Largest Tyrannosaurus rex specimen

Measuring approximately 4 metres (13 feet) tall and 12.5 metres (41 feet) long – based on skeletal remains that are around 90% complete – "Sue" is widely considered to be the largest example of a T. rex found to date. The skeleton – the most intact and well-preserved T. rex on record – was excavated in the Hell Creek Formation in South Dakota, USA, on 12 August 1990. It was found by explorer and fossil collector Sue Hendrickson (USA), after whom the dinosaur was named.

Another contender for the title is "Scotty" (or RSM P2523.8), which was discovered in the Frenchman Formation near Eastend in Saskatchewan, Canada, on 16 August 1991 by the then high-school teacher Robert Gebhardt (Canada). A study published in The Anatomical Record in April 2019 assessed the dimensions of the approximately 65% complete dinosaur and determined its body mass (based on femur measurements) to be in the region of 8,870 kilograms (19,555 pounds) – which would make Scotty more massive than Sue. The study's lead author, Dr W Scott Persons, estimates that Scotty stood around the same height as Sue, but was slightly longer at 13 metres (42 feet 7 inches) from head to tail tip.

Owing to incomplete skeletons and the unavoidable element of educated extrapolations when it comes to calculating dinosaur size, it's too close to call whether Sue or Scotty was definitively larger.

As well as being superlatively large examples of their kind, both Sue and Scotty are among the oldest T. rex discovered to date, estimated to be around 28 years old, or perhaps 30-plus years old in Scotty's case. Both skeletons show the scars of many battles with other dinosaurs during their lives.

Sue is on display at The Field Museum in Chicago, Illinois, USA. A skeleton cast of Scotty is displayed at the Royal Saskatchewan Museum's T. rex Discovery Centre in Eastend, with another cast due to go on display at the Royal Saskatchewan Museum in Regina, Canada, in May 2019.