The eyes, dead and turned to stone, were even now regarding him. It was one of the early crustaceans called Trilobites. With more than 15, recorded species, trilobites were a fantastically diverse group of arthropods that roamed the oceans from about million to million years ago. Arthropods are characterized by pairs of jointed legs and a segmented exoskeleton. Today, they account for more than 80 percent of animal species and include insects, spiders, crabs and their many relatives.
About a century after Hardy penned his novel, I sat at an exposure of shale along the edge of a dark wood in Germany. I was a high school student traveling with fellow collectors and looking for fossils from the Devonian Period, million years to million years ago. I kept splitting blocks of shale to look for fossils buried within them. With a slight tap of my rock hammer, a piece of rock parted to reveal the head shield of a trilobite.
The fossil stared back at me with its sightless eyes while I marveled at the fact that I was the very first human to see it after it had spent some million years in the ground. The imperiled Mr. Knight accidentally came face to face with a trilobite. By contrast, I did so after studying geological maps. I knew the age of the shale and I had a pretty good idea of the kinds of extinct animals I might find. The two stories nicely illustrate the two most common ways of finding fossils.
Collecting does not require formal training. Indeed, some of the finest collectors I have hunted fossils with include a policeman and a veterinarian. The fantastic shapes of certain fossils make them objects of aesthetic pleasure to other collectors. Many fossils are discovered by sheer accident. Paleontologists will determine the most likely location of fossils using as much information as possible, including paleogeography and biogeography data, as we mentioned in the intro.
Paleogeography is studying geographics to determine what the land may have looked like in days long since passed, like the Jurassic Period or Cretaceous Period. Paleogeography involves assessing current day vegetation, soil, climate, and topography and then comparing it to how it might have been millions of years ago to indicate where fossils may be. Geologists may also help in fossil hunting. They may look for metamorphic fossils and those trapped in volcanic sediment, but fossils sites are less likely to appear in these areas.
Even compared to lake sediments, river sediments tend to yield fewer fossils. After determining where on the map could have the most fossils, the paleontologists will comb the area, looking for sediment changes to gauge whether a fossil may be there. Then the paleontologists will dig.
Although it sounds so, unearthing fossils is not an exact science by far. A good paleontologist will admit that luck plays a role in whether the piece of rock contains any fossils or if the uncovered fossil is expected. Excavations take different shapes and forms.
They can be a one or two scientist team following a hunch. Alternatively, they can be bigger teams. Geologists, biologists, paleontologists, and students can team together to excavate an area that they believe hold fossil specimens. Often, before the dig begins, the scientists scour over geological maps, fossil history, and previous fossil collecting expeditions in the same area to give the possibilities of finding their potential fossil discoveries.
It can take days or weeks to assemble the team to the fossil bed area and additional weeks to properly excavate the place.
That said, some areas worldwide are renowned for containing more fossils than average. You could say that paleontologists are looking for fossil evidence within the layers of rock they are thinking of digging.
Through his research and many other paleontologists, the world got such fossils as the Allosaurus, Diplodocus, Apatosaurus, and Stegosaurus.
Over on the east side, the Cretaceous Dakota Formation had lots of footprints that may belong to dinosaurs, hundreds of these prints in all. The prints may have come from the Eolambia or Iguanodon, maybe even both. Petrified Forest National Park is another great place to find fossils. This Arizonian land in Apache and Navajo counties is named not for petrified fossils but rather, wood.
The difference really depends on the type of rocks it's embedded in. Scientists have trialled methods such as ground-penetrating radar to locate bones underground.
But so far they haven't been effective enough, which suggests that for now the traditional approach to dinosaur hunting works best. Once you've selected a spot where there may be bones below the surface, getting a dinosaur out of the ground often requires a lot of digging.
Mark Graham , a fossil preparator at the Museum, works to excavate fossils from the Morrison Formation. In places where there is a lot of overburden the rocks overlying the material you're trying to dig up , palaeontologists may use heavy machinery to remove it and gain access to the fossils below. Early fossil hunters sometimes resorted to dynamite to blast the rocks apart to get to the bones. Once closer to the bone bed, palaeontologists switch to smaller tools such as trowels, brushes and utility knives.
It can take days or even weeks of painstakingly working around a bone to be able to remove it from the ground with minimal damage.
Dinosaur bones can be very fragile. Even those that appear large and heavy can't always support their own weight when lifted out of the ground, as they may have fractures running through them. Even the largest dinosaur bones can be fragile and fracture. These sauropod bones were found in the Sahara Desert in the s.
Fossils can break during the excavation process. Paul says, 'It's actually quite common. When you're taking a bone out of the ground, you aren't exactly sure where the ends of it are or where it starts going into the ground. We just keep the little pieces and they get stuck back on. We take really good care of them. We're very good with glue and we can usually make the bones right again.
To protect the bones during transport, palaeontologists use field jackets. This involves using plaster of Paris and burlap to create a cast around a bone, similar to the casts doctors use to stabilise a broken arm or leg. A sauropod bone in the Sahara Desert is wrapped in plaster and burlap in a process known as jacketing. In the lab, a fossil preparator will remove the plaster jacket, then the rocks surrounding the bone, and will fix any fractures to stabilise the bone.
Fossilised dinosaur bones aren't always the only things found during an excavation. Other scientifically valuable information and specimens can be uncovered, such as evidence of early mammals and invertebrates, as well as trace fossils such as coprolites or trackways.
Usually a dig isn't just spent getting the dinosaurs out of the ground. Scientists will also take the time to study the rocks and excavate other fossils they find along the way.
On the Mission Jurassic excavation, scientific associate and microvertebrate expert David Ward led a team to engineer a sieving machine in the field, which was affectionately known as Hank.
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