Giant Footprints Reveal Another Hadrosaur Larger Than T-Rex

It's incredible to think how many giant beasts have roamed the land throughout Earth's 4.5 billion years. Today, we certainly have some impressive creatures living alongside us. The Antarctic blue whale is the world's largest animal, weighing up to 400,000 pounds and measuring up to 98 feet long. Though no land mammal can rival this or many other whale species, we do have some land-dwelling giants, too, from the American bison, which is one of the biggest land mammals in the United States, to the actual biggest land mammal in the world, the African bush elephant.

But throughout the long history of the world there have been even more impressive beasts that walked the surface of the earth. The Paraceratherium, a relative of the rhinoceros that lived 34 to 23 million years ago, is thought to have been the largest land mammal ever and is estimated to have reached lengths of 25 feet and weights equivalent to five elephants. When it comes to dinosaurs, several species of sauropods known as Titanosaurs were the largest to ever exist.

Though it couldn't quite match the behemoths that were the Titanosaurs, the Tyrannosaurus Rex was one of the biggest therapods and the largest of the Tyrannosauridae family, which also included Tarbosaurus, Albertosaurus, and Yutyrannus. But in 2024, scientists from Japan and Mongolia uncovered huge dino footprints in the Mongolian desert which look to have belonged to a massive hadrosaur. This giant Saurolophus would not only be one of the largest hadrosaurs to ever exist, it would surpass the size of a T-rex.

Scientists have previously discovered fossils which reveal the Tyrannosaurus rex could reach lengths of up to 40 feet long and heights of up to 12 feet. These mighty creatures are also thought to have weighed as much as 15,500 pounds. But this latest discovery points to a giant hadrosaur that would have been even larger.

Hadrosaurs are known as the "duck-billed dinosaurs" due to the fact their skulls featured wide, flat beaks. They lived from 75 to 65 million years ago in the upper Cretaceous period, and fossils have been found in Europe, Asia, and North America. These herbivores were land-dwellers, and until now, the largest known example was that of Shantungosaurus, a hadrosaur skeleton unearthed in Shandong Province, China.

Now, an investigation into a site in Mongolia, identified back in 2018, has uncovered giant footprints that point to an equally large, if not larger, Saurolophus. Conducted from June 1 to 15, 2024, the dinosaur survey saw a team led by Dr. Shinobu Ishigaki, director of the OUS Museum of Dinosaur Research, explore the previously identified site in Mongolia's western Gobi Desert. A collaboration between Okayama University of Science (OUS) and the Institute of Paleontology, Mongolian Academy of Sciences, the survey uncovered new trackways which included a sequence of 13 fossilized footprints across a distance of 79 feet and three of the largest hadrosaur footprints ever found.

The largest footprint found during Dr. Shinobu Ishigaki's investigation, measuring 3 feet wide, is thought to have belonged to a Saurolophus that would have measured about 50 feet. That means it would have the Tyrannosaurus and fellow giant Tyrannosauridae, Tarbosaurus, beat in terms of sheer size. Not only that, the footprint suggests that this particular beast was one of the largest bipedal animals to ever exist — though at this point no skeletal remains of the dinosaur have been found.

However, Dr. Ishigaki and his team remain hopeful that such a discovery is on the horizon, with the doctor saying in a press release (via Phys.org), "Our next goal is to uncover the full skeleton of the large Saurolophus responsible for these footprints." Even without such a discovery, however, the footprints alone are remarkable. As Dr. Ishigaki pointed out in his remarks, the tracks — which constitute one of the three main types of fossils, i.e. trace fossils — enable "the analysis of posture, walking style, speed, and group behavior," all of which are things skeletal fossils wouldn't reveal.

The other 13 fossilized footprints were also fairly impressive in terms of size, measuring around 2.8 feet in width. All of which bodes well for a bigger skeletal discovery of some sort to come. For now, these Saurolophus footprints are an exciting enough discovery on their own, and a reminder of just how colossal some of our extinct land mammals really were.