One of the most complete Tyrannosaurus rex skeletons in the world is headed for the auction block in New York and is expected to sell for between $6 million and $8 million.

Auction house Christies said the T. rex skeleton, dubbed "Stan" in honor of Stan Sacrison, the amateur paleontologist who found the bones in 1987, will be auctioned Oct. 6 as part of the 20th Century Evening Sale.

The assembled Stan measures 13 feet high, 40 feet long and is composed of 188 bones, making it one of the most complete skeletons of the species in the world.

Researchers at the Black Hills Institute of Geological Research in South Dakota, where Stan was studied for two decades, said the bones reveal the dinosaur suffered a broken neck during its life, causing two vertebrae to fuse together. The T. rex also suffered puncture wounds to its skull and a rib from an apparent encounter with a rival T. rex.

Stan is currently on display 24 hours a day in the windows at Christie's Rockefeller Center in New York.

James Hyslop, head of Christie's Science & Natural History department, said the auction marks "a once in a generation chance."

"There simply aren't T. rexes like this coming to market. It's an incredibly rare event when a great one is found," he said.