A T. rex named Stan just became the most expensive dinosaur ever sold. The 40-foot-long skeleton went for $31.8 million.

• A 67-million-year-old Tyrannosaurus rex skeleton named Stan sold for $31.8 million at Christie’s auction house in New York City on Tuesday, making it the most expensive dinosaur skeleton ever sold. 
• An anonymous buyer won the auction after 20 minutes of bidding.
• Only 50 or so T. rex skeletons have ever been found. Only one-quarter of them, including Stan, are considered complete skeletons.
• Stan died 67 million years ago, and would’ve stood 13 feet tall and 40 feet long when alive. 
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T. rex skeletons are highly coveted.

There have been 50 or so specimens discovered in the last 115 years, but only one-quarter of those are complete — meaning more than half the skeleton’s bones were dug out of the earth. 

So when Christie’s, an auction house in New York City, announced last month it would be selling a complete T. rex named Stan, it generated quite a stir.  

At its “20th Century Evening Sale” on Tuesday, Christie’s sold Stan for a whopping $31.8 million, making the T. rex the most expensive dinosaur skeleton ever sold.

That’s nearly four times more money than the auction house expected to get when it put the skeleton up for display at 20 Rockefeller Center in September.

The fate of a 67-million-year old fossil 

More than a quarter of a million online viewers tuned in to find out Stan's fate on Tuesday.

After a 20-minute bidding war, an anonymous buyer snapped up the skeleton over a London phone call with James Hyslop, head of Christie's science and natural history department, according to the New York Times.

The last time a complete T. rex got auctioned was in 1997, when the Field Museum of Natural History in Chicago bought a skeleton named Sue for $8.36 million. So it's unsurprising that Stan was in high demand.

Stan would've stood 13 feet tall and 40 feet long in life and weighed nearly 8 tons. The T. rex's serrated teeth are 11 inches long; some of the skeletal features suggests Stan was male. 

It's "one of the best specimens ever discovered," Hyslop said in an article on Christie's website.

Paleontologist Stan Sacrison found the fossil in South Dakota's Hell Creek Formation in 1987. In the years prior to the auction, researchers studied the skeleton at the Black Hills Institute of Geological Research. They determined Stan was 67 million years old. 

Stan lived with a broken neck 

Besides being one of the largest, most complete T. rexes ever found, Stan is unique because his skull is wholly intact and well-preserved.

Puncture wounds on Stan's skull, cheeks, and lower jaw suggest he was bitten when fighting other T. rexes.

Two of Stan's neck vertebrae are fused together near a T. rex tooth-shaped hole, revealing he had healed from a bite to the back of the head.

"Stan also suffered a broken neck," paleontologists from the Black Hills Institute wrote, adding, "apparently, his spinal cord was not severed, or he would not have lived to heal."