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Providing a remarkable peek into the dietary habits of a 110-million-year-old nodosaur, a team of paleontologists at the Royal Tyrrell Museum of Palaeontology, Brandon University, and University of Saskatchewan have revealed stomach contents representing the armored dinosaur's final meal of fern leaf fragments and various plant fossils preserved right down to the cells.
This one-ton type of ankylosaur, officially known as Borealopelta markmitchelli, was first discovered back in 2011 during mining operations near Fort McMurray in Alberta, Canada. Mummified in the thick mud of an ancient sea, the fossil was found upside down and in pristine condition for a creature that once roamed the dense primeval forests of North America in the middle of the Cretaceous period.
Following a meticulous six-year excavation and restoration of its intact skin and bones by museum technician Mark Mitchell, the spiky nodosaur was put on display at the Royal Tyrrell Museum of Palaeontology in Alberta in 2017. A new study detailing the results of the scientists' research was published Tuesday, June 3 in the online journal, Royal Society Open Science.
According to the paper, analysis of the soccer ball-sized cololite (petrified stomach or intestine contents) shows "well-preserved plant material dominated by leaf tissue (88 percent), including intact sporangia, leaf cross-sections and cuticle, but also including stems, wood and charcoal. The leaf fraction is dominated (85 percent) by leptosporangiate ferns (subclass Polypodiidae), with low cycad–cycadophyte (3 percent) and trace conifer foliage."
This documented study represents the most detailed, well-supported direct evidence of plant-based diet ever unearthed in an herbivorous dinosaur. Apparently this hungry nodosaur was a bit of a picky eater, preferring the soft leaves of certain low-lying ferns and mostly avoiding common cycad and conifer leaves. In total, researchers observed 48 microfossils of pollen and spores including moss and liverwort, 26 club mosses and ferns, two flowering plants and 13 conifers.
"The finding of the actual preserved stomach contents from a dinosaur is extraordinarily rare, and this stomach recovered from the mummified nodosaur by the museum team is by far the best-preserved dinosaur stomach ever found to date," said co-author Jim Basinger, a geologist at the University of Saskatchewan.
"When people see this stunning fossil and are told that we know what its last meal was because its stomach was so well preserved inside the skeleton, it will almost bring the beast back to life for them, providing a glimpse of how the animal actually carried out its daily activities, where it lived, and what its preferred food was."
These findings are an exceptional time capsule of the armor-plated beast's interaction with the land and its environment. Charcoal remnants inside its stomach indicate it was probably dining in a region struck by wildfires, since it's well known to paleontologists and paleobotanists that forest fires were a normal part of the ecosystem during the Cretaceous period, with low-growing ferns being the predominant plant life to thrive following vast conifer fires.
By investigating growth rings and maturity of much of the plant material, researchers theorized that the nodosaur's demise likely happened sometime between late spring and mid-summer. Digestive gizzard stones, similar to the ones ingested by birds, also populated the creature's stomach contents.
"We could see the different layers of cells in a leaf fragment including the epidermis with the pores, called stomata, through which plants take in carbon dioxide," study co-author David Greenwood told CNN. "We could also see the surface patterning of the epidermis cells, which was like a jigsaw pattern that we see on many living ferns.
"The discovery of charcoal together with a fern-filled stomach opens a window into the biology of this large herbivorous armored dinosaur as it suggested Borealopelta was likely a keystone herbivore that shaped the landscape by its grazing, and that it also grazed on the ferns growing in open areas created by wildfires. That is so cool."