Who were the first inhabitants of America? Two hundred and twenty-five million years before the Native Americans lived in America, dinosaurs ruled the Earth. Dinosaurs lived here longer than any other land creatures in the history of Earth, for over 150 million years. Humans by comparison have been around only between 2-3 million years.
Dinosaurs were first discovered and named in 1842 by Sir Richard Owen. The name really means "Fearfully-Great Lizard," not "Terrible Lizard." Our understanding of dinosaurs has evolved over the past hundred and fifty years. We first thought that dinosaurs were slow moving, cold-blooded reptiles who were too stupid to adapt to changing weather. Nowadays some modern paleontologists (scientists who study dinosaur bones) think that dinosaurs were intelligent creatures that cared for their young.
One of the most respected paleontologists is Dr. John "Jack" Horner, from Montana State University. Jack Horner found his first fossil at age 8, and has been searching for more ever since. His underground laboratory/storage facility beneath the Museum of the Rockies in Bozeman, Montana contains the largest dinosaur bone collection on Earth. Right now he is working on a third Jurassic Park movie with Steven Spielberg. He cannot tell us any of the secrets about that movie, but what he has to say about dinosaurs is truly amazing!If you look out your window right now, you might see a direct descendent of dinosaurs: according to most scientific evidence, the dinosaurs live on today as birds. Scientists even classify birds as non-avian dinosaurs, or therapod dinosaurs. The theory is that the scales on the dinosaur extended into feathers. There are also many similarities in the eggs and skeletons of birds and dinosaurs, and there are even fossils of transitional creatures with both kinds of features. Fossils have been found in almost every single state, but most of them have been found in Montana, Colorado, and parts of Wyoming. Dinosaurs like the Tyrannosaurus Rex were thought to be indigenous to North America, and so far this holds true, as no other T-Rex's have been found anywhere else on Earth.
In Montana, Jack Horner has found T-Rex's, Saber Tooth Cats, and his all-time favorite, the Duck-Billed dinosaur. He believes that the Duckbills cared for their babies. Some of the evidence for this theory lies in the remains of baby duckbill skulls, which are shorter and rounder than full-grown skulls. The idea is that like mammals who require long term attention, baby Duckbill dinosaurs looked vulnerable and cute with big eyes to keep the parent's attention.
There is a giant debate still going on between scientists about how dinosaurs kept their bodies warm. The real question is whether dinosaurs were endothermic or exothermic. Endothermic means that they produced their own body heat, while exothermic means that they relied on the outside environment to provide them with warmth. There are many arguments that go against both theories, so the most widely-accepted hypothesis right now is that they were "dinosaur blooded." In other words, some dinosaurs produced their own heat, while others relied on outside temperature. Scientists will get a clearer picture of how dinosaurs kept themselves heated once they figure out the evolution of modern endo- and exothermic animals.
Of course, the most sought-after question about the dinosaurs is this: What brought an end to such long-lasting creatures after 150 million years of existence? It is an important question to study, because if mass extinction could happen to them, the same thing could also happen to us. Scientists all agree that there was a gigantic climatic change. What scientists do not agree on is how that change happened. We do know that before most of the land animals became extinct, many sea animals also started dying off. The continents were shifting and colliding at this time, which raised many volcanoes and released tons of soot and greenhouse gases into the air.
Around 65 million years ago, at the barrier between the Cretaceous and Tertiary period, a very dramatic event happened that killed 60% of all forms of life on Earth. One theory, called the Alvarez Hypothesis, is that a sixty five mile-wide comet hit the Earth near Chicxulab, Mexico, which is located on the Yucatan peninsula. This comet raised up so much dust, that a very long winter set in that finished off many creatures who had been struggling from climate changes caused by shifting continents.
These mass extinction events occur about once every 26 million years. Coincidentally, a group of comets called the Oort Cloud pass by our solar system every 26 million years, and it is possible that each time it passes it sends a barrage of comets down on Earth. The biggest mass extinction ever recorded occurred between the Permian and Triassic period. When that event happened, 90% of life on Earth died.
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