The extinct, giant giraffid Sivatherium giganteum: skeletal reconstruction and body mass estimation

An extinct giraffe relative was enormous, but not elephant-sized. Sivatherium giganteum had a relatively short neck, thick limbs and elaborate bony headgear. Its unusual bulk had encouraged comparisons with African elephants, yet that impression had never been tested through a detailed reconstruction of its body.

Christopher Basu, Peter Falkingham and John Hutchinson photographed 26 fossil bones held in London's Natural History Museum and assembled digital models into a three-dimensional skeleton. The fossils represented at least three mature individuals. Missing parts, including much of the torso, were reconstructed using a living giraffe's anatomy. The team then estimated body volume, converted that volume into mass and tested how changing uncertain body dimensions affected the answer.

Their preferred estimate was about 1.25 tonnes, with a prediction interval of roughly 0.86–1.81 tonnes: a very large giraffe relative, but not an elephant-sized animal. An estimate based only on upper-arm bone thickness was more than twice as high, suggesting unusually robust forelimbs. The authors proposed that heavy headgear might help explain that build, without demonstrating the connection. The reconstruction also omitted large male headgear and some larger fossils, so it is not a species maximum. Rebuilding the whole animal made its apparent size more credible—and more explicitly uncertain.