The fossil market is poised for another record when the Tyrannosaurus rex skeleton known as ‘Gus’ goes under the hammer at Sotheby’s in New York on 14 July. Discovered on a private ranch in South Dakota, the 67-million-year-old specimen is one of the most complete ever found, measuring nearly 12 metres from snout to tail. The auction house expects bidding to reach between $20 million and $30 million, which would surpass the $31.8 million paid for a T. rex named Stan in 2020. Two years ago, a stegosaurus sold for $44.6 million, obliterating its pre-sale estimate and highlighting the frothy demand for dinosaur remains among wealthy private collectors.

Against this commercial backdrop, palaeontologists continue to unravel the biology of the Cretaceous apex predator. A team at University College London has offered a fresh hypothesis for one of the most enduring mysteries of T. rex anatomy: its absurdly small arms. The creature could reach 13 metres in length, yet its forelimbs were just one metre long—‘ridiculously small’, according to Charlie Roger Scherer, the doctoral researcher who led the study. While some scholars have suggested the arms were vestigial or used to grip mates, the UCL work argues they were robust and capable of slashing prey at close quarters, perhaps reducing the risk of injury from the dinosaur’s bone-crushing jaws. The research, drawing on biomechanics and comparisons with living relatives, concludes the arms shrank not from disuse but because they were honed for a specific, lethal function.

A separate discovery on the other side of the globe adds texture to the behavioural picture of theropods. In Hebei province, northern China, researchers have mapped one of the country’s largest trackway sites, containing more than 5,000 fossilised footprints. Among the most striking finds is a trail left by a carnivorous dinosaur moving at just one kilometre per hour—the slowest recorded speed for a theropod in such deposits. The strolling pace, documented across a 30,000-square-metre exposure, suggests these predators could shift from lethargic ambulation to explosive pursuit, a duality that fits with the image of a patient, energy-efficient stalker.

Viewed from London, the UCL study underscores the stubborn appeal of T. rex as a subject of serious science, not just Hollywood spectacle. Yet from New York, the Sotheby’s sale raises uncomfortable questions about the privatisation of natural heritage. Institutions in the global South, in particular, struggle to compete with private buyers, echoing debates over colonial-era acquisitions. As the gavel falls in July, Gus will almost certainly disappear into a private collection, a fate that worries researchers who see each skeleton as an irreplaceable archive of prehistory. That the same week brought a deeper understanding of why T. rex arms were short only heightens the sense of what might be lost when specimens vanish from public view.