Back at the ranch

Once the fossil dinosaur bone is out of the field and back where it can be studied, the jacket must be cut open, and the fossil prepared, or freed from the matrix. This runs from simple brushing, to scraping with dental needles, to sophisticated treatments such as acid removal

2. Notice that the term dinosaur "dig" is a misnomer. Nobody digs into sediment to find bones; bones are found because they are spotted weathering out of sedimentary rocks.

Figure 1.10. Jacketing. (a) A fossil is found sticking out of the ground; now it needs to be cleaned off so that its extent can be assessed. Exposing bone can be done with a variety of tools, from small shovels, to dental picks, to fine brushes. As the bone is exposed, it is "glued"; that is, impregnated with a fluid hardener that soaks into the fossil and then hardens. (b) The pedestal. When the surface of the bone is exposed, the rock around it is then scraped away. For small fossils, this can be quite painless; however, for large fossils, this can mean taking off the face of a small hill. Anyway, this process continues until the bone (or bones) is sitting on a pedestal, a pillar of matrix underneath the fossil. (c) Toilet paper cushion. Padding is placed around the fossil to cushion it. The most cost-effective cushions are made from wet toilet paper patted onto the fossil. It takes a lot of toilet paper: for example, a 1 m thigh bone (femur) could take upward of one roll. On the other hand, this is not a step where we should cut corners, because returning from the field with a shattered specimen, or one in which the plaster jacket is stuck firmly to the fossil bone, is not so good. (d) Plaster jacket. Jackets are made of strips of burlap cloth soaked in plaster, and then applied to the toilet-paper-covered specimen. A bowl of plaster is made up, and then pre-cut, rolled strips of burlap are soaked in it and then unrolled onto the specimen and the pedestal. (e) Turning the specimen. After the plaster jacket is hardened, the bottom of the pedestal is undercut, and the specimen is turned; that is, separated at the base of the pedestal from the surrounding rock and turned over. This is a delicate step in which the quality of the jacket is tested. (f) The top jacket. More plaster and burlap are then applied to the open (former) bottom of the jacket, now its top. At this point, the fossil is fully encased in the plaster-and-burlap jacket, and is ready for transport from the field.

Figure 1.10. Jacketing. (a) A fossil is found sticking out of the ground; now it needs to be cleaned off so that its extent can be assessed. Exposing bone can be done with a variety of tools, from small shovels, to dental picks, to fine brushes. As the bone is exposed, it is "glued"; that is, impregnated with a fluid hardener that soaks into the fossil and then hardens. (b) The pedestal. When the surface of the bone is exposed, the rock around it is then scraped away. For small fossils, this can be quite painless; however, for large fossils, this can mean taking off the face of a small hill. Anyway, this process continues until the bone (or bones) is sitting on a pedestal, a pillar of matrix underneath the fossil. (c) Toilet paper cushion. Padding is placed around the fossil to cushion it. The most cost-effective cushions are made from wet toilet paper patted onto the fossil. It takes a lot of toilet paper: for example, a 1 m thigh bone (femur) could take upward of one roll. On the other hand, this is not a step where we should cut corners, because returning from the field with a shattered specimen, or one in which the plaster jacket is stuck firmly to the fossil bone, is not so good. (d) Plaster jacket. Jackets are made of strips of burlap cloth soaked in plaster, and then applied to the toilet-paper-covered specimen. A bowl of plaster is made up, and then pre-cut, rolled strips of burlap are soaked in it and then unrolled onto the specimen and the pedestal. (e) Turning the specimen. After the plaster jacket is hardened, the bottom of the pedestal is undercut, and the specimen is turned; that is, separated at the base of the pedestal from the surrounding rock and turned over. This is a delicate step in which the quality of the jacket is tested. (f) The top jacket. More plaster and burlap are then applied to the open (former) bottom of the jacket, now its top. At this point, the fossil is fully encased in the plaster-and-burlap jacket, and is ready for transport from the field.

Figure 1.11. Scenes from a prep lab, in this case, that of the Museum of Northern Arizona in Flagstaff, USA. (a) Foreground: a large plaster jacket containing the theropod dinosaur Coelophysis. Background: sand tables for stabilizing specimen fragments (to be glued), open jackets, storage shelves, and grinding equipment. (b) The jacket shown in (a). The Coelo-physis specimen is visible in the foreground. The arms and hands are to the left; the pelvis, legs, and tail are visible to the right. (c) A dinosaur skull (Pentaceratops) laid out for study. In the background are the large bays in which specimens are stored.

Figure 1.11. Scenes from a prep lab, in this case, that of the Museum of Northern Arizona in Flagstaff, USA. (a) Foreground: a large plaster jacket containing the theropod dinosaur Coelophysis. Background: sand tables for stabilizing specimen fragments (to be glued), open jackets, storage shelves, and grinding equipment. (b) The jacket shown in (a). The Coelo-physis specimen is visible in the foreground. The arms and hands are to the left; the pelvis, legs, and tail are visible to the right. (c) A dinosaur skull (Pentaceratops) laid out for study. In the background are the large bays in which specimens are stored.

of the rock matrix. These techniques are generally carried out in a preparation laboratory (or prep lab) (Figure 1.11).

We often expect that the final result will be a free-standing display in a museum. Mounts of real fossil bone are attractive, but also time-consuming and costly, and the metal frames that support the bones can be destructive to the fossil. Moreover, mounted specimens commonly undergo damage over time; slight shifts in the mounts because of the extraordinary weights of the fossil bones, or vibrations in the buildings in which the bones are housed, or museum patrons lifting apparently "insignificant" bits all diminish the quality of mounted specimens. In addition, when the specimens are assembled and mounted, they can be hard to examine for study.

Many museums, therefore, have begun to cast the bones in fiberglass and other resins, and display the casts. Such displays are virtually indistinguishable from the originals. With their light weight, and the possibility of internal frames, they can be spectacular and dynamic (Figure 1.12). Leaving the bones disarticulated, properly curated, and available for study maximizes returns on the very substantial investments that are involved in collecting dinosaur remains. Paleontology is carried out in large part by public support, and mounted casts give the public the best value for money.

Figure 1.12. A spectacular mount of the sauropod Barosaurus and the theropod AHosaurus. This mount is made of fiberglass and epoxy resin, cast from the bones of the original specimens. A dynamic pose like this would not have been possible using the original fossil bones.

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