DALLAS — On a sweltering afternoon this spring, Stephen Kruse walked along a dry creek bed with a backpack full of fossils.
An avid hobbyist, Kruse has been interested in dinosaurs and prehistoric creatures ever since he hunted rocks with his brother as a child. That afternoon, he was hiking by himself near the North Sulfur River, about 80 miles northeast of Dallas. It was an area he had combed through several times.
He was starting to get tired. As the day lengthened, Kruse searched for a way to get back to his white Chevy Suburban. He decided to look for a shortcut a quarter of a mile away. “Best decision I’ve ever made,” he said.
Just 100 yards into the rocky creek bed, he saw it: a 5-6 inch black vertebra, a piece of the spine of a prehistoric creature.
Kruse followed the path upstream, searching for the rest of the creature. “When I turned that corner,” Kruse recalled, “he was just sitting there, sticking out of the wall.”
Kruse had found fossilized bones belonging to a mosasaur, a 30-foot sea lizard that ruled the seas around 80 million years ago.
Recently, paleontologists from the Museum of Nature and Science in Perot extracted the fossils from the soft, clayey rock of the creek bed. They excavated parts of the mosasaur’s skull, lower jaws and several vertebrae from its spine.
This is important work for scientists: even if the mosasaurs are not around today, learning more about the past can give us a window into the present. Finding out what these creatures ate and how they interacted with their environment can help paleontologists refine their picture of what life was like millions of years ago.
“You get this beautiful story of why things are the way they are here, by reconstructing that story in your time,” said Dori Contreras, curator of paleobotany at the Perot Museum.
A river rich in fossils
In the 1920s, farmers had a problem with the North Sulfur River. Bends and bends in the river caused farmland to flood when it rained. So the river was channeled, or straightened, to help the water flow faster.
The channeling of the North Sulfur River did more than drain the marsh. This affected the way the water eroded the edges of the bank. To this day, rainwater is rapidly breaking down the soft rock, revealing pieces of the past.
“It’s perfect for fossil hunters, because when it rains, this thing will flood, tear it all up,” Kruse said. “And because it’s cut at one level, the next day the water is gone and you can just come here and hike.”
Kruse said he often finds fossils in streams near the river valley. Many are descended from mosasaurs.
This is not surprising for Ron Tykoski, director of paleontology at the Perot Museum and curator of vertebrate paleontology.
He says that 80 million years ago almost all of central Texas was under water. The warm, shallow sea water and abundance of food in the area created the perfect habitat for creatures like mosasaurs.
Prehistoric great white sharks
Tykoski said mosasaurs were like great white sharks or killer whales from prehistoric times. As large marine predators, they fed on turtles, sharks and even each other.
“Imagine a 30-foot-swimming, pointy-nosed Komodo dragon with flippers and a forked tail,” he said.
The mosasaur fossils Kruse found protruded from the rocky creek bed. Once Kruse realized the bones could be more than a few vertebrae, he ran upstairs and called Mike Polcyn, who Kruse knew was a paleontologist and mosasaur expert at Southern Methodist University.
Polcyn helped Kruse contact Tykoski at the Perot Museum. Tykoski and his team obtained permission from the Upper Trinity Regional Water District to recover the fossils.
Tykoski visited the area in June to get an idea of how many fossils there were and how easy they would be to remove. He realized that the soft rock would be fairly easy to remove with picks and shovels, revealing the fossils beneath.
Fossil Mining 101
Excavation began in mid-July in a dry creek bed lined with brown and gray clay rocks.
Every day, Tykoski, accompanied by paleontologists from Le Perot, arrived early to beat the heat. They were joined by a small entourage, including a museum photographer, a videographer and Kruse.
Removing the remains of a 30-foot lizard from a creek bed is no easy task. To extract the fossils, Tykoski and his team had to dig into the rock using picks and shovels.
They injected plastic and acetone glue into the bone cracks to prevent the fossils from shattering. They also used finer tools like probes and paintbrushes to carefully remove chunks of gray rock once they got closer to the exposed fossils.
To distinguish rock from bone, Tykoski and his team lightly tapped a rocky area with a metal probe. If it was soft rock, it broke away from the creek bed with a small force, without a sound. If it was bone, it made a high-pitched metallic rattle against the probe.
After the fossils were mostly exposed, the team dug under them, creating a sort of mushroom shape, said Mariah Slovacek, Paleo Lab collections manager at Perot, who was on site.
When they had their mushroom, the team made casts called “field jackets” on the fossils to hold everything in place, like fixing a broken arm or leg. Each campaign jacket was made of hessian dipped in plaster. Once the plaster had hardened, the team could turn it over and transport the fossils in sections to the creek bed.
The whole process took about six days. Tykoski said digs like this happen sporadically. Sometimes he gets a bunch of calls about exposed fossils after the spring rains. Other times he goes years without finding anything worth exploring.
Contreras said she loved every part of the fieldwork. “It’s like a puzzle: the whole time you’re working, you never know where it’s going to take you,” she said. “And so, as you dig deeper, you uncover more, you find more.”
Rithvik Shroff, 17, is a high school summer intern who was invited to dig. He said it was hard to maintain stamina and stay cool, but seeing the fossils come out of the ground was worth it.
“I mean, you see them in the museum, but you actually come here and see how they dig up… What does it look like?” said Shroff. “It’s really cool.”
The present, sitting on the past
Tykoski and his team pulled several mosasaur bones from the creek bed last week. But they haven’t finished searching this lizard.
During their initial investigation, Tykoski and his team noticed that more sea lizard bones were protruding from the creek bed. But they couldn’t reach them without stomping on the jaws they had already found.
Tykoski said the team plans to return in the fall with better gear and an updated game plan to remove the creek bed and reveal the rest of the mosasaur.
Once they have all the fossils, they can compare them to other mosasaur skeletons to see how the creatures have evolved over time, or study this mosasaur’s teeth to figure out what it ate in the middle of it. a prehistoric landscape of creatures.
It’s not the first — nor the second — mosasaur that Perot paleontologists have discovered in the Dallas area. It is an excellent example of the living remnants of our prehistoric past that lie beneath us.
“We have a wonderful, rich natural history right in the palm of our hands,” Tykoski said.
In the meantime, the fossils are at the collection center of the Perot museum, snug in their field jackets. Tykoski said he won’t be able to see them again until he and the team remove the remaining rock from the fossils and begin their study.
“You can peek at the Christmas presents,” Tykoski said, “and then you have to put them away again.”
Adithi Ramakrishnan is a science reporter at the Dallas Morning News. His scholarship is supported by the University of Texas at Dallas. The News makes all editorial decisions.
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