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Fossil Evidence

Pterosaurs were flying reptiles that lived more than 66 million years ago. They lived alongside the dinosaurs ― but don’t make the mistake of calling them dinosaurs! They were quite different animals.

Until the discovery of these eggs, only 11 had ever been discovered, which meant that palaeontologists (scientists who study fossils) didn’t know much about young pterosaurs. Now, with 215 more eggs to study, they think they can figure out a lot more about these prehistoric animals!

The scientists think sudden floods during a bad storm swept hundreds of eggs downstream, bumping them into one another and over rocks and stones. When the eggs eventually came to a stop, they were buried in sediment (very fine pieces of rock) very quickly. This sediment also filled the inside of the eggs, coming in through cracks in the shells that were caused by their bumpy journey downriver. Over thousands of years, this sediment caused the eggs and their contents to harden into fossils. They then sat trapped in rock for millions of years, until the group of palaeontologists uncovered them.

Sixteen of the fossils were in such good condition that scientists could even see embryos (developing babies that hadn’t hatched yet) in them. These embryos were at different stages of development, so some were closer to hatching age than others. This allowed scientists to see snapshots of how baby pterosaurs formed within the egg, which helped them create a development timeline.

One of the most interesting discoveries they made was that pterosaurs’ back legs developed well before their front limbs. Researchers studying the eggs think that this means newborn pterosaurs would have been strong enough to walk around on all fours, but not strong enough to fly. They also found that none of the embryos had any teeth.

These are both important pieces of information because together, they suggest that baby pterosaurs were born unable to hunt for their food. Some animals, like turtles and snakes, are born capable of looking after themselves. Their parents don’t need to stay around to make sure they survive, so they leave. But if pterosaurs were born with no teeth and without the ability to fly, they’d have been quite helpless. This would make it likely that their parents looked after them for a while after they hatched, until they grew teeth and started flying.

However, scientists have got to be careful when they try to figure out things from only a few pieces of evidence! Other scientists have pointed out that there’s a big gap in size between the largest embryos and the youngest hatched pterosaurs. They think that there is still a chance that pterosaurs grew teeth and stronger front limbs before they hatched.

Of course, the more fossils there are to study, the easier it would be to figure out how young pterosaurs developed. Luckily for the team of researchers in China, they think that there could be almost 100 more eggs in the same piece of rock! They’re hoping to find fossils that fill in the gaps in the development timeline. What do you think? Did parent pterosaurs look after their young, or is it too soon to say?

Watch Fossil Evidence to see how palaeontologists use fossils to figure out events that happened millions of years ago!