DMNS paleontologists start actual excavation of the Cretaceous turtle by determining the extent of the fossil.

DMNS staff, aided by volunteers who have completed the DMNS Certification in Paleontology Program, often start by taking photos and/or sketching the fossil and recording its orientation with a compass. Also crucial is recording the fossil's exact latitude/longitude on a map, and its locality number, a unique ID assigned to that locality. They might even complete a measured section (see Measured Section techniques in Follow a Plant for more information).

Latitude/longitude coordinates and the fossil's position in a vertical column of sediment enable paleontologists and geologists to better determine the fossil's exact age. Recording how the fossil bones are arranged may help in figuring out how the animal died and what happened to its remains afterwards. Once the digging starts, this information is gone, so paleontologists have only one chance to record it accurately.

Happy paleontologists surround the pedestaled turtle.

Paleontologists try to determine the extent of the fossil since only part of it is likely to be exposed when it's found. Familiarity with the fossil animal helps in the process, as do careful excavation techniques. When the fossil is delicate or its exact size and shape aren't known, DMNS paleontologists frequently use small tools like toothbrushes to remove sediment. (There are exceptions. Sometimes, when the fossil's size and shape are well known and the sediment is rock hard, they might actually resort to jackhammers, but don't try this at home.) Working very carefully, they dig around the fossil's edges to form a pedestal. Next, they jacket the fossil's top surface.

Jacketed top side of turtle

Paleontologists use jackets to protect the fossil, both from the jostles and bumps in the ride back to the Museum, and from environmental conditions that might damage it. Jacketing a fossil means wrapping it a bit like you would wrap a broken bone. To cushion the fossil from the jacket, DMNS paleontologists might use a layer of loose dirt or paper towels. The jacket itself is comprised of strips of strong material (usually burlap) and plaster that is mixed on site. Good coordination and teamwork are important in this process since the group needs to securely jacket the fossil before the plaster dries.

Preparing to jacket the underside of the turtle carapace

Once the top surface of the fossil is jacketed, DMNS staff and volunteers give the plaster time to dry. Next they detach the fossil from the underlying sediment, often with pickaxes, flip the fossil, and jacket the other side. How much excess sediment is included in the jacket? There are no hard and fast rules. More sediment may mean more protection for the fossil, but it also makes for a heavier jacket.

Tradition

Common sense

Fossil vertebrates have two characteristics you don't like to see together: they're heavy and fragile. And they can be absolutely huge. In 1992, DMNS preparator Bryan Small found a stegosaur fossil near Cañon City, Colorado. It turned out to be one of the most complete stegosaur fossils ever found. It also proved too heavy for anyone to pick up. Getting it out of the ground was sort of a civil engineering feat. Volunteers with mining equipment tunneled under the fossil and inserted wood beams the size of railroad ties for support. Next, DMNS volunteers jacketed the fossil from underneath. After the plaster set, the stegosaur was airlifted by an Army helicopter. Courtesy airlifts by Army helicopters are relatively rare, however, and jacketed fossils usually have to be carried by hand. Some of the most heroic moments in paleontology come when it's time to carry the vertebrate fossil to the truck!