“Trinity” the Tyrannosaurus rex sold at auction last month for $5.3 million.

The T. rex is composed of 293 bones excavated from three sites in Montana and Washington. The bones were dug up between 2008 and 2013 and assembled into a single skeleton, known as a composite. The figure measures 38 feet long and 12.8 feet high, and according to the auction house that sold Trinity, the skull was particularly rare because of how well-preserved it is. Trinity was bought by a European private collector.

Dinosaurs lived during the Mesozoic Era, and the T. rex is one of the most well-known dinosaurs. These famous dinosaurs roamed the Earth between 65 and 67 million years ago, and one study estimates that about

2.5 billion of the dinosaurs lived during their time.

Trinity is the most recent T. rex skeleton auctioned off, but it is not the only one ever sold. Chicago’s Field Museum of Natural History bought Sue for $8.4 million more than 25 years ago and Stan sold for nearly $32 million three years ago. These bones came from the same region in the United States.

The sale of fossils is not without controversy. When fossils are unearthed on private land, they can be sold to private individuals. However, some experts worry that when private citizens buy fossils, they become unavailable for scientific study. It also makes it harder for scientists to work on private land because landowners are incentivized to allow people and companies to dig for fossils who will sell them at auction.

Last year, the skeleton of a Gorgosaurus, a T. rex relative, sold at auction for more than $6 million. It was the first and, so far, only fossil of its kind to ever be offered for private ownership. Two years ago, a triceratops skeleton named Big John sold for $7.2 million to a private collector. Big John holds the world record for the largest triceratops skull ever found—measuring more than 5 feet long!