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 mammoth means “large,” so the pygmy mammoth's name is an oxymoron—that is, a phrase that seems to contradict itself. Of course, mammoths are creatures in the elephant family that were quite hairy compared to modern elephants, and that are now extinct. Pygmy mammoths are mammoths that happen to be smaller than other mammoths.)
It turned out that the fossilized skeleton of the pygmy mammoth 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 made of minerals but in 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.
For a longer description of this process, go here.