The Gobi Desert - page 4
Screenwashing
Dinosaurs are hard to miss: their whopping bones don't slip easily from one's hands. But most fossils are tiny and difficult to notice in the soil. That's why researchers practice "screenwashing": they sieve the collected material with water, and once the residue has dried in the sun, they can pick out the fossils!
How can we determine the age of fossils?
The age of fossils is rarely estimated by sophisticated and expensive techniques such as carbon dating. But we know that a fossil is as old as the layer in which it is found!
For that reason our researchers collect microfossils as well: calcareous skeletons of micro-organisms, preserved for millions of years. For instance, the reproductive organs of some freshwater plants, like the Charophyta algae (see figure), have a calcareous shell. Once fossilized, it can tell the age of a layer and the other fossils within!
Back in Belgium
At their arrival in Belgium the fossils will be meticulously sorted according to type (different bones, teeth, cranes...), size and shape. Then begins the tough work: all collected fossils have to be compared with photographs in scientific journals and with other fossils of our own and our fellow palaeontologists' collections.
Most early mammals were very small, and their fossils are mainly teeth, since teeth preserve best. Imagine the size of a tooth or a phalanx of an animal of 5 cm length. It's no wonder that a microscope is very useful here, and they have electron microscope photographs made of the most interesting fossils, in order to see their slightest details.
