Notes from the Mini Museum: Age of Dinosaurs
Fun Fact: The eggs in this illustration were made with a texture pulled from macro images of the real dinosaur eggshell fragments in Age of Dinosaurs
"I would go to museums and say can I open your dinosaur egg? Can I just drop them on the floor and look inside? And they'd say no." -Jack Horner, Paleontologist
When thinking about deep time, we often find ourselves caught up in the grand movements and nearly unfathomable expanses of millennia stretched end to end. Yet, here in this humble eggshell, we have a single moment captured for all eternity... the birth of an individual dinosaur.
Hypselosaurus Eggshell Frgaments
The egg is an incredible natural structure designed to protect and support a growing body until it is ready to come into the world. The texture, when viewed under magnification, resembles rocky hills with a network of valleys running in between. These numerous rifts serve as channels for oxygen, sustaining the fragile creature within.
Untreated dinosaur eggshells. Note that oxygenation channels are not visible! (Source: Val, García, López 2014)
As the once-fragile eggshell solidified over time into the fossils we see today, these grooves were covered with a matrix made mostly of calcium carbonate, which happens to be the core component of the eggshell itself.
Hypselosaurus Eggshell Frgaments
Preparing the Specimen
The specimen in Age of Dinosaurs is a fragment of a Hypselosaurus eggshell from the Provence region of southern France. Recent studies suggest that the sauropod may have been a "small" titanosaur, measuring perhaps 12m (40ft) in length in adulthood.
As you might expect, fossilized sauropod eggshells can be a little dirty. In preparing the eggshells for Age of Dinosaurs, we were presented with the challenge of clearing the debris that had built up, without damaging the unique surface of the shell and preserving fine details like the oxygenation channels.
Our initial experiments to clean the eggshells led to the mutual removal of debris and the erosion of the ridged surface of the fossil. We tested various solutions and tools, but the end results were abraded and lackluster shells.
To take things to the next level, we turned to the Journal of Paleontological Techniques and an article by Spanish paleontologists Sandra Val, Rubén García, and Domingo López titled "Preliminary Results on the Chemical Preparation of Dinosaur Eggshells."
Eggshells treated with acids. A) Acetic acid at 10%. The relief of the eggshell has been damaged and eroded. B) Hydrochloric acid at 15%. The surface of the eggshell has been highly eroded (arrows). C) Oxalic acid at 10%. The relief of the eggshell could be observed, but the surface was slightly altered (arrows) and the oxygenation channels could not be detected. D) Sodium hexametaphospate (NaPO3)6 at 15%. The relief of the eggshell could be observed, its surface did not seem altered and the oxygenation channels could be detected (arrows). (Source: Val, García, López)
This study details fifteen (15!) different methods for preparing dinosaur eggshells using a variety of chemical agents. Some of the mixtures here could lead to unfortunate outcomes if prepared incorrectly, so we let Mini Museum Helper Chip take the lead since he has a degree in Chemistry.
Chip and MM Intern Ellis prepare the solution and tools to bathe a batch of Dinosaur Eggshells. They are both extremely tall so we're not entirely sure how Grant got this picture!
As pictured, Chip recalibrated our experiments using solutions with different amounts of sodium dithionite.
This is a variation on the Waller Method, where a solution of sodium bicarbonate, sodium citrate, and sodium dithionite is used to treat the eggshell without acid, which allows us to clean the dirt and debris from the surface without dissolving the calcium carbonate in the shell.
Dirt sloughs off bubbling eggshells in a bath of sodium dithionite solution.
After several tests, Chip and Ellis found that a timed bath in a 10% solution of sodium dithionite cleaned the Dinosaur Egg, letting the oxygenation channels and the ridged surface stand out on this fascinating specimen!
Many classic dinosaur books credit American George Olson with the first discovery of dinosaur eggs back in 1923 during an expedition in Mongolia. While Olson's find was the first recognized egg find, the real honor goes to 19th century French Catholic Priest Father Jean-Jacques Poech. In 1859, Father Poech came across the shell fragments of what he believed to be a giant bird. As it turns out, those eggs were really from Hypselosaurus.
Chip reviewing test results under the microscope.
Hypselosaurus was first described by P.E. Matheron in 1869 based on a selection of fossilized bone fragments. Matheron initially concluded the remains came from a huge crocodilian, but in 1890 Charles Depéret proposed Hypselosaurus was actually a sauropod dinosaur. The definition of Hypselosaurus has continued to shifted over the years from a small to midsized sauropod perhaps 12m (40ft) in length to more current theories that may assign the remains to other, more firmly defined titanosaurs.
Fossil eggshells Matheron collected from the same site where he found the Hypselosaurus skeleton bits are notable as the first (non-avian) dinosaur eggs discovered. The specimen in Age of Dinosaurs comes from the same region.