With a standing population of 20,000 of the dinosaurs, and with some 127,000 generations of the species, there would be 2.5 billion dinosaurs overall, the team determined.
Using this new method, applied to the whole known dinosaur record through the whole of the Mesozoic (Triassic to the end of the Cretaceous), they estimated that 1543-2468 species existed altogether around the globe.
Over a total of about 127,000 generations that the species lived, that translates to about 2.5 billion individuals overall.
After the dinosaurs died out, nearly 65 million years passed before people appeared on Earth. However, small mammals (including shrew-sized primates) were alive at the time of the dinosaurs.
Given uncertainties in the creatures' generation length, range and how long they roamed, the Berkeley team said the total population could be as little as 140 million or as much as 42 billion with 2.4 billion as the middle value.
The age immediately prior to the dinosaurs was called the Permian. Although there were amphibious reptiles, early versions of the dinosaurs, the dominant life form was the trilobite, visually somewhere between a wood louse and an armadillo. In their heyday there were 15,000 kinds of trilobite.
The Permian is a geological record that began nearly 300 million years ago, almost 50 million years before the Age of the Dinosaurs. During the Permian the first large herbivores and carnivores became widespread on land. The Permian ended with the largest mass extinction in the history of the Earth.
God told Noah, “And of every living thing of all flesh, two of every sort shalt thou bring into the ark, to keep them alive with thee; they shall be male and female” (Genesis 6:19). A few small dinosaurs would have been on the ark. The larger species of dinosaurs were probably young and smaller on the ark.
Yes, birds are the closest living relatives of the dinosaurs because of several shared characteristics: Lay eggs: Like birds, dinosaurs built nests in which to lay eggs. Their young would hatch from these eggs. This way of reproduction is called oviparity.
They would still probably be small, scrawny, and very generalized. But instead, the mammals were able to evolve and diversify and, well, ultimately, millions of years later, become some humans. So perhaps we would not have been here if it weren't for this extinction event 65 million years ago.
As evidence suggests that many dinosaurs had metabolisms more like birds, they probably did not have the same relative life spans as large reptiles. It is possible that sauropods reached 50-100 years, large theropods a bit less and smaller dinosaurs could live to about 10 or 20.
Evidence suggests an asteroid impact was the main culprit. Volcanic eruptions that caused large-scale climate change may also have been involved, together with more gradual changes to Earth's climate that happened over millions of years.
Crocodilians are the most closely related group. They evolved before dinosaurs and experts put crocodiles in the larger family group, archosaurs. Strictly speaking, birds are the only direct descendants of the giant, extinct dinosaurs, and crocodiles and alligators are close relatives.
Bones of primitive Homo sapiens first appear 300,000 years ago in Africa, with brains as large or larger than ours. They're followed by anatomically modern Homo sapiens at least 200,000 years ago, and brain shape became essentially modern by at least 100,000 years ago.
These studies, done in conjunction with paleontologists at AMNH, document that that Tyrannosaurus, which attained a weight of more than 10,000 pounds as an adult, reached sexual maturity at about 20 years of age and lived for up to 28 years.
They existed long before our time, and there are no dinosaurs left today.
So, it's not currently scientifically possible to bring back a dinosaur.
Alligators & Crocodiles: These sizeable reptiles survived–even though other large reptiles did not. Birds: Birds are the only dinosaurs to survive the mass extinction event 65 million years ago.
What Survived and How? Believe it or not, some animals and other organisms survived the mass extinction. Crocodiles, small mammals, and even some tenacious plants, for example, managed to live on after the asteroid impact.
According to Dr. Jordan Mallon, paleontologist and research scientist at Canadian Museum of Nature, dinosaurs had varying diets: some ate plants, some ate meat, and some ate both, but most were actually plant eaters. “If every dinosaur were a meat eater, their environment would be unable to support them,” he says.
To discover how organisms lived in the past, paleontologists look for clues preserved in ancient rocks—the fossilized bones, teeth, eggs, footprints, teeth marks, leaves, and even dung of ancient organisms. Fossilized jaws, teeth, and dung provide important clues about what non-avian dinosaurs ate.
Paleontologists don't know for certain, but perhaps a large body size protected them from most predators, helped to regulate internal body temperature, or let them reach new sources of food (some probably browsed treetops, as giraffes do today).
The earliest evidence of shark fossils dates back as far as 450 million years, which means these creatures have been around at least 90 million years before trees and 190 million years before dinosaurs.
The earliest life forms we know of were microscopic organisms (microbes) that left signals of their presence in rocks about 3.7 billion years old.
Around 240 million years ago, during the Cretaceous period, the earth looked pretty different. It was a time when dinosaurs roamed freely and crocodiles coexisted alongside them. In fact, crocodiles are one of the only animals that are thought to have survived the asteroid that wiped out the dinosaur population.