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Scientists have described a diminutive new tyrannosaur from New Mexico, US.

Called Suskityrannus hazelae, the dino would have stood about 1m tall at the hip and was perhaps no more than 3m in length - not much longer than just the skull of fearsome T. rex.

"Suski" lived earlier in time, however - 92 million years ago, compared with 80–66 million years ago for the biggest members of the tyrannosaur dynasty.

It should, though, provide some fresh evolutionary insights, researchers say.

"The discovery of Suskityrannus is a rare instance where we find a key new species from a poorly known period of Earth history, and the discovery shows what tyrannosaurs were like before they became the formidable predators like Tyrannosaurus rex that have captured the imaginations of so many people," said Alan Turner from Stony Brook University.

The description of Suski appears in the journal .

Virginia Tech's Sterling Nesbitt, the lead author on the paper, found a number of the key bones as a 16-year-old high school student in 1998, while participating on a dig expedition in New Mexico's Zuni Basin.

Understanding those bones has been a major part of his palaeontology career ever since.

"Suskityrannus gives us a glimpse into the evolution of tyrannosaurs just before they take over the planet," he said.

Co-author Steven Brusatte from the University of Edinburgh, UK, added: "Suskityrannus is a key link between the enormous bone-crunching dinosaurs like T. rex and the smaller species they evolved from.

"The new species shows that tyrannosaurs developed many of their signature features like a muscular skull, broad mouth, and a shock-absorbing foot when they were still small, maybe as adaptations for living in the shadows."