose separately in dinosaurs and pterosaurs after they split from each other (this phenomenon is known as convergent evolution).
How long have dinosaurs been on Earth? – Cretaceous period
The Cretaceous Period, which lasted between 145 and 66 million years ago, was the last and, in a sense, the greatest period of dinosaur dominance. By this point, the continents had divided into separate land areas, and although the climate had cooled slightly, most of the planet was still covered with dense forests all the way to the poles. This has led to the emergence of many unique forms of dinosaurs around the world. Triceratops, Utaraptors, Iguanodons, Duck-billed Hadrosaurs, Tyrannosaurs, and Amargasaurs (which had parallel rows of spines on their neck and back) lived in the Cretaceous (and not, as is commonly believed, in the Jurassic period).
The Cretaceous period also marked the dominance of the largest land animal in history, the long-necked dreadnought, which weighed about 65 tons and reached 85 feet from head to tail. Along with the equally large Argentinosaurs and Saltasaurs, he belonged to a group of herbivorous dinosaurs called titanosaurs. The appearance of flowering plants during this period greatly influenced the evolution of herbivorous dinosaurs and the more sophisticated way of eating and digesting them.
Spurred on by an evolutionary arms race, dinosaurs grew larger, faster, and stronger during this period. The closely related Gorgosaurus and Albertosaurus were massive bipedal predators that stalked North America, feeding on very large animals such as hadrosaurs. However, there were also larger contenders. Spinosaurus, which had rows of bony spines on its back and a crocodile-like mouth, was a semi-aquatic dinosaur that hunted both fish and land animals.
Supposedly slightly larger than a Tyrannosaurus (although estimates do vary), it competed with the equally impressive South American beast, the Giganotosaurus, for being the largest land-based predator in history at 40 to 60 feet in height. While some species have succeeded in being as small and inconspicuous as possible, it seemed that many dinosaurs were struggling with physical size limitations.
How long have dinosaurs been on Earth? – Extinction
At the end of the Cretaceous period, the era of the dinosaurs ended in a disastrous way. About 75% of all plant and animal species on the planet, including the remaining dinosaurs, became extinct as a result of an asteroid impact about 66 million years ago. Having crashed into the planet with a force of 180 trillion tons in TNT equivalent, the asteroid threw out a huge amount of ash into the atmosphere, which interrupted the photosynthesis of plants for several years. Most large animals weighing over 50 pounds soon became extinct. Whether the extinction of non-avian dinosaurs was sudden or gradual remains an open question that has not yet been decided. However, avian dinosaurs (birds) were the only lineage that survived this period.
Will scientists be able to revive dinosaurs again? In a sense, the answer is no. Since DNA degrades over time, scientists have never been able to reconstruct dinosaurs as they actually existed. There is simply too much we will never know about them. But some scientists have proposed a way to reconstruct a dinosaur from a bird, perhaps creating a modern version of an ancient reptile that still thrives in the imagination.