The Biggest Dinosaurs to Walk The Earth

A cast of Scotty, the largest T-Rex yet discovered. (image credit: Amanda Kelley)
Post Author - Peter Bashaw
For 165 million years across the Mesozoic Era, dinosaurs reached incredible, towering sizes, but curiously the evidence suggests the largest came at the end of the Age of Dinosaurs. This may seem ironic. After all, larger animals have smaller populations and require more food, thus making them susceptible to environmental stresses. On the flip side, if a large animal is able to survive a mass die-off, their genetic predisposition to a large size will quickly spread in a reduced population. This is what we see in the Late Cretaceous: dinosaurs of many different clades reaching their apex.
Among the already massive sauropods, Argentinosaurus was a cut above, weighing around 73 tonnes with a length of around 120 feet, the largest confirmed land animal across the entire fossil record. The largest ornithischian was the Shauntongosaurus, with a length of 50 feet, capable of holding its massive bulk on just its two rear legs. As for the mighty theropods, they reached their peak with the iconic Tyrannosaurus, the largest specimen being a T-Rex named Scotty, measuring 43 feet long and weighing around nine tonnes. Don’t let those stubby arms fool you, Tyrannosaurus was the largest completely bipedal dinosaur in the whole fossil record!
A large size isn’t everything, of course. When the K/Pg extinction arrived, it was the small, mobile dinosaurs that were able to survive while the giants died out. Today, birds have a vast size range, from the nine-foot-tall common ostrich to the bee hummingbird, which measures under two and a half inches in length. One wonders if dinosaurs would have continued to balloon in size had their extinction not come, but for the time being today’s dinosaurs seem satisfied taking on what size their environment calls for.
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