Sexing Dinosaurs: How Do You Do It?

When it comes to living creatures being able to distinguish a boy from a girl is vital. In living creatures this task is so simple that many consider it to be mundane. How you sex a specific creature will vary based on what species it is, but we all know how to go about doing it. For mammals sexing is often done with reproductive parts, while with birds it is based on the color of the feathers, and with some reptiles sex is determined based on eye color.

So knowing how to tell living creatures apart based on sex is something that most of us can easily do, but that leaves the question of how to sex animals that are now extinct, such as the dinosaurs. If you have watched any dinosaur movie, yes even the famous Jurassic Park series of movies, you will notice that all of the dinosaurs look alike. There really is no difference between one T-Rex and the other, but based on the fact that they had babies you know one was male and one was female. So that leads us to the question of how to tell the boys from the girls.

One problem that scientists have run up against is the fact that the dinosaurs no longer roam the Earth. All scientists have to work with is the various fossils found throughout the world, sometimes they are intact, but more often they are not. And trying to tell a male dinosaur from a female dinosaur based on their skeleton is no easy feat. In fact, most species of dinosaurs it is an impossible feat.

However, based on a study that was released Wednesday, April 22, 2015, scientists may now be able to tell the difference between boys and girls in the popular Stegosaurus. The study shows that to tell the difference between boys and girls you must use the bony plates that are found along the back of the animal.

Using fossils from several individual Stegosaurs found in the Stegosaurus “graveyard” in Montana, scientists noticed the something interesting about the plates. The plates along the backs of these animals came in two separate and distinct groups, wide or tall. The wide plates had a 45% larger surface area than the taller ones did, while the tall ones reached about 3 feet tall.

Using age old information about how males from various species are more attractive to look at, think the mallard duck for a great example, scientists determined that the wider plates belonged to the males, while the taller ones belonged to the female. According to Evan Saitta, who helped with the study, if you look at the placement of the plates along the males back it is highly suggested that they were used in a sexual display, similar to a tail of a peacock.

Now many people might put the difference in plates off to the fact that the dinosaurs were different ages, some might have been older, while others were younger. Keeping this in mind researchers conducted a microscopic analysis, as well as a CT scan from each specimen. What the results showed was that in all of the specimens bone tissue had quit growing, which meant they were all full-sized adults.