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Mother’s Day Site helps unlock ancient mysteries while asking more questions

Jul 31, 2024

The Mother’s Day Site doesn’t give up its secrets easily.

For the last 30 years, crews have been doing the painstaking work of exposing dinosaur bones, wrapping them in plaster, and carefully removing them for further study.

Photo of several people digging on a rocky slope. — Work has been ongoing at the Mother’s Day Site in southern Montana for 30 years.

Researchers have found that the bones date to the Late Jurassic (~150 million years ago), and that most of them come from sub-adult individuals of the same species: Diplodocus. A site this big usually yields bones from a variety of species, not just one.

A species of sauropod, Diplodocus is a long-necked dinosaur with a small head, long tail, and massive body. An adult could be 110-feet long, but the specimens collected at the Mother’s Day Site are only about 75 percent of that.

illustration of dinosaurs with long necks and long bodies. — Life reconstruction of juvenile Diplodocus from the Mother's Day site with adults.

“This site is about science that’s ongoing,” said Jason Poole, Field Expedition Crew Chief and Paleontological Anatomy Specialist for Elevation Science Institute, a nonprofit organization dedicated to paleontology and earth science research, education, and outreach. “The best thing about this site is taking what we think we know and challenging that.”

He went on to say that when a site has so many individuals of the same genus and species, patterns emerge which can lead to new theories. For example, the bones show signs of similar injuries, which suggest certain behaviors. Over the years there have been ideas to explain such patterns, but those ideas have changed as more is learned.

“All of these are just pieces,” said Poole. “So the more pieces you can find to the story, the better you understand.”

Photo of man in blue hat bent over a partially revealed dinosaur bone. — A tibia from a Diplodocus slowly emerges at the Mother’s Day Site.

The Mother’s Day Site was discovered on Mother’s Day in 1994 by a volunteer with the Museum of the Rockies. In the six years following that first discovery, the MOR collected 600 bones. After that the Cincinnati Museum Center collected more than 2,000 specimens including the most complete and well-preserved juvenile sauropod skull in the world.

After many years, Cincinnati had enough material for its Dinosaur Hall, so the site was handed off to Elevation Science which invites the participation of volunteers of all ages to help reveal the secrets held there.

Volunteers come from as far away as Sweden, some for a day, others for a week or more. Many of them return year after year, fulfilling a lifelong dream.

“This site is good for education,” said Poole. The larger bones are less likely to break, and that builds confidence in people new to the field.

As the work continues, so do the discoveries -- such as dinosaur skin from juvenile sauropods.

Once removed from the site, the bones are shipped to the Cincinnati Museum Center where museum visitors can watch as workers remove the plaster, clean the pieces, and reassemble them. Because the bones were collected from public lands, they are publicly owned and available for scientific research.