Evan Thomas Saitta, University of Bristol MSc student says that you can easily tell the difference between a male and a female Stegosaurus by their two rows of staggered bony plates. Although he believes that males have larger plates and the females have thinner plates, he can’t be sure. Saitta revealed in PLOS ONE, that some Stegosaurus samples he examined had large plates while others had tall plates. These plates were 45% wider overall. Saitta speculated on which one was male and which one was female. The large plates could have been used to display their mates. These plates could have been used as predator deterrents for females.” Here are two hypothetical images of the Stegosaurus male and female. Evan Saitta, Credit: “These stegosaurs appear to be the first convincing evidence of sexual dimorphism within a dinosaur-specific species.” Dimorphism is very common. Anatomical differences among males and women in the same species (dimorphism), are common among animal species today. It is difficult, however, to identify extinct species, particularly dinosaurs, because it can be so hard. Stegosaurus, a dinosaur that ate plants and was about 150 millions years old, is now extinct. Two rows of bony plates ran along the back, in staggered rows. Saitta examined several Stegosaurus Mjosi plates. These specimens were found in Montana’s Stegosaurus “graveyard”. He also examined previously excavated Stegosaurus-mjosi specimens. He discovered that both the tall-plated and wide-plated Stegosaurs were of one species. They were also not individuals of different ages. A) Largest wide morphplate. B) The tallest morph plate. Image: PLOS One. CT scanning and microscope analysis revealed that both types of plates had stopped growing. Therefore, the differences in the plates could not be due to different ages. Saitta stated that researchers may be able to see more detail about Stegosaurus behavior if they can find evidence of sexual dimorphism among extinct species. Saitta wrote in an abstract in the journal that “Dinosaur ornithology may have served the same functions as modern species’ ornamentation.” Comparing extant ornamentation, like the horns and bovids, to predict the role of dinosaur ornamentation may prove useful. Citation: Evan Thomas Saitta. “Evidence of Sexual Dimorphism In the Plated Dinosaur Stegosaurus Mjosi (Ornithischia Stegosauria), from the Morrison Formation (Upper Jurassic), of Western USA.” PLOS ONE. 22 April. 2015. DOI: 10.1371/journal.pone.0123503. BBC Video – Stegosaurus This BBC video shows how Stegosaurus might have protected itself from predators using its spiked tail.
The bony plates on Stegosaurus’ backs are what distinguish them from each other
