What do you think wiped out the dinosaurs? Or are they still with us?

Dinosaurs

The Dinosaurs were all wiped out a long time ago, as everyone knows (or do they? Maybe they are still with us in the form of birds). The dinosaurs are thought to have died out during the late Cretaceous period, having lived from between 280 and 65 Ma ago. Human beings, by comparison, arrived on the scene about 1 Ma ago. There were very few mammals during the time of the dinosaurs.

Over the years there have been several theories why dinosaurs died out; some fit the evidence better than others. The best known one is that a large meteorite struck the Earth on the north coast of the Yucatan Peninsula in Mexico, and that so much dust was kicked up into the atmosphere that little sunlight could get through. There would have been earthquakes and fires and rain acid enough to harm the skin of amphibians and the fresh water. The plants that many dinosaurs depended on (we can often tell from their teeth what kinds of food they ate) might well have died for lack of light. A similar theory suggests that a major volcano eruption had similar effect.

Another is that there was radiation from one or more supernovae. Yet another was climate change, as the climate was cooling at the time, and finally, there's the theory that mammals and flowering plants evolved that the dinosaurs could not eat - though that seems less likely.

If the climate cooled, for whatever reason, then reptiles would have suffered first.

Dinosaurs came in many shapes and sizes, and they filled many niches, just as mammals do today. Some were meat-eaters, some ate fish and some were vegetarian. Some were hunters and some were scavengers. Some walked on 2 feet and some on 4, some lived in the seas, and others flew.

The Pterosurs could fly. They varied considerably in size. The Anurognathus had a wingspan of 50cm. Quetzalcoatlus, on the other hand, had a wingspan of 13 metres.

It is not yet clear whether modern birds evolved from dinosaurs or from thecodonts such as Phytosaurs which were 2 metres long and closely related to the crocodiles.

As can be seen from recent news stories we are still learning about dinosaurs, and what we learn may make us change our minds about whether any of their relatives still survive and how they became extinct.

Dinosaurs had respiratory system like birds -study, Were Dinosaurs More Like Birds ?

The respiratory system of dinosaurs appears to have been much more similar to that of birds, rather than to that of crocodiles as had previously been thought.

Recent news stories involving dinosaurs include:

• Dinosaur Track Found in Alaskan Park July 06 2005
• Scientists Study How to Tell T. Rex's Sex June 03 2005
• "Ancient Fossils, New Discoveries" June 03 2005
• Researchers Find Sauropod Dinosaur Skulls June 02 2005
• Short-necked dinosaur challenges accepted theory June 01 2005
• Paleontologist Helped Film With Delay May 12 2005
• Dinosaur Exhibit Opens at NYC Museum May 11 2005
• Dinosaur Found That Turned Vegetarian May 09 2005
• Paleontological Art Available on Internet May 07 2005
• Newfound Dinosaur Shows Transition in Diet May 05 2005
• Dinosaur 'missing link' unearthed in Utah May 05 2005
• Newfound Dinosaur a Transitional Creature May 04 2005
• South Dakota fossil yields new dinosaur species May 02 2005
• Scientists Find T.rex Relative in Georgia April 15 2005
• Dinosaur Eggs Offer Clues on Reproduction April 14 2005
• Dinosaur Fossil Carries Bird-Like Eggs Inside April 14 2005

Please see the following message for the remaining stories.

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What do you think wiped out the dinosaurs? Or are they still with us?

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