Dinosaur egg clutches not as simple as chicken eggs

Hannah Susorney and Christi Lorang investigate dinosaur eggs at the Zhejiang Museum of Natural History in China. (Photo by Josette Wooden Legs).

Our group is looking at clutch patterns in dinosaur eggs at the Zhejiang Museum of Natural History. This data includes egg spacing, egg size, egg orientation within the clutch, and sedimentology within the eggs and the surrounding rock. Observation of egg clutches allows for greater interpretation of dinosaur reproductive behaviors and the depositional paleoenvironment of the clutch than looking at the individual eggs alone. The observations of dinosaur clutches can be compared and contrasted with the nesting behaviors of their modern relatives: turtles, lizards, crocodiles, and birds.

So far we have looked at more than a dozen clutches of eggs. We consider the clutches to be incomplete since the eggs are found on blocks dug out of the hillside, and there are usually parts of eggs missing along the edges of the rock. For many of these clutches it is impossible to tell if they would have continued beyond these edges. The eggs within the clutches we are looking at are mostly round to slightly oval. The eggs are usually 6-9 cm in diameter. Sometimes in the clutches the eggs overlap or touch each other and sometimes they are spaced with around 2-6 cm separating the eggs.

Frankie Jackson, left, and Christi Lorang investigate one of the environments that yielded dinosaur eggs in China. Some of the eggs were found on blocks dug out of the hillsides. (Photo by Josette Wooden Legs).

One major difficulty with collecting data for interpretation is the lack of information concerning the location and orientation of a clutch within the overall sedimentary structure at the site of discovery. This is because farmers and construction workers often discover the eggs which are then given or sold to museums. The information about their arrangement within the rest of the outcrop is often unknown. Thus which side of the clutch represents the original top and bottom is often unknown and we have to search for sedimentary features in the remaining sediment for clues.

Another issue we have discussed is whether the eggs are oriented in the original pattern, or if hydrologic and geologic forces have changed the orientation of eggs or even re-deposited the eggs in a new environment due to fluvial action.

Hannah Susorney and Christi Lorang look for clues regarding the history of dinosaur eggs in China. (Photo by Josette Wooden Legs).

When we return to Montana we hope to continue our research on the egg clutches. Thin sections will allow us to look at the porosity and microstructure of the eggshell. We are interested to see if there is a correlation between porosity size and spacing of the eggs within the clutch, because this could further our interpretation of nesting behavior of dinosaurs. — Hannah Susorney and Christi Lorang

Hannah Lorang, posing next to Buddha, is one of nine Montana college students seeking answers about dinosaur eggs in China this year. (Photo by Josette Wooden Legs).

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