Revealed: Armored Dinosaur’s Last Meal

Illustration of Borealopelta markmitchelli dinosaur, by Julius Csotonyi. Researchers worked with Csotonyi to get details right, including accurate portrayal of the vegetation and things like the nodosaur’s keratin horns. (© Royal Tyrrell Museum of Palaeontology)

(CN) — When the 2,800-pound nodosaur enjoyed a meal of fern leaves, stems and twigs more than 110 million years ago, it likely didn’t expect to die soon afterward.

Within a day or two, the armored herbivore — camouflaged by countershading and about the size of a Volkswagen Beetle — washed out to sea, and its remains were entombed under a deposit of oil sands in northeastern Alberta, where a Suncor Millennium miner named Shaun Funk discovered the creature in 2011.

“The preservation is very, very good,” said David Greenwood, the Brandon University ecologist who co-led the stomach research. “It’s about as good as it gets.”

And because the nodosaur’s remains were practically “mummified,” Greenwood and a team of scientists were able to study its last meal, barely digested, giving them a glimpse into the behavior, diet and habitat of the Early Cretaceous nodosaur.

After three years with the stomach, the researchers published their findings Tuesday in Royal Society Open Science, an open-access journal.

“Before this study, our understanding of what these animals ate, of what any herbivorous dinosaur ate, was mostly based on theory: looking at the teeth, looking at jaw musculature, and the kinds of plants that would have been around the time the dinosaurs lived,” Greenwood said.

That changed in part due to Alberta’s fossil laws, which require mining companies to immediately report discoveries to the government. Suncor took the newly discovered dino to the Royal Tyrrell Museum of Palaeontology, where preparation lab technician Mark Mitchell spent more than 7,000 hours over six years separating the specimen from its rocky surrounds, one chip at a time.

For this, Mitchell earned his place in the new species’ name: Borealopelta markmitchelli.

Tyrrell scientist Caleb Brown and Brandon University biologist David Greenwood together led five other scientists who took the stomach mass — “about the size of a basketball,” Greenwood estimates — and cut and polished segments thin enough to examine under a microscope.

“From all that, we were able to figure out that its last meal was dominated by ferns,” Greenwood said.

Though its landscape was populated with plentiful cycads and conifers, the picky nodasaur preferred leaves from the leptosporangiate family, today’s largest group of ferns. Some slides featured bleached, pale plant material, but the overwhelming majority featured fresh plants, suggesting that the dinosaur had hardly begun digesting its food when it died.

“The bigger problem is how old it is,” Greenwood said of identifying the stomach’s content. “Because we’re dealing with a time in the history of life on earth where many of the plants are extinct today.”

After counting hundreds of thousands of specimens, the team concluded that the stomach contained 88% chewed leaves and 7% stems and twigs. The remaining 5% included miscellaneous materials as pollen, spores, mosses, gizzard stones — not unlike the ones found in modern animals such as geese, pigeons and sea lions — and, notably, charcoal.

“Where this animal was grazing had recently, within the last year or two, experienced a wildfire,” Greenwood said. “That’s telling us something more about the ecology of the animal, the way it lived its life.”

An area recovering from wildfire is open for easy grazing, just as today’s moose, deer and elephants prefer to do, according to Greenwood. 

“And maybe this animal was doing that too; it was choosing an area that was recently burnt because it’s more open. It’s a big animal, the size of a Volkswagen Beetle,” Greenwood said. “It’s this lush, good-quality food for the nodosaur. So maybe we’re seeing that kind of ecological knowledge, that not only does this animal prefer to eat ferns, but maybe it was preferring this … nutritious regrowth, after a fire.”

Greenwood remembers this discovery as his “Aha!” moment.

“The charcoal was big; that really opens a window in time to what this animal was doing in the landscape, of how it may have played a role in shaping the landscape,” Greenwood said. “We think of animals as ecological engineers. Keystone species are animals who shape how the whole ecosystem functions, through their feeding. … By how much it ate and where it ate, it shapes the vegetation.”

The twigs found in the nodosaur’s stomach provided the team a rare view into when it died — because trees form growth rings slowly over time, cross-sections featuring incomplete rings can tell researchers what time of year the plant was eaten.

In this nodosaur’s case, it must have died between the late spring and mid-summer.

Brown and Greenwood received funding from a host of scientific foundations including the Canada Foundation for Innovation, Research Manitoba, the National Geographic Society and Olympus Canada. The research team included Royal Tyrrell Museum paleontologists Dennis Braman and Donald Henderson, Brandon University research technician Cathy Greenwood and graduate student Jessica Kalyniuk, and University of Saskatchewan geologist Jim Basinger. 

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