Teen Rex Discovery Roars into the Denver Museum of Nature & Science

This Juvenile T. Rex Fossil was Found by Children!

Liam Fisher, Kaiden Madsen, and Jessin Fisher in front of the hill where they discovered their teenage T. rex skeleton in the Badlands of North Dakota. (Photo/Tyler Lyson)

This story begins in the Badlands near Marmarth, North Dakota. Up in this barren otherworldly landscape, a trio of young adventurers, eight-year-old Liam and 11-year-old Jessin, and their 10-year-old cousin Kaiden Madsen, were on a fossil-hunting adventure when they came across large bones weathering out of a sedimentary rock formation. The fossil was collected on land managed by the Bureau of Land Management under permit ND2023-0084. 

After snapping a few photos, the kids reached out to their father’s high-school classmate, Denver Museum of Nature & Science paleontologist Dr. Tyler Lyson, a hometown hero from Marmarth, North Dakota. Growing up in the town with a population of just 100 people, Tyler had started looking for dinosaurs bones in the area when he was just a kid.

responsive image

Dr. Tyler Lyson with Jessin, 12, and Liam, 9, Fisher and their cousin Kaiden Madsen, 11 in North Dakota's Badlands in Summer of 2023. (Photo/Rick Wicker)

Liam and Jessin loved Tyler so much that they even went so far as to dress up as him on Halloween! So, when the kids sent the photos of the dinosaur bone to Tyler, you can imagine that they were over the moon when he told them they had found a dinosaur fossil. While it wasn't initially clear what dinosaur the boys had found, Tyler made plans to come the next summer to dig up the fossil with the brothers, and that's when they found it was actually the remains of an extremely rare juvenile Tyrannosaurus rex!

Related story: Dinosaur-obsessed? Visit our Prehistoric Journey exhibition!

The Call to the Hometown Paleontologist

responsive image

Kaiden Madsen, Tyler Lyson and Jessin Fisher after realizing the dinosaur the kids found belonged to a Tyrannosaurus rex! (Photo/Natalie Toth)

The call to Dr. Tyler Lyson was met with enthusiasm and expertise, setting the stage for a remarkable collaboration between the young adventurers and the seasoned scientist. Looking at photos of the fossil, Dr. Lyson could tell that it was a dinosaur bone, but it wasn’t until later in the field when he and his team discovered that it was a T. rex fossil. Tyler also obtained the excavation permit for digging on public lands from the BLM and led the excavation.

responsive image

The discovery crew and Denver Museum of Nature & Science scientists in the excavation site in the Badlands of North Dakota in the Summer of 2023. (Photo/Rick Wicker)

Through a meticulous process that extended over 11 days, the team removed overlying rock and performed a careful excavation around the bones. After the excavation, the T. rex fossil was wrapped in plaster and burlap jacket and air lifted off the hill by a Black Hawk helicopter. The fossil was then transported on a heavy-duty trailer from the Badlands of North Dakota to the Denver Museum of Nature & Science for preservation.

Now that the Teen Rex fossil is here at the Museum, let's dive into the captivating world of the Teen T. rex and the many facts it brings to light:

What can visitors expect from the Discovering Teen Rex live preparation?

The "Discovering Teen Rex" temporary experience offers a unique opportunity to witness scientists actively working on the preparation of the T. rex fossil. Visitors will gain insight into the meticulous process of uncovering and studying fossils, as well as the incredible journey of discovery that led to this finding. The guests will be able to ask the scientists questions and watch as they uncover more bones from this amazing specimen.

The fossil prep lab will be displayed alongside a wide array of dinosaur fossils, including Triceratops and Edmontosaurus, from the Museum’s collection. Experience history in the making as our team of renowned paleontologists clean, preserve and study this rare adolescent T. Rex fossil — one of only a handful found worldwide before your eyes on the Museum floor. “Discovering Teen Rex” is included with general admission.

How Big Was the Teen Rex?

responsive image

Skeletal diagram showing what bones, highlighted in blue, were discovered during the excavation. (Illustration/ Scott Hartman)

The Teen Rex bones found by the kids included parts of the skull, tail, leg and hip. The scientists carefully wrapped all those big bones in a huge plaster jacket about as long as a pickup truck!

responsive image

Our specimen, in blue, was much smaller than most other (Photo/Scott Hartman and Franoys)


The Teen Rex was huge - around 25 feet long and weighed as much as two rhinos! But adult T. rexes were even bigger, around 40 feet long and as heavy as four rhinos. The scientists will keep studying the bones to learn exactly how old the Teen Rex was when it died millions of years ago.

How much did it weigh?

responsive image
Illustrated by Andrey Atuchin

The scientists wrapped up the huge Teen Rex fossil in a giant plaster jacket weighing 6,000 pounds – that's as heavy as a baby elephant! By studying its bones, our Museum scientists estimate the actual Teen Rex dinosaur weighed around 3,500 pounds when it was alive millions of years ago. That's about as much as two rhinos!

Learning the exact weight helps the scientists understand how the T. rex grew from babies into such massively heavy adult dinosaurs.

How Can We Estimate the Teen Rex's Age?

responsive image

Museum scientist Evan Tamez-Galvan uses a 70-pound jackhammer to remove the overlying rock. (Photo/ Natalie Toth)

The scientists used a few different tricks to figure out how old the Teen Rex was when it died. First, they measured the leg bone and compared it to full-grown T. rex leg bones. Since the Teen Rex's was shorter, they could tell it was still growing and just a teenager. They also plan to study the bone up close under a microscope. 

Finding a teenage T. rex is really exciting because most other T. rex fossils are from adults. Studying this Teen Rex lets scientists see what T. rexes were like when they were quickly growing into the massive, fierce dinosaurs we picture. It helps show how they changed from youngsters into ferocious hunters.

Not only is the specimen now on display at the Museum, but the story of this incredible discovery is featured in the recently released film “T.REX,” currently playing in our giant screen Infinity Theater!

Watch the trailer here:

The Museum would like to recognize our exhibition’s presenting sponsor, Chevron. The Museum also acknowledges the generous support of the Genesee Mountain Foundation.

Back To Top