Images of the T. rex fossil nicknamed "Gus" up for auction at Sotheby's in July 2026. The skeleton is about 63% complete by bone count, the most complete ever auctioned. (Image Credit: Sotheby's / Matthew Sherman)

A towering Tyrannosaurus rex that once roamed a warm, swampy world of coastal floodplains and river systems is now headed for the auction block, where it could become one of the most valuable dinosaurs ever sold.

The fossil, nicknamed “Gus,” will headline Sotheby’s Natural History auction in New York on July 14 with an estimated value of $20 million to $30 million. Sotheby’s said it's one of the largest and most complete T. rex fossils ever discovered and the most valuable dinosaur ever offered at auction.

“Gus” dates back roughly 67 million years to the Late Cretaceous, when the climate across what is now western North America was much warmer than today, sea levels were high and broad coastal floodplains supported a rich web of life. Those environments helped sustain large plant-eating dinosaurs such as Triceratops and Edmontosaurus, which in turn supported apex predators like T. rex.

At about 38 feet long and 12.5 feet tall, “Gus," includes 183 fossil bone elements and is about 63% complete by bone count, with those bones representing 75% to 80% of the animal’s bone mass, according to Sotheby’s.

The skull is well preserved, with about 82% of its bones represented, including all six dentitions. Sotheby’s said the fossil also includes a set of humeri, a furcula, or wishbone, two well-represented feet, a complete pelvis and axial skeleton.

The fossil was found in Harding County, South Dakota, on land owned by the late Gary “Gus” Licking, a cattle rancher who had long been interested in the history hidden beneath his land. After years of finding teeth and small bone fragments on the ranch, Licking partnered with Thomas Heitkamp and his team at Theropoda Expeditions to search the property.

Heitkamp’s team discovered the fossil in an area Licking had suggested on the 6,500-acre ranch. Licking died one year into the excavation, before the full specimen was brought to light. The T. rex was named “Gus” in his honor.

The excavation took three summers, followed by another three years of lab work to remove the fossil elements from rock, clean and prepare them, and mount the skeleton.

“The site was a complex fossil bed and preserved alongside many fossils of the flora and fauna that comprised the larger Cretaceous ecosystem,” Heitkamp, president of Theropoda Expeditions, said in a statement.

Heitkamp said the work felt like “tackling the world’s hardest puzzle, except we have to find all the pieces first.”

The fossil also carries signs of a violent life and afterlife. Sotheby’s said “Gus” has pathologies on the skull, vertebrae and appendicular skeleton, including fractured and healed bones in several ribs and gastralia. Bite marks appear on several skull bones and postcranial elements, some possibly from scavenging.

Only a small number of T. rex specimens have ever been discovered, and many are represented by just a single bone. Sotheby’s said only two have been confirmed to be more than 60% complete: “Sue,” housed at the Field Museum in Chicago, and “Stan,” housed at the Natural History Museum Abu Dhabi.

“Gus” will be on public view at Sotheby’s New York galleries at the Breuer from July 1 through July 14. The exhibition is free and open to the public.