Fossiling

The posted photos show some scenes from the past week of fossiling in the White River badlands of Northwest Nebraska, (Sioux County). The geologic strata we were searching in covered the time period of about 34 to 30 million years before present. The lower strata captured animals that roamed the area when it was a much wetter, rainforest environment, according to Dick. Above this is a layer of white ash from distant volcanic explosions. The more recent (only " 30 million year ago sediments record a much drier time. The animals present at the various times varies.

It's amazing to consider how much one spot of earth has changed over time. Down below any of the sediments we could look at were shales from even more ancient times when a sea bed was present.

The most abundant fossils in the White River formations are tortoises and oreodonts ("oreos" for short). There are many types of tortoises, and their pieces are widely scattered about. You might find a tortoise fossil from the top shell (the carapace), the lower shell, (the plastrons), or if you are really lucky, the entire shell.
Sometimes what's preserved is not the shell at all, but the inner tissue, which
has fossilized apart from the shell. These are called "nougats." Someone even found the fossilized brain cage of a small mammal.

That's what is in the one picture of the rounded blob on the rock pedestal. It is a landmark at one site.

The second common fossil is usually some part of an oreodonts, a four-legged sheep-sized grazing animal. We found many parts of these once-common grazers, including teeth, legbones, and vertebrae.

Over the week, different members of the group also found portions of a titanothere, a gigantic vegetarian, and a subhyracadon, an extinct rhinocerous. The largest find of the week was a group of fossilized skeletons on top of each other in what may have been a den.

That was the one that had to be carried out by four people at a time.

As we went along, we learned how to spot a bit of exposed tooth or tortoise shell by scanning how the light played on the sediments. Each find was carefully extracted, jacketed with the same bandages that are used to make casts, and removed after its GPS location was noted. The casts are later prepared by talented folks who piece together disjointed parts, fashion missing parts where necessary to complete a skull.

It takes a lot of work to get a specimen from the field to the museum. Even more important, it takes a lot of study to understand why the animals were present when and where they were, how they changed over time, and how they related to one another.