Ya Dig?

The more I learned about the North Carolina Museum of Natural Sciences' discovery of the mystery dinosaur in Utah, the more amazed I became that the fossils were discovered at all.

That’s because while it is easy to find the full femur bone of a creature that lived 98 million years ago, it’s not that simple to spot a piece of a bone laying on the rocky ground.

Dinosaur fossils are often discovered when a piece of the bone is sticking out from the layer of sedimentary rock it is buried in. Fossils are usually found in sedimentary rocks (rocks made of sediment deposited in layers). Those rock layers were formed, or settled, at different times in history. So, to figure out where to hunt for dinosaur fossils, paleontologists need to find sedimentary rocks that formed at the time of the dinosaur fossils they are looking for. Conversely, the layer of rock in which the fossils are discovered gives an approximate time in which the creature lived.

The challenge for scientists is that the fossils they are hunting for often look much like the rocks they're buried in. In fact, set the broken piece of a fossil on a table next to a similar sized piece of sedimentary rock, and you will find it is not that easy to tell them apart.

Paleontologists at the North Carolina Museum of Natural Sciences tell me that shape, texture and color are the primary ways to identify a fossil. Here’s why.

  • Shape: Paleontologists are also experts in anatomy and biology. That’s important because they are familiar with the shapes of bones. So, even if a bone is eroded or broken, a paleontologist can often spot the distinctive shape of a bone if it is sticking out of the dirt.

  • Texture: Fossils can have a lot of different textures. Some are very smooth and shiny when compared to adjacent rocks. There are other fossils that have tiny holes all over them and still others that are striated, or lined. The key to spotting a fossil is to notice how its texture stands out from the rocks around it.

  • Color: Here’s where it gets tricky because fossils can be found in a variety of colors. Sometimes fossils stand out because of their color, but many times, a fossil can take on the color of the rock in which it was buried.

Once the fossil is found, it will be carefully excavated and packed in a plaster cast to be brought to a museum for study. But there is still plenty to learn during the dig.

Taphonomy is the study of how a fossil was buried. It comes from Greek; in Greek “taph” means burial, while “onomy” means to study. So, to learn more about what happened to an animal from the time is was buried until the time is was discovered, scientists collect data about the arrangement of the fossil in the ground, the layering of the soil around the fossil and the position of any other adjacent fossils. 

For example, finding many different fossils in the same area could indicate the area was possibly a swamp or a tar pit that trapped many animals. Finding multiple teeth embedded in bone or close by a fossil may indicate a carnivore was feeding on the dead dinosaur.

Then comes the study in the lab. But that is for another discussion another day!

- Frank Graff

Frank Graff is a producer/reporter with UNC-TV, focusing on North Carolina Science Now, a weekly science series that airs Wednesdays, beginning in August 2013, as part of North Carolina Now on UNC-TV. In addition to producing these special segments, Frank will provide additional information related to his stories through this North Carolina Science Now Reporter's Blog!

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