The mounted skeleton of a newly-identified dinosaur once mistaken for a young Tyrannosaurus rex is up for auction - with a price-tag of at least $6m (£4.5m).
Nicknamed "Jodi", the roughly 10-foot-tall (3m) skeleton will be auctioned by Sotheby's in New York. The sale comes a year after researchers confirmed that the skeleton belongs to a distinct genus.
The Late Cretaceous carnivore is expected to fetch up to $9m when it goes under the hammer on Tuesday. The auction comes after Sotheby's sold a Tyrannosaurus rex, dubbed "Gus", for a record $50.1m (£37.4m) in July.
The sales comes as some in the scientific community debate whether dinosaur remains should be sold privately.
Sotheby's described "Jodi" as an "excellent exhibition-ready" skeleton with about 191 fossil-bone elements and a "beautifully preserved, virtually complete skull".
The auction house added that the Nanotyrannus is "one of only three such skeletons known to science." The specimen is the first to come to market since the existence of the genus was confirmed by US researchers last October, Sotheby's said.
Megan Jenkins, a palaeontologist at the University of Portsmouth, told BBC Radio 4's Today programme on Tuesday that Nanotyrannus "was for a very long time believed to be sort of a teenager of T. rex".
"But it's a lot smaller and its a lot more gracile. So it's very sort-of sleek, slender, [with] blade-like teeth for slicing through meat," Jenkins said.
Tyrannosaurus rex and Nanotyrannus lived alongside one another during the same geological period approximately 67 million years ago.
"Jodi" was initially exhibited as a juvenile T. rex at London's Frieze Masters international art fair in October 2023, before the Nanotyrannus genus was classified.
The skeleton was discovered in the US state of Montana by rancher Jodi Pierson on her land in the Hall Creek Formation, a heavily studied geological site. It was later excavated by commercial palaeontologist Clayton Phipps.
Phipps also discovered the famous "Dueling Dinosaurs" fossil. That specimen, which shows the remains of a Nanotyrannus and Triceratops apparently in combat, was found eight miles (13km) away from "Jodi" in 2006.
The "Dueling Dinosaurs" discovery became crucial to the research published by Lindsay Zanno and James Napoli that classified Nanotyrannus as separate from T. rex. Their paper ended decades of debate over whether the dinosaurs were distinct from one another.
The auction of "Jodi" comes as some scientists warn that auctions could herald a new era in fossil collecting by the ultra-rich.
Researchers told the BBC after the sale of "Gus" that such remains should be exhibited in public spaces where they can be more freely studied.
Prof Steve Brusatte, a palaeontologist at the University of Edinburgh and consultant on the Jurassic Park films, told BBC World Service's What in the World programme in July that the T. rex's auction was "concerning".
"I don't know of any museum or university that can afford a price tag like that," he said. "Imagine if the Mona Lisa was just owned by a super-wealthy person and it wasn't on display and people couldn't see it, couldn't enjoy it."
He said that the time that he hoped such a sale didn't become a trend, adding it could adversely affect scientific research and public education.
Responding to today's auction, Brusatte called it "harrowing" that "Jodi" could disappear from public view.
"We've really just found out that Nanotyrannus is real, and now one of the best skeletons is about to be sold to the highest bidder, and it's harrowing to think it could disappear into the vaults of a collector rather than displayed on a museum where it can wow and inspire kids and families and the public at large," he told the BBC.
But Jenkins told the Today programme on Tuesday there were two sides to the debate, and that a lot of time, effort and money went into excavating the specimens.
"I don't begrudge the people involved for wanting to sell it for such a large amount of money," she said. "Although its a scary prospect, actually a lot of them have ended up in the public eye... these things without a doubt will end end up in a museum at some point."