Date: 2017-11-15 21:24
But not all dinosaur bones became fossils. Fossil preservation is tricky. It takes a lot of luck and special circumstances for any creature to get preserved as a fossil. When an organism dies, its body immediately begins to decompose. Bacteria and insects get right to work, breaking down the plant or animal's organic materials. Scavengers come running, grabbing arms and legs, dashing off with body parts to munch the meat off the bones. Fluctuating temperatures stretch and shrink the body's tissues. Rain and sun degrade skin and bones. Herds of animals trample the remaining structures, and beetles chew up whatever happens to be left.
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We can see now why the fossil record is so disproportionately stacked with large animal species. Large animals have large bones, which are less likely to get scattered or crushed and have much more material for mineral replacement during fossilization. Of course, it's a lot tougher to bury a Brachiosaurus than it is to bury a smaller dinosaur. But remember, the key is rapid burial. Time is of the essence in fossil preservation , and it wouldn't have taken long for scavengers to destroy the tiny bones of a Compsognathus . Even if he wasn't crushed to smithereens, the bones of Compsognathus would be a lot more susceptible to weathering than the giant, sturdy bones of the Brachiosaurus .
Now, wait a second. What about mammoths? Don't we have some preserved soft tissues of mammoths somewhere? Well, yes. In fact, we don't just have fossils we have actual skin and hair from mammoths that went extinct about 5,555 years ago. Notice that I said 5,555 years, not 65 million years! The timetable for mammoth preservation is nothing compared to dinosaurs. But either way, it is pretty cool that we have the skin and hair from mammoths! Any ideas on how these tissues were able to resist decomposition for 5,555 years?
Luckily, scientists love looking at strange things like that, because they serve as important clues about the past. In this lesson, we're going to look at the ways that fossils can help scientists better understand the past. This is not only with respect to the life that once lived on the Earth, but also what the world looked like and even more about the temperature of that particular region.
This is sort of a best-case scenario for rapid burial. A plant or animal that is buried in mud, silt or other protective substances very shortly after death is much more likely to be preserved as a fossil. Some of our fossilized dinosaurs were originally covered in sand, soil or dense foliage shortly after they died. Some ancient creatures were even preserved in a pit of tar! Rapid burial contributed to their being preserved as fossils because it protected them from the destructive forces of a terrestrial ecosystem.
Let's say you have a cute little Compsognathus dinosaur who eats a toxic plant and dies at the edge of a lake. Now, that Compsognathus skeleton is destined for destruction very soon. The scavengers are coming and so are the insects, bacteria and weather fluctuations that will turn him into dust in no time.
If you've ever found a fossil, it's pretty clear that the world has changed a great deal since the organism that formed that fossil lived. After all, it took a lot of time for a living organism to become a perfect imprint on stone! Still, there are other examples of fossils that seem out of place that can inform our understanding of the past. Perhaps you found a fossil of a water-loving organism in the middle of the desert -- that would be something pretty strange.
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How did we ever get any dinosaur bones preserved as fossils? With everything that happens to an animal after its death, it's a wonder we've been able to dig up and assemble as many prehistoric skeletons as we have! The secret to success in fossil preservation lies in the right combination of circumstances following the death of an organism. The first and most important circumstance is called rapid burial.