The skeleton, nicknamed “Stan”, after the amateur paleontologist, Stan Sacrison, who found it in South Dakota in 1987, was sold for more than five times its estimate of $8m.
It is one of the most complete T. rex skeletons ever found, and one of only 50 sets of T. rex fossil remains known.
It was sold at Christie’s Auction house to an anonymous telephone bidder at the auction house’s 20th Century Evening Sale on 6 October.
It was described by James Hyslop, head of Christie’s Science & Natural History department, as “one of the best specimens ever discovered”.
The skeleton is of an adult male T. rex from the famous Hell Creek Formation. This area of rock includes a series of fresh and brackish-water clays, mudstones, and sandstones of mostly Upper Cretaceous and some lower Paleocene rocks and stretches across parts of Montana, North Dakota, South Dakota, and Wyoming.
Other finds from the formation include triceratops, pterosaurs, ankylosaurs, champsosaurs, lizards, frogs and salamanders.
The T. rex skeleton is from the late Cretaceous period (around 67 million years ago).
The skeleton is made up of 188 bones, which have been mounted on a custom frame.
The lot also included a separate display for the original skull, said to be in “pristine condition” and with 11-inch long teeth.
The remains are also notable for evidence indicating the violent life the enormous animal endured, with pathologies such as puncture wounds to the jaws as well as a healed break to the neck vertebra.
After it was found in 1987, it was then excavated by the Black Hills Institute of Geological Research from 14 April to 7 May, 1992. Additional skeletal remains were excavated in 1993 & 2003, according to Christie’s.
Humanity has only known about the existence of the species since the early 20th century after remains were first documented by the paleontologist Barnum “Mr Bones” Brown in 1902.
But the gargantuan carnivore dinosaur swiftly became a subject of global fascination.
T. rex could grow to lengths of over 12m (40 ft), stood up to 3.66m (12 ft) tall at the hips, and weighed up to 14 metric tons.
According to Christie’s, this individual is believed to have died in a small streambed – a factor which allowed the conditions for its bones to be perfectly fossilised.
After death, the creature’s body was disarticulated by the waters of the stream. Some of the bones were carried away, but the majority of the skeleton was then gradually covered with sand, mud and leaves.
Due to the thick layer of leaves found close to the bones, it is believed Stan died sometime in the late summer or early autumn.
“Over time, most of the bone cells were filled with minerals carried by water seeping through the sediments, which then preserved them through time.”
When the skeleton was excavated, each individual bone had to be carefully removed from the host rock, cleaned, preserved, restored and recorded.
Following more than 30,000 hours of manual labour, the bones were then assembled on a custom-built mount.
The towering skeleton – almost 40-feet long – was unveiled as the centerpiece of Japan’s T rex World Expo in Tokyo in 1995.
Following his return from Japan to the USA, the skeleton has been exhibited at the museum of the Black Hills Institute for over two decades.
In 2005 Stan’s skull was modelled and tested to reveal the species had a bite force of four tons per square inch – easily enough to crush a car.