Humans that were assumed to guard over the wildlife creatures, leads to the extinction of most, if not all, animals.
Dinosaur Extinction Dinosaurs inhabited the earth for over million years, during the Mesozoic Era. Most dinosaur species lived and died out during this period, but at the end of the Cretaceous period 65 million years agoall remaining types of dinosaurs with the exception of birds which had already evolved, and are widely believed to be descended from dinosaurs died out.
At the same time many other Extinct smilodon for example Ammonitesand Belemnitesas well as Pterosaursand many large marine reptiles such as Mosasaurs. Plesiosaurs and Pliosaurs also became extinct.
In fact, all animals weighing more than 55 pounds 25 kilograms seem to have died out! While are not sure what happened, we do know that something happened at about 65 million years ago.
This event shows up as clear boundary in the rocks, known as the "K-T boundary", the extinction event usually being referrred to as the "Cretaceous-Tertiary mass extinction".
Smilodon The extinct saber-toothed cat (Smilodon fatalis) is probably the most well-known species at Rancho La Brea, as well as being the California state initiativeblog.com saber-toothed cat fossils show evidence of healed injuries and diseases that would have otherwise crippled the animal. This suggests that they may have been social animals; living in groups that included old and infirm individuals. Smilodon. Smilodon was the largest saber-toothed cat (or saber-toothed tiger). It was a fierce predator about feet ( m) long and 3 feet ( m) tall. The dire wolf (Canis dirus, "fearsome dog") is an extinct species of the genus initiativeblog.com is one of the most famous prehistoric carnivores in North America, along with its extinct competitor, the sabre-toothed cat Smilodon initiativeblog.com dire wolf lived in the Americas during the Late Pleistocene and Early Holocene epochs (,–9, years ago). The species was named in , four years after.
Scientists have proposed many different possible Extinct smilodon for what may have happened, and why this mass extinction might have happened: Sometimes these suggested explanations are informally called "theories", however in this case "hypotheses" is the correct term, since in science a theory means a well-substantiated explanation of some natural phenomenon or observation, whereas as "hypothesis" means a suggested explanation which needs to be tested against experimental evidence.
Asteriod Impact Hypothesis Hypothesis: An asteriod hit the earth. Apart from the immediate impact of fires and flooding if it hit the seathis would have caused catastrophic changes in the environment because of the dust thrown up in to the air blocking out sunlight.
This is currently the most popular hypothesis with scientists, because, as Luis and Walter Alvarez pointed out, iridium which comes from asteroids has been found all over the world in rocks at the K-T boundary which were laid down at the time of the mass extinction.
There is also a large crater at Chixulub in southern Mexicowhich appears to be of the right age, and could have been made as a result of an asteroid hitting the earth. Volcanoes there is known to have been very active volcanic around this time, especially in India in a region that is today known as the Deccan Traps could have caused catastrophic changes in the environment.
The dust from volcanoes would have affected the climate, sulphur from volcanoes could have caused immensely strong acid rain, and poisonous substances such as selenium could have been released into the atmosphere.
After the Asteroid Impact Hypothesis, this is probably the second most popular explanation among scientists - partly, because we know that volcanoes were active at about this time.
A nearby star exploded as a supernova. A nearby supernova would have bathed the earth in deadly radiation. If this hypothesis is true, rocks at the K-T boundary should contain Pu a long-lived isotope of Plutonium.
However, this does not seem to be the case. Climatic Change Hypothesis Hypothesis: Depends on the particular climate change theory in question.
This hypothesis can not be discounted, and even if climate change was not the main cause of the extinction, it could have played a part - there is some evidence that the Earth cooled at the end of the Cretaceous period.Information about the Sabre-toothed cat Smilodon and other prehistoric creatures.
Milestones of Paleontology related Philatelic items. List of the first: stamp, FDC, postal stationery etc. depicted prehistoric animals, dinosaurs, paleontologists.
"Smilodon is a comprehensive treasure trove of new studies and revelations about this enigmatic cat. Werdelin, McDonald, and Shaw provide fertile ground for the emergence of new research and insights into a unique predator that is now extinct!".
Dinosaur Extinction Dinosaurs inhabited the earth for over million years, during the Mesozoic Era. Most dinosaur species lived and died out during this period, but at the end of the Cretaceous period (65 million years ago), all remaining types of dinosaurs (with the exception of birds which had already evolved, and are widely believed to be descended from dinosaurs) died out.
Information about the Sabre-toothed cat Smilodon and other prehistoric creatures. Roman Uchytel is a paleo-artist and graphic designer who works from fossil skeletons of these creatures from the Paleocene to the Holocene and uses his knowledge of biology and animal anatomy to bring to life extinct predators, herbivores and omnivores, placing them in their natural environment.