Rare juvenile T. rex fossil unearthed by 3 boys, now on display at Denver museum

Installation of collection material in the Teen Rex exhibit space. Natalie Toth, Denver Museum of Nature and Science.

A juvenile T. rex fossil is on display at the Denver Museum of Nature & Science, and the public can thank a group of kids for the amazing discovery. 

Museum officials said Kaiden Madsen, then 9, joined his cousins, Liam and Jessin Fisher, then 7 and 10, on a hike through a stretch of land owned by the Bureau of Land Management around Marmarth, North Dakota.

Liam Fisher recalled that he and his dad, who accompanied the trio, first spotted the bone of the young carnivore. After its death around 67 million years ago, it was entombed in the Hell Creek Formation, a popular paleontology playground that spans Montana, Wyoming and the Dakotas. The formation has yielded some of the most well-preserved T. rex fossils ever. 


Tyler kids (Liam Jessin Kaiden) 

Liam said he thought the bone sticking out of the rock was something he described as "chunk-osaurus" — a made-up name for fragments of fossil too small to be identifiable.

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Still, Sam Fisher snapped a picture and shared it with a family friend, Tyler Lyson, the associate curator of vertebrate paleontology at the Denver Museum of Nature & Science.

Initially, Lyson suspected it was a relatively common duckbill dinosaur. But he organized an excavation that began last summer, adding the boys and a sister, Emalynn Fisher, now 14, to the team.


The Denver Museum of Nature & Science

It didn't take long to determine they had found something more special.

Based on the size of the tibia, experts estimate the dino was 13 to 15 years old when it died and likely weighed around 3,500 pounds (1,587.57 kilograms) — about two-thirds of the size of a full-grown adult.

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Ultimately, a Black Hawk helicopter airlifted the plaster-clad mass to a waiting truck to drive it to the Denver museum.

Jessin, a fan of the Jurassic Park movies and an aspiring paleontologist, has continued looking for fossils, finding a turtle shell just a couple days ago.

For other kids, he had this advice: "Just to put down their electronics and go out hiking."

The Associated Press contributed to this report. This story was reported from Los Angeles.