A short-necked relative of today’s giraffe was likely the most massive cud-chewing mammal ever to stroll Earth, a new study suggests. Few fossils of Sivatherium giganteum, a species first described in 1836, have been unearthed. Paleontologists originally thought the creature, which lived in the Himalayan foothills about 2.6 million years ago, was an elephant-sized cousin to both modern-day cud-chewers such as sheep, goats, cattle, and giraffes (scientifically known as ruminants), and living behemoths such as elephants and rhinos. A modern analysis, however, trims the beast’s heft considerably. First, researchers made a computer model of S. giganteum’s known bones or mirror images of them (tan, in image above), changing their scale, when necessary, to make them fit well at the joints. Then, they added a scaled-up version of the bones from a modern-day giraffe’s torso and pelvis (gray); as it turns out, all known extinct relatives of today’s giraffids (giraffes and okapi) have similarly shaped bodies. Finally, after fleshing out the bones and measuring the creature’s volume, the team estimates that S. giganteum tipped the scales just shy of 1250 kilograms. That’s slightly less than one-fifth the weight of a large African elephant, but about 5% more than an average male giraffe, the largest living ruminants, the researchers report online today in Biology Letters. The team’s new weight estimate for S. giganteum doesn’t include the weight of the large, antlerlike appendages on the head, which possibly were sported only by males, the researchers note. Nor does it include the possibility of larger individuals of the species; one of the leg bones used in the team’s model had to be shrunk about 15% to get it to fit well with its neighboring bones from other creatures, which suggests that considerably larger and heftier S. giganteum existed.
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