Dinosaur eggs

Amanda Copenhaver uses the BTMC’s GE Light Speed CT-Scanner to take thin vertical X-rays of a nest of fossilized dinosaur eggs.

The email had an urgency to it, even if it concerned something that was 75 million years old and well beyond the need for an emergency response.

“We're CT-scanning our dinosaur eggs at the hospital in Choteau tomorrow at 10:30 a.m. We’d love [you] to do a press release/article on the whole event. Would you like to join us?” wrote Stacia Martineau, a Bynum-based Two Medicine Dinosaur Center field instructor and program coordinator.

The following day at the Benefis Teton Medical Center entrance a smiling procession followed Martineau and her colleague Patrick Wilson who carried the exposed dino egg nests cradled in their plaster of Paris “jackets” to the radiology department.

Paleontologist Dave Trexler of Bynum explained the significance of the dinosaur egg nests while everyone watched Amanda Copenhaver and Amber Dahl operate BTMC’s GE Light Speed Computed-Tomography Scanner to build ultra-thin X-ray slices taken through each egg nest.

It was all the more surreal, when a recorded reminder to “Breathe in, hold your breath,” could be heard in the background as the scanner peeked inside the rare objects from the late Cretaceous geologic era for 70 seconds.

“This is a new type of eggshell. It doesn’t match others. It’s different,” Trexler said. “We suspect they are from medium to large-sized dinosaurs, perhaps from a ceratopsian (horned dinosaur) or a tyrannosaur, (theropod dinosaur). No one has ever identified eggs of those dinosaurs.”

According to Trexler, dino eggshell collections may contain shells from the great Tyrannosaurus Rex, but no one has published that find in the journal of the Society of Vertebrate Paleontology. Trexler hopes to identify the eggs and publish a discovery about the egg nests that the Two Medicine Dinosaur Center staff has been preparing since the dig site was opened in 2015 west of Choteau.

He said the only way to identify what dinosaur laid an egg is to find an egg with an embryo preserved inside. The CT-scanner is a tool to identify what is inside an egg without breaking into it, that is, in a nondestructive way.

“We’ve got a new egg taxon (group) and we’re looking for embryos to identify it, as least to the family level,” Trexler said. Usually fossil eggshells are found as scattered fragments, so finding a preserved, albeit, a cracked or crushed fossil egg, presents a rare opportunity, he added.

His mother, the late Marion Brandvold, discovered bones of baby dinosaurs in 1978 west of Choteau, which led to the concept that dinosaurs fed and monitored their hatched offspring, rather than laying eggs like turtles and having the hatched young fend for themselves.

Pore patterns and eggshell microstructure are different in each species, and embryonic animals have teeth, a third way to identify the species, Trexler said.

Copenhaver and Trexler discussed how the digital information would be transferred and she smiled as she quipped, “My son will be so mad he is not here to see this.” He is an avid dinosaur fan, she said.

Trexler said three outcomes could occur after the scanning: They see nothing because the eggs were sterile, they see something they can identify, that they can then match eggshell to embryo, or they see something, but it is unrecognizable. The last result could mean taking another step, once funding is secured, to scan the egg nest at a much higher resolution in an industrial scanner.

“If nothing else, this will tell us what to spend money on,” he said. The Two Medicine Dinosaur Center is a 501(c)(3) tax-exempt organization. Visit the website, www.tmdinosaurcenter.org for more information or to make a donation. The mailing address is P.O. Box 786, Bynum, MT 59419.

“I see some slight density differences. I see cracks, but microscopic details can be pretty distinctive to the egg producer,” Trexler said after a closer look at one of the scans. The number of layers within the eggshell, for instance, and the arrangements of the minerals that make up the layers, vary from group to group, he said.

It will be a long process, but it has been a long process already, Trexler said, as he described his first notice of eggshell fragments exposed on a hill west of Choteau in 2012. The site was worked on for a time, but they closed it until 2015 when more work resulted in the egg nests being found. “We did not have enough staff,” he said. As it was, the digging in 2016 revealed that the site was about four times the size they had originally thought with more egg nests discovered.

With the jacketed specimens brought to the Bynum lab, more tedious work was done last summer to expose the eggshells.

His pride in the work the staff is doing showed as Trexler said, “The good part is we’ve got type specimens in our collection no one has ever seen. It does the heart good. We are putting another piece of the universe together.”