The Triceratops Debate Most People Haven't Heard Of

As more and more discoveries about dinosaurs are made, our understanding of how these ancient creatures looked and behaved changes — often quite dramatically. One of the most obviously significant findings of the last few decades is the fact that many dinosaurs had feathers and were in fact direct ancestors of birds. It's why the truth about what velociraptors really looked like might shock many who grew up with the popular concept of dinos as scaly, reptilian beasts.

But we've also learned so much more about dinosaurs in recent years. For one thing, we now know T. rex sounded a heck of a lot more terrifying than we previously thought, and in 2024, scientists discovered giant footprints that revealed a hadrosaur larger than the T. rex. For the most part, these discoveries don't necessarily penetrate the wider culture, at least not in the way the discovery of dinosaur feathers has of late. But there's a dino debate that's flown even more under the radar than the discovery of T. rex's ominous growl.

Most of us have a conception of what the Triceratops looked like and might not even be aware that, for decades, experts have been arguing back and forth about how Triceratops stood and moved. But this has actually been a surprisingly intense debate. To be more specific, paleontologists have long argued over whether Triceratops had forelimbs that extended straight down below them, like a rhino, or whether they had elbows that stuck out to the side, like a lizard. That might sound surprising as the dinosaur is mostly depicted as standing much like a rhino, but it seems for the longest time Triceratops fossils had not provided an unequivocal answer to this debate.

Part of the problem with understanding how dinosaurs stood and moved is down to the fact fossils only tell part of the story. Soft tissues and the nervous system are also extremely important elements in this puzzle, which has posed a problem for paleontologists working mostly with just fossilized bones. Likewise, preserved footprints have failed to provide conclusive proof as to how Triceratops stood and moved, all of which prompted Dr. Shin-ichi Fujiwara of the University of Tokyo and Professor John Hutchinson from the Royal Veterinary College to try to provide more concrete answers. Their work was published in Proceedings of the Royal Society B back in 2012 and provided compelling evidence that Triceratops did indeed stand more like a mammal than a lizard. 

The researchers developed a method for determining the postures of animals by measuring the elbow bones of 318 species. Fujiwara spent weeks traveling to museums around the United Kingdom and Japan, measuring animal skeletons to create a database against which he and Hutchinson could test their hypotheses. The pair were able to identify the degree of elbow joint mobility in multiple tetrapods — animals with four feet — all of which descend from the last common ancestor of amphibians, reptiles, and mammals. Specifically, they found that the carpal flexor (forearm) muscles played a role as elbow adductors in sprawling animal types, such as lizards of frogs, helping to keep their elbows close to their bodies and prevent them splaying out too far.

Upright animals, however, relied more on elbow extensors and flexors, i.e. their triceps muscles, than the carpal flexor muscles. These creatures, which include dogs, cats, rhinos, and others, were found to have a larger olecranon — the part of the elbow joint where the triceps muscles attach — allowing for more effective leverage over those muscles. 

Based on their findings from measuring and studying modern animal specimens and their skeletal structures, Fujiwara and Hutchinson were able to classify the forelimb postures of extinct tetrapods, including the Triceratops, and found that these extinct creatures had forelimbs that resembled those of upright creatures included in the database. This essentially provided convincing evidence that Triceratops did indeed stand in a more upright position, like rhinos, rather than having their limbs spread out to the sides like a lizard. The findings also suggested the dinosaur could have been more athletic than previously guessed.

As Hutchinson told Phys.org, these findings were particularly compelling because they are based on "statistically rigorous and numerical" data gathered over several weeks from real-life specimens. That said, the study was not conclusive proof that Triceratops had a more mammalian posture, with Hutchinson explaining to Smithsonian Magazine that other evidence might point towards a semi-erect, more sprawling posture. Still, the study was a major step forward in solving this ongoing debate, and today it is indeed widely thought that the creatures stood more upright rather than sprawling. As with so many other aspects of dinosaurs, however, things could change as more discoveries are made.