Posted on June 29, 2022
This is an update of my post published on June 29, 2011:
On this day in 1994, Dr. Tom Rockwell and his student Kevin Colson found the fossilized skull and shoulder blades of a pygmy mammoth sticking out the sand and rock on Santa Rosa Island, in California.
(The word pygmy means “small,” and of course mammoth means “large,” so the pygmy mammoth's name is an oxymoron—that is, a phrase that seems to contradict itself. Of course, mammoths were creatures in the elephant family; the various now-extinct mammoth species were quite hairy compared to modern elephants because they lived during the Ice Age and at higher latitudes than the equator-hugging lands where modern elephants live. The pygmy mammoth fossils discovered on a California island represents a kind of mammoth that is smaller than other mammoths.)
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Pygmy mammoths compared in size to "regular mammoths," above, and to a full grown human, below. |
It turned out that the fossilized skeleton that Rockwell and Colson found was nearly complete. This is the only full-sized skeleton of this particular species found anywhere, and it is also the first to be dated—it's about 12,840 years old.
How do skeletons become fossils?
Most organisms rot away to nothing when they die. Very few become fossils—but so many creatures have lived in earth's loooong history, scientists have still managed to find billions of fossils, representing hundreds of thousands of different species.
Here's one way in which an organism can become fossilized:
- An animal dies and falls to the bottom of a sea or lake.
- Soft parts rot away, leaving the skeleton.
- Dirt, sand, bits of rock and shell, and other sediment falls onto the skeleton and buries it.
- As more sediment piles on, pressure increases on the lower layers, and they turn to hard rock.
- The bones dissolve by ground water, leaving holes of the same shape, which act as molds.
- Minerals crystallize inside the molds, creating fossils that are made of minerals but that have the same shape as the original bones.
- Later (as in millions of years later), the rock is uplifted and exposed by erosion. The fossils are now exposed, waiting to be discovered.
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Of course, some fossils are not mineralized bones (above)... but rather impressions of shells or bones or even leaves or footprints (below)... |
For a longer description of the process of fossilization, go here.
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