And now we know what it ate for its last meal.
Dinosaur tummies and evidence of their diets are rarely preserved. Sometimes seeds and twigs have been found in the intestines of dinosaur remains, but never conclusive evidence of the actual plants.
In this case, a muddy grave enclosed a dinosaur and preserved it so well that even its stomach contents remain to tell it was a picky eater.
“The leaf fragments and other plant fossils were preserved down to the cells,” said David Greenwood, study fellow, Brandon University biologist and University of Saskatchewan adjunct professor, in an email.
The Nodosaur, known as Borealopelta land mitchelli, was found in 201
After his death, the dinosaur’s remains ended up in what was an ancient sea, landing on its backs in the muddy seabed and remaining undisturbed until nine years ago.
It has been on display at the Royal Tyrrell Museum of Palaeontology in Alberta since 2017. The fossil was revealed after museum technician Mark Mitchell spent six years to accurately reveal the dinosaur’s preserved skin and bones from the marine cliff where it was enclosed.
In life, the dinosaur – a type of ankylosaur – weighed more than a ton. But it lived off plants and favored ferns, based on the contents of the stomach. The piece that resembles the stomach is about the size of a football.
“The discovery of the actual preserved stomach contents from a dinosaur is unusually rare, and this stomach recovered from mummified nodosaurs by the museum team is by far the best-preserved dinosaur stomach found to date,” says Jim Basinger, study member and University of Saskatchewan geologist .
“When people see this amazing fossil and hear that we know what its last meal was because the stomach was so well preserved inside the skeleton, it will almost revive the animal to life for them and give a glimpse of how the animal actually carried out its daily activities , where it lived and what the preferred food was. “
This discovery illuminates definitive evidence of what a large herbivorous dinosaur ate – in this case a bunch of chewed snake beans, some stalks and twigs. The details of the plants were preserved so well in the stomach that they could be compared with samples taken from modern plants today.
“We could see the different layers of cells in a leaf fragment including the epidermis with the pores, called stomata, through which plants absorb carbon dioxide,” Greenwood said. “We could also see the surface pattern of the epidermal cells, which was like a puzzle pattern that we see on many living ferns.”
A picky eater
This discovery changed what scientists know about the diet of such large herbivores, and the plant material revealed more about the dinosaur’s interaction with its environment.
This nodosaurie was picky. The researchers compared the contents of the stomach with fossil leaf studies from the same time period and region. The Nodosaur specifically ate the soft leaves of some ferns and largely neglected ordinary cycad and conifers.
In total, they found 48 microfossils of pollen and spores including moss and liverwort, 26 club mosses and ferns, two flowering plants and 13 conifers.
“The lack of ponytails and the rarity of cycads and conifers is surprising, given that these are very common in the surrounding flora,” said Caleb Marshall Brown, study author and curator of dinosaur systematics and evolution at the Royal Tyrrell Museum of Paleontology, in an email. “Even within ferns, it seems that Borealopelta may have had a preference for certain types of ferns, while ignoring others.”
Preservation of the plant material in the stomach suggested that the dinosaur died and was buried soon after eating. Based on growths and maturation for any of the plant material, researchers were able to determine that the dinosaur’s death likely occurred between late spring and mid-summer, Brown said.
With a side of charcoal
Then there is the issue of carbon, which was also found in the stomach. That probably meant it was grazing in an area affected by wildfires. Researchers know that forest fires were common in forests during the early Cretaceous period, 100 million to 145 million years ago. And after forest fires, ferns bloom low to the ground.
“When you think about it, it can actually be very meaningful,” Brown said. “If you are a nodosaur you can only feed near the ground. This new growth will also be more flavorful and have a higher nutritional content than established growth [like conifers]. As a result, many large mammal species that we are familiar with today will seek newly burned areas in both grasslands and forests, as they provide unique feeding opportunities. “
Wildfires probably occurred in the area where the nodosaur grazed during the six to 18 months, Greenwood said. There is enough time for lush ferns to show up.
“The discovery of charcoal along with a snake-filled stomach opens a window into the biology of this large herbivorous reinforced dinosaur, as it suggested that Borealopelta was probably a keystone herbivore shaping the landscape through its pasture, and that it also grazed on the ferns growing in open areas created by fires, Greenwood said. “It’s so cool.”
Paleobotany, which is the study of plant fossils, provides insight that dinosaur skeletons simply cannot, Greenwood said.
Gizzard stones, much like those swallowed by birds to help with digestion, were also found in the dinosaur’s stomach.
The researchers will continue to study the dinosaur to see what other secrets they can reveal, such as how this nodosaur could thrive and achieve such a large size with relatively low quality of food, Brown said. Greenwood’s graduate student, Jessica Kalyniuk, studies fossil plants from the Gates Formation in Alberta’s Rocky Mountain Foothills to learn more about the forests where the nodosaur lived.