The best areas for collecting fossils are where the landscape is dry and barren, with no plant cover to obscure the rocks underneath. Typically, these areas form deeply eroded, weird landscapes known as badlands (fig. 6.1A–B). Badlands get their names because they are a bad place to lose a cow, or to try to cross if you don’t have lots of water—but to a fossil collector, badlands are good lands. In fact, most of the best fossil collecting is found in areas that were given diabolical or hellish nicknames, such as “Devil’s Punchbowl” and “Hell’s Half Acre.” They may have looked barren and forbidding to early settlers who were seeking flat grassy soils, but they are heavenly for fossil collectors.
Figure 6.1 ▲
Two fossiliferous badlands exposures: (A) Oligocene rocks in Badlands National Park, South Dakota; (B) Miocene rocks in Redrock Canyon State Park, California, a filming location that claimed to be Cretaceous beds from “Snakewater, Montana” in the first Jurassic Park movie. (Photographs by the author)
The badlands are good lands to look for fossils that are extremely rare. Fossils of dinosaurs and prehistoric mammals and most backboned animals rarely occur in large concentrations such as shell beds or leaf beds. You need to do a lot of prospecting: walking along the exposed area slowly, eyes to the ground, looking for any telltale color or texture that tells you that you are looking at fossil bones or fossil teeth. Fossil bone, for example, can usually be recognized by its spongy texture on the inside and a solid outer core of bone, and often by a shape that corresponds to a known bone shape. For this reason, a good paleontologist is an expert in recognizing almost any bone of any kind of animal found in the fossil beds where the search takes place. Fossil teeth, which are the most durable and diagnostic parts of any mammal skeleton, are usually spotted by the shiny glint of enamel on their outer surface.
Most often, these fossils are collected after hundreds of hours walking slowly in the hot sun, trying to see the bones or teeth on the ground amidst all the other colored pebbles and other rocks that distract you from what you are seeking. Often you spot something that looks promising, only to pick it up and find it’s just another pebble, or a concretion that looks like a fossil. In places where dinosaur or mammal fossils are found, the terrain can be very remote and rocky and even dangerous. Typically, badlands are steep and rocky. You must be prepared for hardcore hiking: good boots, comfortable durable clothes suitable for the weather, a broad-brimmed hat to keep the sun off and lots of sunscreen, and plenty of water and snacks in your pack, especially if you are out collecting all day in the heat and glare of the sun.
Once you spot a promising object sticking out of the ground, you might investigate it further to see if it’s a fossil or not. Even if it does turn out to be bone, it might be too fragmentary or incomplete to be identified. If it’s a worthwhile find, you may need a brush to clean it off, a rock hammer or an awl to pry it from the rock, or a chisel or pry bar to split open the rock to see inside (fig. 6.2). In addition, to collect certain kinds of fossils, it’s wise to have a bag to put the fossil in (preferably a plastic bag with a ziplock top) and a felt-tipped pen or marker to label the bag. If the specimens tend to be fragile, you might also carry a roll of toilet paper to wrap the specimens in before bagging them up. To a paleontologist, toilet paper has many uses!
Figure 6.2 ▲
Collecting the giant fossil fish Xiphactinus from the Cretaceous chalk beds of western Kansas. (Photograph by the author)
In addition, if the fossil is bone that has a tendency to shatter or break when exposed, most paleontologists carry a small plastic squirt bottle with a preservative or hardener. The early fossil collectors used substances like shellac, but most modern paleontologists use organic hardeners such as Glyptal and Alvar, which are much easier to clean off the specimen in the lab. Once the fossil is exposed, they squirt the hardener on the specimen and let it soak in and dry, gluing the fossil together in the field and making it less likely to break.
If the specimen is large and fragile, however, a much bigger effort is required. Serious paleontologists working on larger fossils usually carry some sort of material to make a plaster and burlap jacket around the fossil, similar to the plaster cast that a doctor puts on a broken arm. When a large fragile bone is found, the first job is to carefully uncover and partially clean the specimen until you find out how far back into the rock it goes. Once you have exposed its top surface completely, you dig a trench around it and dig away all the encasing rock until the fossil is sitting with a narrow pedestal of rock beneath it (fig. 6.3A). All through this operation, the exposed parts of the fossil are squirted with hardeners to prevent it from shattering.
Figure 6.3 ▲
Large fragile fossils may need a plaster jacket to protect them before they are transported. (A) This brontothere jaw and skull were originally spotted when only a tiny corner of the jaw was seen sticking out of the ground. The paleontologists then exposed the fossils until they were on a thin pedestal of sediment. (B) After exposing the fossils, a cast made of burlap soaked in plaster of paris was applied to the exposed bone to create a hard jacket to protect the fossil. (C) Once the plaster has dried, the paleontologist uses a pick to cut down the pedestal further, then pries it loose from the ground and flips it over, exposing the rest of the fossil. A plaster cast is then placed over the rest of the specimen to protect it during transport. (Photographs by the author)
When the large fossil is completely isolated on a pedestal of rock, typically you cover all the freshly exposed surfaces with a layer of wet toilet paper to protect it from the plaster. Then you mix up the plaster of paris in a small tub or bowl according to the package directions. Meanwhile, you cut burlap sacks into narrow strips. Each strip is then dipped into the plaster until it is saturated, then it is wrapped around all of the exposed surfaces of the specimen that are covered with wet toilet paper (fig. 6.3B). The specimen is plastered across the top and around the sides and along the exposed base. After a few hours, the plaster jacket will have dried enough that you can do the trickiest part of the process. Using pickaxes and shovels, the crew undermines the pedestal as far as they dare, then uses a pick or a long piece of wood as a lever to break the fossil off its pedestal and turn it over (fig. 6.3C). If the fossil doesn’t shatter in the process (a tragedy that happens too often, even with the most careful preparations), then the exposed base of the fossil can be trimmed of excess rock. At this point, the plaster jacket can be completed over the exposed area, so the specimen is entirely encased in a hard plaster cast. Once all the plaster has dried, it can be carried out or loaded into whatever vehicle (a truck, or sometimes even a helicopter) is available and transported to a laboratory where it can be carefully cut out of the jacket and prepared.
