Researchers have made an amazing discovery at an oil sands mine north of Fort McMurray, Alberta. They found a dinosaur fossil so well-preserved that it’s one of the best of its size ever discovered.
This rare find not only preserved the dinosaur’s armor plates (osteoderms) in their original positions, but also the remains of its skin, keratin sheaths, and even its last meal in the stomach. It’s a truly remarkable glimpse into the past, offering scientists a rare opportunity to study a dinosaur in extraordinary detail.
Discovery of the Holotype Specimen
On March 21, 2011, a miner named Shawn Funk discovered a rare fossil at the Millennium Mine, located 30 kilometers north of Fort McMurray, Alberta.
While digging through Wabiskaw Member sediments, an excavator struck the fossil, prompting the team to contact the Royal Tyrrell Museum. In accordance with Alberta’s fossil laws, the specimen became the property of the provincial government.
On March 23, 2011, scientists from the Royal Tyrrell Museum, Dr. Donald Henderson and Darren Tanke, arrived to examine the fossil.
They initially thought it was a marine reptile, as no land animals had been found in the oil sands before. However, Tanke quickly identified it as an ankylosaur dinosaur, which had likely been washed out to sea after death.
After completing mine safety training, museum staff and Suncor workers spent 14 days recovering the fossil. Most of it was embedded 26 feet up a 39-feet cliff, with several pieces already broken free.
While lifting the main rock containing the fossil, it broke into pieces. Museum staff stabilized the fragments with plaster and transported them to the Royal Tyrrell Museum.
Technician Mark Mitchell spent six years preparing the fossil for study, supported by the National Geographic Society. (ref)
In recognition of his work, the species was named Borealopelta markmitchelli. The fossil was displayed to the public on May 12, 2017, as part of the “Grounds for Discovery” exhibition. (ref) The museum’s curator, Dr. Henderson, told The Guardian that he believed it was a literal “one in a billion” find. (ref)
Preservation of Borealopelta
Borealopelta is a large nodosaurid ankylosaur that’s about 18 feet long and weighs 1.4 short tons. The specimen is extraordinary due to its three-dimensional preservation, including soft tissues.
Unlike many small dinosaurs that flattened during fossilization, this specimen remained largely intact. It likely sank upside-down onto the sea floor after death, allowing the top half to be buried quickly and preserving its natural appearance without distortion.
In Dr. Henderson’s published study, the Borealopelta specimen preserved many small armor plates along its body.
It had a straight tail, not a tail club, and long spines protruding from its shoulders that resembled bull horns. Analysis of its skin and scales suggests it may have been reddish-brown with a counter-shaded pattern for camouflage.
Their phylogenetic analysis, based on 480 different trees, showed that Borealopelta grouped with Pawpawsaurus and Europelta as part of a group of Albian nodosaurs. Hungarosaurus was the next closest relative.
Also, the spikes of Borealopelta may have served two purposes: as defensive weapons and as display structures for attracting mates or species recognition. (ref)
How It Got Preserved among the Albian Marine Sediments
According to Dr. Henderson’s study, the Borealopelta was preserved in marine sandstones and shales of the Wabiskaw Member, Clearwater Formation, dating to about 110–112 million years ago during the Early Cretaceous.
At that time, the area was covered by the Western Interior Seaway, an inland sea stretching from the Arctic to the Gulf of Mexico.
The Borealopelta holotype was likely washed out to sea, possibly during a flood. It was initially believed that the carcass floated on its back for weeks, bloated with gases, before sinking after the gases were released. (ref)
Dr. Henderson’s research indicated that about 5.9 inches of sediment covered the body before fluids escaped, leaving marks in the sediment. Sand filled the body, and a hard shell formed around it that stopped scavengers and kept the body, scales, and armor plates intact.
In 2020, Asier Larramendi, research director of Eofauna Scientific Research, and his team disagreed with the floating hypothesis.
They noted that ankylosaurs would need a density similar to modern birds, which they didn’t have. They suggest instead that Borealopelta was washed out to sea, drowned while trying to stay afloat, and then sank. (ref)
The well-preserved Borealopelta holotype provides valuable clues about how dinosaurs lived and looked in life. This finding is an important step in understanding the ancient world and shows just how much we can still learn about the dinosaurs that once roamed the Earth.
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Nancy Maffia
Nancy received a bachelor’s in biology from Elmira College and a master’s degree in horticulture and communications from the University of Kentucky. Worked in plant taxonomy at the University of Florida and the L. H. Bailey Hortorium at Cornell University, and wrote and edited gardening books at Rodale Press in Emmaus, PA. Her interests are plant identification, gardening, hiking, and reading.
