Bone by bone and study by study, palaeontologists are learning more than ever before about dinosaurs. But there are still many aspects of prehistoric biology that we know little about. In fact, some of the simplest facets of dinosaur lives remain elusive, like how they slept.

A handful of fossils have shown us that at least some dinosaurs curled up just like birds.

Many articulated dinosaur skeletons are found in the classic dinosaur death pose, with their tails tilted up and their necks thrown over their backs.

Another Mei specimen has confirmed that the first find was not a fluke. Palaeontologists have described a second, slightly smaller Mei that was preserved in a nearly identical sleeping position. Much like the first, this Mei probably died in a prehistoric ashfall that b...