From the Field to the Institution

Chapter 2 mentioned that searching for fossils can be hard work, but it did not examine the difficulties of properly collecting fossils, especially those of dinosaurs. Fortunately, many dinosaur body fossils are either from relatively small individuals or just a few parts of larger individuals. However, finding a nearly complete specimen of a large theropod (Chapter 9) or sauropod (Chapter 10) means that the logistics

for excavating and transporting the fossil from the field site are involved and expensive. Large excavations can potentially take an entire field season (usually summer) and require the services of heavy equipment for extraction and transport of the specimen. Furthermore, after transport and deposition of the fossil to a preparator, the preparation time for extracting a dinosaur skeleton may take more than a year. Dinosaur trace fossils, especially tracks (Chapter 7), typically do not require recovery, but some are taken from the field site for further study or display; entire beds containing the tracks may have to be moved thousands of kilometers.

To describe a typical recovery procedure, assume a dinosaur fossil consists of skeletal material. Upon identification of partially exposed and recovery-worthy skeletal remains, the area immediately surrounding the fossil is carefully cleaned. This action is followed by a full assessment of the horizontal and vertical extent of the skeleton, which normally involves mapping the distribution of the bones on a grid (Chapter 3). The orientation of any bones at the surface is noted; most may be flat-lying (parallel to bedding) and predictable in their extent, but others might project outside the exposed area below the surface. Erring on the side of caution is always good, even if it means carrying out too much rock for a small amount of fossil material. Of course, the person doing the recovery uses a scientific methodology: a prediction and its accompanying evidence determine the probable extent of the skeletal material. Then that person consults with any colleagues at the site to learn their estimations to seek consensus.

Any glues needed to keep bone fragments together are then applied. But choosing which glues are used should be left to a professional, as not just any glue should be applied to a 65+ Ma fossil! Excavation then begins on the area around the fossil. In some instances, the skeletal material (especially teeth or small vertebrae) may already be loose on the ground. Such material is placed into labeled sample bags after its distribution has been noted. Whether excavation is easy or difficult depends on the surrounding rock (Fig. 4.9). If the bones are in well-cemented sandstones, jackhammers or backhoes are not unreasonable tools for breaking up the rock. Some rocks, such as a mudstone or poorly-cemented sandstone (Chapter 7), can be picked away with rock hammers, trowels, shovels, or other hand tools. The excavation should then proceed around the prescribed area and to the perceived maximum depth for the fossil (maybe a little more, to be safe). Once this depth is reached, the excavation starts to cut underneath the fossil, although not far enough so that it collapses. This procedure causes it and the surrounding rock to form a pedestal. Water-soaked paper towels or toilet paper are then placed on the pedestal to form a barrier between the fossil and the final surrounding layer. At this stage dry plaster of Paris is mixed with water for dipping strips of burlap, which are placed around the towel-enveloped pedestal as a jacket. New materials that are less dense and more cost-effective than plaster of Paris, yet not sacrificing strength, have been proposed in recent years, but many dinosaur workers still

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