The skeleton, found on private land in Montana in 2013 by Alan Detrich, was on display at the University of Kansas Natural History Museum until Dietrich made the surprise decision to put it up for sale, according to the Guardian.
The ad reads: "Most Likely the Only BABY T-Rex in the World! It has a 15-foot-long body and a 21" skull with serrated teeth! This rex was very a very dangerous meat eater. It's a RARE opportunity indeed to ever see a baby REX, if they did not grow quickly they could not catch prey and would die. Histology shows the specimen to be approximately 4 years old upon death."