In 2011, a worker at an oil sands mine in
Alberta, Canada, made one of the most exciting dinosaur discoveries of the 21st century. While digging up a cliffside, the worker’s
excavator struck an unusually hard object, peppered with large, tan splotches. He had just discovered the remains of a 110
million year-old nodosaur. Nodosaurs were a group of armored, plant-eating
dinosaurs that lived during the Late Jurassic and Cretaceous Periods. And paleontologists have been studying these
dinosaurs since the 1830s, but nobody had ever found a specimen like this one before. Researchers at the Royal Tyrrell Museum named
it Borealopelta markmitchelli, after the technician who spent over five years cleaning up the
fossil. It represented a completely new species - and
that was just the beginning. Although the dinosaur’s tail and a few other
parts were missing, everything that was left was amazingly detailed. There was a gorgeous skull; articulated neck
vertebrae; several leg and foot bones; and portions of the trunk and hip regions. But it was the rest of the fossil that made
international headlines. From the hips forward, Borealopelta had an
almost complete set of osteoderms. Osteoderms are bony plates that are embedded
in the skin, just like what alligators have today. Nodosaurs and many of their relatives had
backs that were covered in osteoderms, possibly for defense. Better yet, Borealopelta contained super-rare
remnants of softer body materials and even had traces of pigmentation, giving us important
clues about the animal’s color pattern. And the key to all of this exceptional preservation
was where Borealopelta ended up after it died and how it got there. Because, the strange thing is: It was found
lying on its back, in a marine deposit. In other words, it fossilized upside down,
under water. And a lot of other nodosaur fossils have turned
up in similar deposits, ones left behind by ancient waters. So how did these dinosaurs end up getting
buried at sea? The answer to that question is a gross-- but
also kinda cool -- process of decomposition called … wait for it! ... “bloat-and-float.” Nodosaurs belonged to a larger group of herbivorous
dinosaurs called the ankylosaurs. Scientists have found their remains on most
of the world’s continents, including Antarctica. And they generally divide ankylosaurs into
two major groups: the ankylosaurids and the nodosaurids - the nodosaurs. The ankylosaurids tended to have short, wide
skulls, and many sported bony clubs on their tails that were probably used as weapons. But nodosaurs didn’t have these clubs. Instead, many of them, including Borealopelta,
had long spikes on their shoulders and narrower snouts. Two of the oldest nodosaurs on record are
Gargoyleosaurus and Mymoorapelta. Both were around three meters long and lived
in the western U.S. during the late Jurassic Period. But nodosaurs persisted throughout the Cretaceous
Period, sticking around right until the Age of Dinosaurs ended 66 million years ago. And! Both nodosaurs and ankylosaurids often turn
up in marine fossil deposits. Now, you might remember from our video “When
Sharks Swam the Great Plains” that, from about 95 to 68 million years ago, a huge body
of water called the Western Interior Seaway split North America in half. And earlier in the Cretaceous, much of west-central
Canada and the upper Great Plains were covered by the Mowry Sea, an extension of the Arctic
Ocean. So, there was a lot of available sea for the
armored dinosaurs to end up in. For example, take the nodosaur known as Niobrarasaurus. It’s known exclusively from the late Cretaceous
marine deposits of western Kansas. And some of its fossils even bear the tooth-marks
of ancient sharks. And lots of other armored ankylosaurs-- including
nodosaurs -- have been found in marine deposits from places like Queensland, Australia and
James Ross Island, Antarctica. One species was even found in California with
fossilized oysters encrusted on its bones. And then we have Borealopelta, the spectacular
nodosaur that those Albertan miners came across. Its remains were discovered in the Early Cretaceous
Clearwater Formation, where the fossils of marine reptiles like plesiosaurs and ichthyosaurs
often turn up. But scientists had never found any dinosaur
material out there -- until Borealopelta. So what happened? Well, after its death, Borealopelta’s
corpse hit the sea floor around 200 to 400 kilometers away from the closest shoreline. And it landed upside-down, which turns out
to have been a common fate for nodosaurs. Computer simulations suggest that these top-heavy
animals would’ve flipped over pretty easily while floating in the water. So, below the waves, Borealopelta came to
rest in a layer of stagnant, oxygen-poor mud. Traces of burrowing sea creatures were found
nearby, but paleontologists found no evidence that the dinosaur’s body was scavenged. And when it was discovered, Borealopelta was
encased in a tomb of hard rock called a concretion. As its body decayed, carbon dioxide and other
substances were released, which changed the chemistry of the water inside that mud around
the carcass. Soon enough, a tough layer of siderite--a
type of iron carbonate--formed, protecting the dinosaur’s remains. But how did it get so far away from the coastline? After all, Borealopelta was heavily armored
and short-legged, so it was probably a terrible swimmer - and it lived on land, anyway. So there’s no reason to think the nodosaur
swam to its watery grave. It’s more likely that the dino’s body
was washed out to sea. Sometimes, after an animal dies and bacteria
start breaking it down, gasses build up inside the corpse. And if the carcass ends up in a body of water
while that’s happening, it might start bobbing around at the surface. Scientists call this phenomenon “bloat-and-float.” Eventually, those gases escape, the body stops
floating, and it sinks to the bottom. And no matter where an animal dies, there’s
a good chance its remains will get scattered around after death. But the concretion around Borealopelta kept
most of its skeleton together. Better yet, the rocky shell helped the dinosaur
retain its three-dimensional shape, even as layers of sediment piled up on the carcass
over time. Between the bloat-and-float process and the
seafloor environment where it landed, Borealopelta kind of hit the jackpot in terms of preservation. For example, along with those osteoderms,
experts found that the fossil was also covered with tiny, polygonal scales on much of its
skin. And delicate skin structures were spread out
across the skull, neck, back, hips, and even its legs. Plus, many of the dinosaur’s osteoderms--along
with other parts of the body--were coated in a dark, grey material. This stuff has been identified as a kind of
organic film, and it’s loaded with the chemical traces and byproducts of keratin. Keratin is a key ingredient in fingernails,
hooves, feathers, and hair. And some modern reptiles, like alligators,
have keratin sheaths over their osteoderms. Unfortunately, keratin often vanishes without
a trace during the fossilization process. But the organic film on Borealopelta preserved
the original three-dimensional structure of the keratin sheaths that covered and lengthened
its bony osteoderms when the dino was alive. The ones on Borealopelta’s shoulder spikes
are 10 millimeters thick in some places. And make up about 25 percent
of the total length of each spike. So this gives us a clearer picture of what
the nodosaur actually looked like! But wait there’s more! The film of keratin wasn’t even the most
spectacular aspect of this fossil. This dinosaur had preserved evidence of coloration,
and it came in an unexpected pattern. Some of Borealopelta’s scales bear the chemical
hallmarks of a pigment called pheomelanin. Judging by these traces, it appears that most
of the dinosaur’s back was reddish-brown, while its underside was pale. That means Borealopelta could’ve been countershaded,
or darker on its upper side and lighter on its underside. Countershading can make animals much harder
to see, because of the way shadows help us perceive objects. When sunlight hits a three-dimensional body,
it tends to look light on top and dark on the bottom. So, if these creatures are lit from above,
they’ll look almost uniform in color -- their dark backs will be illuminated and their light
underbellies will look darker. Because of that, predators might not even
recognize countershaded animals as three dimensional objects. Visually, they’re harder to make out. This would’ve been really useful for Borealopelta,
because even though it was really big -- like 1,300 kilograms --- back in the
nodosaur’s heyday, massive carnivores stalked North America. One of them was Acrocanthosaurus, a predator
that measured 11 meters long and could’ve weighed up to 7.25 metric tons. With enemies like that on the prowl, Borealopelta
may have benefitted from a little camouflage. Without the exceptional preservational environment
created by the concretion - and the whole bloat-and-float thing in the first place - we
wouldn’t have any clue what color this huge dino was - or what it ate. And that brings us to a soccer ball-sized
lump found in Borealopelta’s abdominal cavity. In 2020, Royal Tyrrell paleontologist Caleb
Brown and his colleagues recognized this lump as a cololite, which is a hunk of fossilized
intestinal contents. Even though Borealopelta had ended up in a
marine deposit, this cololite was loaded with bits and pieces of land plants. Fossil sites in other parts of Canada tell
us that central Alberta was home to a wide variety of terrestrial plants in the early
Cretaceous, with conifer forests dominating the landscape. But it doesn’t look like Borelopelta was
too keen on conifers. Leaf tissue makes up 88% of all the plant
matter that was identified inside the cololite, and the vast majority of those leaves came
from ferns. Which is interesting! Because, scientists had always assumed that
nodosaurs--with those long, narrow snouts--were picky eaters. Instead of chowing down on mixed foliage indiscriminately,
the dinosaurs would’ve carefully plucked their favorite plants. And Borealopelta’s gut contents look like
evidence of this. But they also point to something surprising
about the environment that it lived in. Inside the cololite, the researchers discovered
a few samples of charcoal that the dinosaur apparently swallowed. In fact, burned plant fragments represent
6% of the botanical material in the cololite. And perhaps that says something about Borealopelta’s
feeding behavior. Researchers think wildfires were quite common
during the Cretaceous. When Borealopelta was alive, oxygen may have
made up around 30% of the Earth’s atmosphere, compared to just 21% today. And when these natural disasters happen, ferns
often bounce back faster than other plants do. For a brief period, ferns may actually dominate
a post-fire landscape as the environment recovers. So if Borealopelta was a picky eater with
a taste for ferns, then maybe the dinosaur was attracted to wildfire-stricken areas where
these plants were thriving. Between the remnants of keratin and its preserved
dietary clues, Borealopelta might be the most significant nodosaur fossil ever found. And just think, the dinosaur could’ve been
lost to us forever if it hadn’t bloated and floated across an inland sea. In death, this creature beat the odds, evading
scavengers and the ravages of fossilization before it survived the mining process and caught
an equipment operator’s eye. By doing all this, it’s given us a bounty
of dinosaurian knowledge. So here’s to Borealopelta markmitchelli,
an improbable ambassador from the early Cretaceous. Thanks to paleontologists Caleb Brown and
Donald Henderson of the Royal Tyrrell Museum in Alberta, and Jakob Vinther of the University
of Bristol for their help with this episode. And thanks to this month’s Eontologists
for floating around with us: Lucan Curtis-Mahoney, Sean Dennis, Jake Hart, Jon Davison Ng, Patrick
Seifert, and Steve! You can become an Eonite by pledging your
support at patreon.com/eons. Also thank you for joining me today in the
Konstantin Haase studio. Be sure to subscribe at youtube.com/eons for
more adventures in deep time.
As a 22 year old dinosaur kid, PBS Eons is one of my favorite YouTube channels by far
Awesome loaded information, wicked cool!
We went and saw this fossil the year it was put on display in Drumheller. It's absolutely amazing in person. Gave me chills
It's so crazy that we can make all of these super in depth conclusions from like, almost no information.
If you told me we found a dinosaur in the middle of what used to be an ocean, with some charcoal in his stomach, I would not have been able to explain any of that, let alone draw the conclusions they came up with.
This was super cool! Highly recommend.
Borealopelta
I love PBS Eons videos. They’re the perfect amount of interesting yet soothing to put me right to sleep at night. I pick a different video every night and I’m usually asleep 3 minutes in. I finish them in the morning while I’m getting ready lol
does anyone else absolutely hate the upwards infelction of every youtube info video host these days? it's so goddamn annoying. just speak normal. don't inflect upwards at the end of every sentence.
Swimming practice for itđź‘Ť