Stegosaurus' Armored Plates Determine the Sex of These Dinosaurs

Scientists may have found the first ever convincing evidence for sex differences in a popular species of dinosaur: the Stegosaurus. Researchers have found that Stegosaurus plates may have different between males and females.

The Stegosaurus was a large, herbivorous dinosaur that lived about 150 million years ago. It had a striking appearance, with two staggered rows of bony plates along its back and spikes at the end of its tail.

Yet these plates differed from animal to animal. Some individuals had wide plates, while others had tall plates. The wide plates were about 45 percent larger overall. Now, though, researchers may have found a reason for these differences: sex.

Sexual dimorphism is common in living animals. This is when the male and female have distinct, anatomical differences. For example, male lions have a mane while female lions don't, and male deer have antlers while female deer don't. That said, sexual dimorphism is extremely difficult to determine in extinct species.

The researchers uncovered a group of dinosaurs in Montana, which demonstrated the coexistence of individuals that only varied in their plates. If the two were different species, then there would have been other differences that would have separated them into ecological niches.

So what does this mean? The best explanation for the differing plates was sexual dimorphism.

"As males typically invest more in their ornamentation, the larger, wide plates likely came from males," said Evan Saitta, one of the researchers, in a news release. "These broad plates would have provided a great display surface to attract mates. The tall plates might have functioned as prickly predator deterrents in females."

The findings reveal a bit more about the Stegosaurus and show how males and females of the species may have differed.

The findings are published in the journal PLOS One.

For more great science stories and general news, please visit our sister site, Headlines and Global News (HNGN).