Is the world’s largest Triceratops skull sitting in our collection?

On June 6th, 1929, renowned fossil collector Charles M. Sternberg sat writing in his journal in a Saskatchewan field camp recording the first day of his team’s summer fossil prospecting. He noted the work done, the area’s rock formations and the fossil specimens collected.

Of particular note was the first dinosaur fossil found, the partial skull of an exceptionally large Triceratops prorsus.

Referring to the bony frill around this horned dinosaur’s neck, Sternberg finished the journal entry dramatically: “This is the largest crest I have seen.”

Painting of a horned dinosaur

In this 1901 painting by Charles R. Knight depicting a lone Triceratops, the broad, bony shield that projected around the dinosaur’s neck is especially prominent. The body shape and pose reflect the early 20th-century view of dinosaurs as lumbering animals that dragged their tails. Image: Charles R. Knight, public domain.

Black-and-white photograph of a plastered fossil specimen in the field.

Charles Sternberg took this photograph of the Triceratops skull in the field. The two projections on the lower right are the brow horns. Today, most of the specimen is still covered in a layer of rock. Catalogue number: CMNFV 56508. Image: C. M. Sternberg, © Canadian Museum of Nature.

Fast-forward to 2015 and Canadian Museum of Nature dinosaur palaeontologist Jordan Mallon was reading Sternberg’s field journals.

Sternberg’s big crest comment caught his eye—and his imagination. Could this possibly be the largest Triceratops ever collected? What made the possibility particularly exciting is that the answer lay a hundred meters away in the museum’s collection.

The specimen still lay wrapped in the protective layers of plaster applied to it in 1929. Dr. Mallon proposed we prepare the specimen and put Sternberg’s observation to the test.

This is where I enter the story. I am the coordinator of our fossil preparation program, and so it’s now my job to ready the fossil for scientific examination by opening the plaster field jackets and preparing the fossil.

This will not be an easy task.

The skull is so large that when it was collected it was wrapped in two separate plaster field jackets. The larger, a 650-kg section, includes two thirds of the frill, the top of the dinosaur’s cranium, and the two long brow horns. A smaller, 400-kg section contains the remaining third of the Triceratops‘ frill.

Two fossil specimens on wooden supports in a workshop.

The two field jackets containing Charles M. Sternberg’s 1929 Triceratops prorsus specimen. The two brow horns are discernible in the shape of the larger jacket (left), against which is a board showing illustrations of this dinosaur’s skull. The smaller jacket (right) is shown following initial preparation of one side. Catalogue number: CMNFV 56508. Image: Alan McDonald, © Canadian Museum of Nature.

Preparing any fossil comes with its own challenges, but the preparation of the Triceratops skull will be especially difficult.

While completely wrapped in its field jacket, the larger portion of the skull is safely supported on all sides. However, we know that given the massive size and weight of the skull, the jacket might give way during opening if not properly supported from the exterior, and the skull could tear itself apart.

So, we decided to begin by opening the section containing the smaller portion of the frill. This is permitting us to assess the fossil’s overall condition and stability, informing our course of action for safely opening the larger field jacket.

A partially prepared fossil specimen with two areas exposed beneath its plaster jacket.

The smaller field jacket following the first round of plaster removal. The fossil frill is beginning to peek through in two places. Catalogue number: CMNFV 56508. Image: Alan McDonald, © Canadian Museum of Nature.

Now, five months into the project, progress has been slow but steady.

There is a layer of thick stone covering the fossil, and we’ve discovered that the majority of the underside of the frill is fractured but repairable.

With hard work, a lot of adhesive, and a little luck, we’ll know more in the upcoming months, and one day hope to add an exciting footnote to Charles M. Sternberg’s old journal entry.

Stay tuned for an update!

Image-5_Frill_Section

With one side of the plaster jacket completely removed, the frill is now completely exposed. The fossil’s heavily cracked surface was treated with a consolidant solution to strengthen it, but repair of the major breaks awaits. Catalogue number: CMNFV 56508. Image: Alan McDonald, © Canadian Museum of Nature.

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