How many dinosaurs existed

Multimedia Gallery. Park Passes. Technical Announcements. Employees in the News. Emergency Management. Survey Manual. Dinosaurs went extinct about 65 million years ago at the end of the Cretaceous Period , after living on Earth for about million years. If all of Earth time from the very beginning of the dinosaurs to today were compressed into days one calendar year , the dinosaurs appeared January 1 and became extinct the third week of September.

Using this same time scale, the Earth would have formed approximately Using the same scale, people Homo sapiens have been on earth only since December 31 New Year's eve. The dinosaurs' long period of dominance certainly makes them unqualified successes in the history of life on Earth.

DescriptionThis bookmark presents information that is widely sought by educators and students. This bookmark is adapted from the more detailed U. Geological Survey USGS researchers are at the forefront of paleoclimate research, the study of past climates.

With their unique skills and perspective, only geologists have the tools necessary to delve into the distant past long before instrumental records were collected in order to better understand global environmental conditions that The Earth is very old - 4. Most of the evidence for an ancient Earth is contained in the rocks that form the Earth's crust.

The rock layers themselves - like pages in a long and complicated history - record the events of the past, and buried within them are the remains of life - the plants Effective communication in the geosciences requires consistent uses of stratigraphic nomenclature, especially divisions of geologic time.

A geologic time scale is composed of standard stratigraphic divisions based on rock sequences and calibrated in years. Over the years, the development of new dating methods and refinement of previous ones have At the close of the 18th century, the haze of fantasy and mysticism that tended to obscure the true nature of the Earth was being swept away.

Careful studies by scientists showed that rocks had diverse origins. Some rock layers, containing clearly identifiable fossil remains of fish and other forms of aquatic animal and plant life, originally The Tertiary is a system of rocks, above the Cretaceous and below the Quaternary, that defines the Tertiary Period of geologic time. Four years ago, a bulldozer operator turned over some bones during construction at Ziegler Reservoir near Snowmass Village, Colorado.

Geological Survey scientists with a laboratory to study more than , years of vegetation and climate records in Colorado. The urban bedrock of a low-relief landscape beneath a crowded city seems like an unusual place for a significant fossil discovery.

To this day, there has been no other species that has dominated the world for so long, not even humans, which indicates that this species had an unusual development and survival capacity, although due to a meteorite its story ended. If it were not for that, surely the human being would not have existed and, in the event that it were, would not be the dominating animal of the planet.

To give you an idea, imagine living with the Tyranosaurus Rex, Gigantosaurus or the Spinosaurus; we would be their favorite delicacy, they would hunt us with great ease and we would not have been able to rise to the occasion. Therefore, we should be grateful for the disaster that occurred at the time. However, this was not the main issue, but how many dinosaurs existed.

They are believed to have been fast running carnivores, probably feeding on smaller lizards. They had an elongated snout with large openings that reduced the weight of their skull.

The curvature of their necks allowed for a quick biting movement. This dinosaur lived at the end of the Jurassic era. The main characteristic of these animals was the horn-shaped structure on their skull, behind their nostrils, and two more horn-shaped ridges in front of their eyes.

This was one of the few theropods that had armoured skin, in the the form of small bony plates. Its tail measured half its total length and its back was lined with vertebral spines. They lived in modern-day United States, Tanzania and Europe and it was one of the first dinosaurs to be discovered.

The name Monophosaurus refers to the ridge on top of its skull. It ran from between the nostrils up to the eyes. It was hollow inside and may have been used to attract females during the mating season. It is a species of Carnosaurus that lived in Asia at the end of the Jurassic era. It was up to 6 meters long and 2 meters high and had very sharp teeth. Remains of this species have always been found close to water, suggesting that they may have inhabited areas near lakes or oceans.

This species lived in North Africa during the Cretaceous period. The Spinosaurus was the largest of all the carnivorous dinosaurs. It could measure up to 18 meters in length and weighed in excess of 20 tons. They had a skull similar to that of a crocodile and spikes measuring up to 1. Covered and joined together by skin, they would have been used for both thermoregulatory and display purposes.

They walked on all fours most of the time and it is believed they spent a lot of time in the water, feeding on fish. The Allosaurus is a theropod that lived at the end of the Jurassic period. They were large up to 9 meters long , bipedal and had strong claws and sturdy legs. They used their long, heavy tail to balance as they moved.

Their skull was relatively large and featured two ridges in front of and above the eyes. Despite their large size, these predators were relatively light. Their teeth were serrated, but not very big, and it is believed that they hunted by stalking their prey and striking them hard with their jaws. These small reptiles lived during the end of the Jurassic era.

They were carnivores that fed on small lizards. They had long hind legs, a long tail to maintain their balance, an elongated skull with a pointed nose, small serrated teeth and relatively large eyes. The T-Rex lived at the end of the Cretaceous period. It was one of the last dinosaurs around before the great extinction, as well as being one of the largest predators to have set foot on our planet.

It was bipedal, with strong hind legs, an enormous skull, a long and thick tail for balance. It possessed small but strong front legs, equipped with two clawed toes. Experts are still debating whether they were hunters or scavengers. According to the latest studies, the T-Rex appears to have been covered with feathers like many other dinosaurs. They were more than 3 meters tall and inhabited part of the current United States during the end of the Cretaceous.

Their bones were hollow which made them lighter, possibly allowing them to run faster. There have been plenty of remains found of this species, which would suggest that they were not carnivores, and the hypothesis is that they lived in herds.

They had no teeth and their snout was more like a beak. They may have been covered with feathers. These dinosaurs inhabited the Gobi Desert at the end of the Cretaceous. They measured 1 meter and weighed about 3 kilograms. They had strong hind legs and were fast, highly agile runners. Their front legs were very short and had just one finger, ending in a long claw. Supposedly, these animals were covered with feathers.

Their small skull, contained little, sharp teeth. They are believed to have eaten insects and small animals, and that they hunted at night, like the Velociraptor, thanks to their specially adapted eyes. Among the individual bones unearthed of this dinosaur were its enormous, 70 cm long claws. It was estimated to be 8 to 12 meters long and weighed up to 6 tons. As the fossil record of life is vastly incomplete, we can only guess that many, many more species existed - but we might never find their fossil remains.

At least we know that many new dinosaurs will continue to be found as expeditions keep going out searching for them every year. Who knows - maybe one day you will be part of an expedition that discovers a new dinosaur.

If you found a new dinosaur, what would you name it? Read more: Curious Kids: Why do birds sing? Hello, curious kids! Ask an adult to send your question to us. They can:. Please tell us your name, age, and which city you live in.