Jose Antonio Penas/Science Photo Library

The ostrich-like Pelecanimimus dinosaur lived around 120 million years ago, during the Cretaceous period, and was 2 metres from head to tail.

Historically, scientists have sidestepped the issue of dinosaur sex, both because there was a bit of a taboo around studying it and there wasn't much evidence. Sadly, no fossils have (yet) been found of dinosaurs actually having sex, and even the best preserved fossils don't show the dinosaur's reproductive system. But by looking to dinosaurs' closest living relatives – birds and crocodiles – scientists are piecing together how they reproduced.

This artist's impressions show what mating dinosaurs might have looked like, based on the little evidence that does exist (with a bit of artistic license thrown in).