Kids Unearth a Teenage ‘T. rex’ While Hiking in North Dakota

Judging from the fossils, this “Teen Rex” was 25 feet long and weighed about 3500 pounds while alive.

By Nick Keppler |
Kaiden Madsen, Liam Fisher, and Jessin Fisher pose in front of their latest find. Their father, Sam Fisher, texted this photo to his high school classmate Tyler Lyson, setting the stage for a remarkable discovery.
Kaiden Madsen, Liam Fisher, and Jessin Fisher pose in front of their latest find. Their father, Sam Fisher, texted this photo to his high school classmate Tyler Lyson, setting the stage for a remarkable discovery. / Sam Fisher

In the summer of 2022, Sam Fisher was trekking through the Hell Creek Formation with his sons Liam and Jessin, ages 7 and 10, and their cousin Kaiden Madsen, 9. They spotted a fossil sticking out of a rock formation—not an unusual occurrence in this section of the Badlands of North Dakota. But this find turned out to be a rare partial skeleton of a Tyrannosaurus rex in its adolescence—and it’s about to go on display at the Denver Museum of Nature and Science.    

The Hell Creek Formation, owned by the federal government, stretches through four western states. Over the last 65 million years, a nexus of water activity and clay, mudstone, and sandstone sediments turned it into a plentiful fossil bed. Not just dinosaur bones, but remains from an array of amphibians, fish, invertebrates, sharks, rays, and pre-historic mammals have been plucked from its sandstone and shales. 

The Hell Creek badlands of southwestern North Dakota, where the juvenile ‘T. rex’ skeleton was discovered by a trio of young fossil hunters.
The Hell Creek badlands of southwestern North Dakota, where the juvenile ‘T. rex’ skeleton was discovered by a trio of young fossil hunters. / Dr. Tyler R. Lyson

Sam Fisher contacted Tyler Lyson, a high school classmate who happens to be a vertebrate paleontologist at the Denver Museum, according to the museum’s magazine. With permission from the Bureau of Land Management, Lyson led an excavation of the then-unidentified dino. He told The New York Times that he thought the bones belonged to a duck-billed dinosaur until he discovered the distinct jawbone of a T. Rex. The fossils were packed in plaster and transported to the museum via truck and airlift. 

Judging from the remains, this “Teen Rex” was 25 feet long and weighed about 3500 pounds while alive, making it seem positively gangly compared to the average adult, which stretched to 40 feet long and weighed about 8000 pounds.

A lower jaw, complete with several dark teeth (pointing to the right in the photo) is slowly uncovered. Archaeologist's brush for scale.
A lower jaw, complete with several dark teeth (pointing to the right in the photo) is slowly uncovered. Archaeologist's brush for scale. / Dr. Tyler R. Lyson

The rarity of pre-adult fossils has left paleontologists with an incomplete picture of Tyrannosaurus rex’s youth, but the record indicates it grew a lot—gaining 1680 pounds per year to develop from a border collie-sized hatchling to a three-stories-tall terror lizard.

The exhibit featuring Teen Rex, along with a documentary about the discovery, opens at the museum on June 21.

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