The end of the dinosaurs is one of the greatest mysteries of paleontology. The leading theory of their extinction involves a massive meteor impact, possibly the one that created the Chicxulub crater in Mexico. Alternative theories include multiple global impacts, a sudden change in the sea level and a worldwide increase in volcanic activity that drastically altered the atmosphere and global climate.Continue Reading
According to the Alvarez Hypothesis, the extinction of the dinosaurs occurred as a result of a massive comet or meteor impact. One of the major pieces of evidence that supports this hypothesis is a layer of iridium found in clay that marks the boundary between the Cretaceous and Paleogene periods, which is when the dinosaurs went extinct. In the 1990s, geologists discovered a 112-mile-wide crater just off the Yucatan peninsula that provided evidence of just such a massive impact occurring around the same time as the extinction.
A few questions remain unanswered, however. A single impact would have had devastating effects on the environment, but most of the dangerous changes, such as an increase in acid rain, would only last a decade or two after the event. The dinosaurs' extinction occurred over a more extended period of time, bringing up the possibility that multiple impacts, possibly including the one that caused the Shiva crater in India, may have contributed to the extinction.Learn more about Dinosaurs
The first true dinosaurs first appeared about 230 million years ago. The first dinosaur fossils are distinguished from those of their reptile ancestors by their more upright stance, with legs directly beneath the body instead of splayed to the side, as with other reptiles. The earliest dinosaur fossils were found in South America, although a December 2012 fossil discovery in southern Africa casts some doubt on a South American origin.Full Answer >
Beginning in 1887, dinosaurs have been divided into two main categories: saurischian, which means "lizard hipped," and ornithischian, which means "bird hipped." This classification is based on the dinosaurs' pelvic bone structure. Though the name "bird hipped" may seem to indicate that these prehistoric animals are related to birds, that is not necessarily the case.Full Answer >
The Tyrannosaurus rex was a carnivore and one of the largest meat-eating dinosaurs on Earth. It could consume nearly 500 pounds of meat in a single bite. The term "tyrannosaurus" means tyrant lizard.Full Answer >
Types of dinosaurs include the apatosaurus, the anklyosaurus and the stegasaurus. The apatosaurus was a plant-eating dinosaur that lived during the Jurassic Period, between 115 to 150 million years ago.Full Answer >