Science, Tech, Math › Animals & Nature Facts About Argentinosaurus, the World's Biggest Dinosaur Share Flipboard Email Print Warpaintcobra / iStock / Getty Images Plus Animals & Nature Dinosaurs Herbivores Basics Paleontologists Carnivores Dinosaurs & Birds Marine Reptiles Prehistoric Mammals Amphibians Birds Habitat Profiles Mammals Reptiles Wildlife Conservation Insects Marine Life Forestry Evolution View More By Bob Strauss Science Writer B.S., Cornell University Bob Strauss is a science writer and the author of several books, including "The Big Book of What, How and Why" and "A Field Guide to the Dinosaurs of North America." our editorial process Bob Strauss Updated August 19, 2019 When it was discovered in Argentina in 1987, Argentinosaurus, the world's biggest dinosaur, shook the world of paleontology to its foundations. Ever since its discovery, paleontologists have argued about the length and weight of Argentinosaurus. Some reconstructions put this dinosaur at 75 to 85 feet from head to tail and up to 75 tons, while others are less restrained, positing (somewhat less credibly) a total length of 100 feet and a weight of a whopping 100 tons. If the latter estimates hold, that would make Argentinosarus the biggest dinosaur on record based on well-attested fossil evidence. 01 of 09 Argentinosaurus Was a Type of Dinosaur Known as a Titanosaur Given its gigantic size, it's appropriate that Argentinosaurus is classified as a titanosaur, the family of lightly-armored sauropods which spread to every continent on Earth later in the Cretaceous period. This dinosaur's closest titanosaur relative appears to have been the much smaller Saltasaurus, clocking in at a mere 10 tons and living a few million years later. 02 of 09 Argentinosaurus May Have Been Preyed Upon by Giganotosaurus The scattered remains of Argentinosaurus are associated with those of the 10-ton carnivore Giganotosaurus, meaning these two dinosaurs shared the same territory in middle Cretaceous South America. While there's no way even a desperately hungry Giganotosaurus could have taken down a full-grown Argentinosaurus all by itself, it's possible that these large theropods hunted in packs, thus leveling the odds. 03 of 09 The Top Speed of Argentinosaurus Was Five Miles Per Hour Given its enormous size, it would be surprising if Argentinosaurus could move much faster than a slowly taxiing 747 jet airplane. According to one analysis, this dinosaur ambled along at a top speed of five miles per hour, presumably inflicting plenty of collateral damage along the way. If Argentinosaurus congregated in herds, as seems likely, even a slow-moving stampede triggered by a hungry Giganotosaurus could have wiped the average watering hole completely off the Mesozoic map. 04 of 09 Argentinosaurus Lived in Middle Cretaceous South America When most people think of giant dinosaurs, they picture behemoths like Apatosaurus, Brachiosaurus, and Diplodocus, which lived in late Jurassic North America. What makes Argentinosaurus slightly unusual is that it lived at least 50 million years after these more familiar sauropods, in a place (South America) the breadth of whose dinosaur diversity is still unappreciated by the general public. 05 of 09 Argentinosaurus Eggs (Probably) Measured a Full Foot in Diameter As a result of physical and biological constraints, there's an upper limit to how large any given dinosaur egg can be. Considering its huge size, Argentinosaurus probably brushed up against that limit. Based on comparisons with the eggs of other titanosaurs (such as the eponymous genus Titanosaurus), it seems likely that Argentinosaurus eggs measured about a foot in diameter, and that females laid up to 10 or 15 eggs at a time — increasing the odds that at least one hatchling would evade predators and survive into adulthood. 06 of 09 It Took Up to 40 Years for Argentinosaurus to Attain its Maximum Size There's still a lot we don't know about the growth rates of plant-eating dinosaurs like sauropods and titanosaurs; most likely, juveniles reached maturity at a much slower pace than that of warm-blooded tyrannosaurs and raptors. Given the ultimate heft of Argentinosaurus, it's not inconceivable that a newborn hatchling took three or four decades to reach its full adult size; that would represent (depending on the model you use) about a 25,000 percent increase in bulk from hatchling to herd alpha. 07 of 09 Paleontologists Have Yet to Find a Complete Argentinosaurus Skeleton One of the frustrating things about titanosaurs, in general, is the fragmentary nature of their fossil remains. It's extremely rare to find a complete, articulated skeleton, and even then the skull is usually missing since the skulls of titanosaurs were easily detached from their necks after death. However, Argentinosaurus is better-attested than most members of its breed. This dinosaur was "diagnosed" based on a dozen or so vertebrae, a few ribs, and a five-foot-long femur thigh bone with a circumference of a whopping four feet. 08 of 09 No One Knows How Argentinosaurus Held its Neck Did Argentinosaurus hold its neck vertically, the better to nibble the leaves of tall trees, or did it forage in a more horizontal posture? The answer to this question is still a mystery — not only for Argentinosaurus but for pretty much all long-necked sauropods and titanosaurs. The issue is that a vertical posture would have placed enormous demands on this hundred-ton herbivore's heart (imagine having to pump blood 40 feet into the air, 50 or 60 times per minute!), given our current state of knowledge about Argentinosaurus' physiology. 09 of 09 Plenty of Dinosaurs Are Vying for Argentinosaurus' Size Title Depending on who is doing the reconstructions and how they evaluate the fossil evidence, there are plenty of pretenders out there for Argentinosaurus' "World's Biggest Dinosaur" title; not surprisingly, all of them are titanosaurs. The three leading contenders are the tongue-twistingly named Bruhathkayosaurus from India and Futalognkosaurus, as well as a more recently discovered contender, Dreadnoughtus, which generated major newspaper headlines in 2014 but which may not have been as big as first advertised.