|Stegosaurus is amongst the most iconic of the dinosaurs|
They may have acted as solar panels, allowing the sun to heat the blood within a dense network of vessels. In turn, their spiked tails were a perfect means of defence against their carnivorous cousins, the theropods. All in all it is a well known and studied species, yet the familiar can still yield surprises. A recent study has shown that the shape of a Stegosaurus's plates relates to gender.
Sexual dimorphism is the technical term for members of the same species, but different genders, possessing different morphologies. Female angler-fish are much larger than males, male birds-of-paradise have resplendent plumages whilst females have not. Identifying sexual dimorphism in fossils is more difficult due to its potential confusion with the morphological differences between juvenile and adult, as well as male/female. Having spent six summers in central Montana, as part of an excavation crew, Evan Saitta from the University of Bristol was able to identify conclusively sexual dimorphism in the species Stegosaurus mjosi.
|The plates in Stegosaurus mjosi give an indication as to |
the gender of the individual from which they come.
'Males typically invest more in their ornamentation,' said Saitta. '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 identification of sexual dimorphism in Stegosaurus is an important step forward as it gives us an indication as to how we may identify the trait in other dinosaur species. In turn, an understanding of gender balance in dinosaur populations will impact on how we model Mesozoic ecosystems and the ecological interactions which comprised them.