Using taphonomy to further understand clutch arrangement

Hannah Wilson carts off one of the many boxes of eggs that were examined. (Photo by Christian Heck).

 

 

 

 

 

 

 

 

 

 

 

 

 

Before we get started we’re going to explain to you some basic terms pertinent to our research project:

Taphonomy: Essentially, the processes that affect an organism, eggshell, etc before fossilization. A popular way of phrasing it is the processes that act from “death to discovery.”

Clutch: A grouping of eggs that typically represent a batch from the same individual (barring any nest parasitism, communal nests, etc).

Matrix: The sediment that surrounds the specimen.

Compression ridge: A ridge that generally defines the plane at which compression took place.

A spheroolithid egg shows a clear compression ridge. (Photo by Christian Heck).

So now that we powered through that short lesson, you will hopefully better comprehend our research.

A majority of the dinosaur eggs that are found in the collections of the Zhejiang Natural History Museum exhibit a similar pattern of crushing. This crushing pattern isn’t just found in clutches but also in individual eggs. The project we’ve been working on focuses on this crushing in hopes of understanding when it occurred, as well as the effects it had on clutch arrangement in a nest of dinosaur eggs.

As the research groups of past years have explained, the way specimens are obtained in China is very different than in the States. In the U.S., we generally have huge swaths of land that are dry and clear of vegetation (think badlands), whereas here in the Zhejiang Province the ground is either covered in vegetation, farmlands, or buildings. The farmlands provide little patches of ground to prospect, but farmers generally find these first. The museum then obtains fossils from farmers, construction sites, individuals without any reference to where the fossil was found. The fossil itself is important, but just as important is the locational data from where it was recovered. Without stratigraphic data to accompany it the fossil doesn’t provide much as far as research goes.

Because farmers who find the dinosaur eggs are compensated for their finds, the Zhejiang Museum of Natural History in Hangzhou has a massive collection of fossilized eggs, and many lack that necessary stratigraphic data. In our project, we are asking whether or not there is a way to theoretically connect these eggs to one another. Now, this isn’t to say that we can definitively say that all of these eggs were once in the same plane as one another. It’s more of a way of projecting that perhaps the same type of event acted upon these eggs. So we will be going through egg clutches first, measuring the angle at which the crushing plane occurs in relationship to an arbitrary horizontal (since we are comparing the angles of each egg in a clutch, the horizontal can be arbitrary as long as it is consistently used for every egg in a clutch). We are also utilizing some geologic methods to measure the angle, or dip, and the strike of the plane of compression. Using these measurements, we hope to be able to analyze the eggs in each clutch in relation to one another.

Christian Heck measures the dip of the crushing plane.

Our second pathway to our goal of understanding the effects of taphonomic crushing is mostly through individual eggs. The collections room has hundreds of individual eggs, some with that same ol’ crushing plane. So we are setting off to determine if the similar crushing force occurs across these compressed eggs by taking a ratio of the crushed side height to the non-crushed height. That means lots of measurements on lots of eggs.

There are many challenges to this project outside of keeping our sanity as we measure eggs for eight straight hours a day. Many of the individual eggs are fragmented to the point where we can’t use them or matrix covers too much of the egg, and Christian can get grouchy if he doesn’t have snacks and the perfect background music. Despite these issues, we are confident that we can obtain some great data from these methods and look forward to sharing them with you.

Hannah Wilson analyzes the data gathered from a clutch of eggs. (Photo by Christian Heck).

 

 

 

 

 

 

 

 

 

 

Blog post by Christian Heck and Hannah Wilson

Hannah Wilson and Christian Heck (Photo by Anita Moore-Nall).

 

 

 

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