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.Know More
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 in Dinosaurs
There are a few well-researched theories about why dinosaurs are extinct; one of the most prominent theories hypothesizes that a massive asteroid impact killed off the dinosaurs. Another states that heavy volcanic eruptions across the Earth may have been responsible.Full Answer >
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 >
There are some animals on earth that can be traced back to the Mesozoic Era when dinosaurs walked the earth; these animals include monotremes such as the duckbill platypus, reptiles such as the crocodilians and sea creatures such as the sea urchin. For the most part, the animals that are alive today have made evolutionary changes from the forms they had when dinosaurs were alive. For example, though the event that caused dinosaurs to die out also killed many other reptile species, several surviving reptile species have direct ancestors from that era, including the crocodilians, which are smaller than their Mesozoic ancestors.Full Answer >
The earliest conclusive evidence of the evolution of dinosaurs dates their origins to 230 million years ago. They are believed to have evolved from other reptilian species and developed certain defining characteristics, such as specialized hip and leg bones.Full Answer >