A prehistoric giraffe that died out 10,000 years ago might have been the largest ruminant that walked the Earth.
Victorian scientists believed the creature was a giraffe with a trunk and a "missing link" between mammals.
Digital reconstructions of the bones show that while the giraffe was gigantic, the theory that it was as big as an elephant was not true.
The findings, published in Biology Letters, shed new light on the work of 19th Century fossil hunters.
The first fossil specimen was found by the Scottish geologist Hugh Falconer and the English engineer Proby Thomas Cautley on an expedition to the Siwalik hills in India in the 1830s.
In a paper published in 1836, the two men outlined their discovery of an animal with a skull the size of an elephant which they believed had a trunk.
Palaeontologists envisaged it as an elephant sized, moose-like creature - a view that has prevailed.
Christopher Basu of the Royal Veterinary College in Hertfordshire, co-researcher of the study, said the fossil hunters did a "beautiful job at describing it and taking measurements", although it turns out the body mass calculation was "educated guesswork".
Sivatherium was a giant relative of modern giraffes, living over one million years ago in both Africa and Asia.
Unlike the giraffes of today, Sivatherium had a short neck, with short, stocky legs.
At the time of the first discovery of bones of the mammal in the 1800s it was thought to be a link between giraffes and elephants.
"They thought it was this missing link animal," Mr Basu, a veterinary scientist, told BBC News. "They had never seen anything that size with that kind of anatomy."
As part of research into the anatomy of living giraffes, he used modern computer methods to investigate the skeleton of the giraffe "cousin".
By reconstructing the animal's anatomy in 3D, he was able to estimate its body mass.
"As a palaeontologist, it is really important to understand the basic question - how big was this animal?" he explained.
The research - carried out with Liverpool John Moores University - came up with an estimated body mass of 1,246kg (857 to 1,812kg range).
This is thought to be an underestimate, as it does not take into account large horns possessed by the males.
Although its size does not approach that of an African elephant, the animal - dubbed "Siva's beast" - was certainly a large member of the giraffe family and may have been the largest ruminant mammal that has ever lived.
"This was probably the largest giraffe relative to have ever existed, which makes it the largest ruminant that's ever existed," said Mr Basu, who is studying for a PhD.
Such a large ruminant might have struggled to eat enough to provide the energy needed to power such a large body, he added.
"It's a rare animal," he said. "It's pushing the limits of its anatomy."
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