A new study has revealed that stegosaurus males and females can be identified through the size of the bony plates along their backs.
The discovery, by Princeton University, of a single anatomical difference between males and females of a species of Stegosaurus provides some of the most conclusive evidence that some dinosaurs looked different based on sex, according to new research.
It was found that the back plates of the species Stegosaurus mjosi came in two varieties that indicated the animal's sex; short and wide, and tall and narrow. Females had one type of plate and males donned the other. The lack of a particular female-specific bone tissue found in birds and some dinosaurs, however, made it difficult to determine which sex had which plate type.
Beyond the implications for Stegosaurus, the research established that sexual dimorphism, in which males and females of a species have distinct physical forms, could exist in non-avian dinosaurs, which includes iconic reptiles such as Tyrannosaurus and Brontosaurus.
Existing work on sexual dimorphism in non-avian dinosaurs had been inconclusive to the point that some paleontologists began to think that male and female dinosaurs did not differ physically from one another.
Author Evan Saitta plans to follow up with his research by exploring the possible result of sexual dimorphism in S. mjosi on biology, such as how a trait evolved in response to a species' risk of predation or ability to attract mates.
The study is published in the journal PLoS ONE.