Four-year-old Wylie stretched his little legs as far as they would go as he hurried to keep up with
his father’s longer stride. They zig-zagged and backtracked down the hill, both closely observing
the dirt-covered ground in their path. This was not the first time they had traveled to places
like this one; dry, rocky...and full of potential discoveries. They often spent their free time
looking for fossils. Wylie loved to explore with his dad, dig in the dirt, and pick up heavy rocks.
At a construction site in Texas, Wylie skipped ahead of his dad when he saw something
half-buried in the soft dirt. Excitedly, he picked up the bone and rushed it back to his dad.
His dad examined the bone closely; at first glance he thought it might be from a turtle, but
something about it just seemed special. He showed it to paleontologists at a local university and
his suspicion was confirmed. It wasn’t a turtle bone--in fact, Wylie had discovered a dinosaur
bone! Scientists believed the fossil could belong to a nodosaur, an armored plant-eating dinosaur.
Some fossils are discovered by accident, by regular people going about their everyday
lives. But most are found by paleontologists who have methods of finding specimens.
They use a process called prospecting, which is looking for fossils in areas
where they are most likely to be found. Wylie and his dad were prospecting
by searching in areas of ground recently disturbed by construction.
But how do paleontologists know where fossils are most likely to be found? One of the primary
methods is by studying geological maps of the Earth. These maps show where different types of
rocks are located. Fossils are most often located in sedimentary rocks, which are rocks formed in
layers over time, preserving skeletons inside the layers. Paleontologists use these maps, along
with knowledge of how and where specific species lived, to narrow their search to likely places.
Once they choose a location, paleontologists start to dig through layers of dirt and rock,
looking for fossils, which can be a difficult process. Paleontologists are trained to look for
variations in the rock and dirt layers. They try to find differences in the rock’s shape, color,
size, and texture, any of which might indicate a fossil. Amazingly, if they
find something they think may be a fossil, paleontologists can test it by licking it!
Because bones are full of tiny holes or pores like a sponge, when you lick a fossil
it will suction to your tongue! Would you want to lick this fossil?
Once a fossil has been located, paleontologists will carefully clear away the top layer of
dirt from it, and the surrounding area, to see if there are any other fossils nearby.
They will section off the dig area and create a map of the site
and the fossils within. Like a detective writing down clues, paleontologists have
to take detailed notes of the site. They make observations on where the fossils are found,
how close they are to other fossils, and what the rock is like surrounding the fossils.
All of these clues will give them information about the dinosaur they have just found.
After finding a fossil and mapping its location, they are ready to begin digging, or excavating.
They will start by digging a trench around the fossil. Paleontologists use special tools in
their work, and as a general rule, the closer they work to the fossil, the smaller tools
they use. To begin excavating the trench they might use shovels, pickaxes, or jackhammers.
Then, as more of the fossil is revealed they switch to smaller tools like chisels,
hammers, brushes, and eventually even tooth brushes or dental picks! Fossils are extremely
fragile and paleontologists have to be careful as they work to remove them. It might surprise you to
learn that fossils are not fully excavated at the site. They remove as much of the surrounding rock,
or matrix, as they can safely and then begin the next step of the process.
Once the fossil, with its surrounding layer of rock, has been removed from the ground,
it is covered in a thin layer of toilet paper. That’s right, the paleontologists
wrap the specimen in toilet paper to prepare it for the next step,
which is called jacketing. This step can get a little messy. Special pieces of cloth are dipped
in plaster of paris and then draped over the toilet paper and around the top of the rock.
As this mixture dries, it creates a hard surface, a safe little jacket, around the fossil.
When the top is dry the entire thing has to be carefully flipped over
so the other side can get the same treatment. This is quite easy if the excavated piece is small,
but some fossils are not small! For example, paleontologists excavated a chunk of rock in Utah
that weighed over 18,000 pounds. It was so big it was referred to as the Utahraptor Megablock.
Flipping this massive piece over required a little extra help from some heavy machinery.
Why does the rock need to be covered in a plaster jacket?
This protects the fragile fossils as they are transported back to the lab,
where paleontologists will continue to work on extracting them.
Transporting the fossils can be quite difficult as they are generally found deep in rocky landscapes,
far from any trail or road. Paleontologists have to get creative in how to move these heavy
plastered chunks, carrying them out by hand, by carts, or by off-road vehicles. In the case of
the Utahraptor megablock, a road had to be built up the side of a mountain to reach the site.
Once the specimens have safely arrived at the lab, paleontologists work to separate the fossil
from the rock, or matrix, surrounding it. They first remove the hard plaster jackets, which are
so strong they require a saw. Next, they need to remove the surrounding rock. To accomplish this,
they often use an air scribe tool. These look like a pen or stylus and can blow small bursts
of compressed air thousands of times per minute to help break down the rock. This is a meticulous and
slow process, often taking months to complete. Once the rock is removed, paleontologists work
to piece together many small fossil fragments to recreate the bones they came from.
This is tricky since the pieces are often tiny and might even have parts missing! Dinosaur fossil
skeletons, like this one, are complicated jigsaw puzzles that can take years to put together!
Excavation of fossils can be a painstakingly slow and difficult process for those who devote
their lives to it, but the challenges are outweighed by the joy of discovery.