Torosaurus

The Largest Head of Any Land Animal in History and a Unique Frill

Torosaurus’s biggest impact lies in its gigantic head.
Its skull reached a length of 2.7m, making it the largest ever discovered for a land animal.
This massive head, which occupied nearly 40% of its body length, had a total of three horns: one above the nose and two above the eyes.
In particular, its frill was one of the largest among its relatives, with the distance from the tip of its snout to the end of the frill reaching nearly 3 meters.

The frill was more than half the length of its entire skull, but it had two large, eye-like holes, making it lighter than it looked.
These holes are believed to have existed to reduce the weight of the enormous frill, a feature also found in Chasmosaurus and other species.
It is unknown why it was so important to have such a large face, but for ceratopsians like Torosaurus, a large head may have been an absolute requirement for attracting mates.

These huge frills and horns were not just for show; there is vivid evidence that they were used in fierce battles for territory and mates.
Many Torosaurus frills have been found with healed wounds that appear to have been caused by the horns of other individuals.

The “Torosaurus = Triceratops Theory”: A Decades-Long Debate and Its Resolution

The biggest scientific controversy surrounding Torosaurus was the “conspecific theory”: “Was Torosaurus actually a very old Triceratops?”
This theory arose because the two lived in roughly the same time and place and had almost no differences other than the holes in the frill.
Had this theory been accepted, the existence of Torosaurus as a distinct species would have been erased.

In 2010, the renowned paleontologist Dr. Jack Horner and his colleagues published this theory, which garnered a lot of attention.
They noted that only large, mature Torosaurus fossils had been found, and that Triceratops frills showed thin areas that were a precursor to holes opening up with age. They published the groundbreaking theory that “Triceratops would have developed holes in its frill in the final stages of growth, transforming into Torosaurus.”

However, this theory was not accepted by many scientists from the beginning.
Subsequent research provided multiple strong counterarguments, bringing a resolution to the debate.

A Young Torosaurus and an Old Triceratops

Fossils of a young (sub-adult) Torosaurus were discovered, which contradicted the theory. Furthermore, a fossil of a Triceratops that was clearly old based on its bone structure but had no holes in its frill was also found.

Differences in Frill Bone Structure

It was pointed out that the bone structure around the holes in the Torosaurus frill was complex, showing signs of repeated absorption and regrowth, whereas the frill of Triceratops showed no such structure.

Differences in the Number of Small Bones on the Frill’s Edge

The number of small bony projections (epoccipitals) that adorned the edge of the frill was distinctly different between the two.

Based on this evidence, the current scientific consensus is that while Torosaurus and Triceratops are closely related, they are distinct and separate genera.

A Unique Defense System and Fossil Rarity

The head and body of Torosaurus appear lighter than the robust build of Triceratops.
However, as a herbivore, it would have been a target for large carnivorous dinosaurs. But with its large horns and sturdy body, an attack would not have been easy.
In particular, its hip bones were fused and strengthened to protect its back, which was a vulnerable area.
Also, the frill of Torosaurus had long, curving squamosal bones that extended beyond the frill’s surface, which visually distinguishes it from Triceratops.

While Triceratops existed in large numbers, Torosaurus fossils are extremely rare. For every 15 Triceratops skulls found, only one Torosaurus skull is discovered.

Research will undoubtedly continue to reveal more secrets about this giant-headed dinosaur.