How big were dinosaur eggs?

An interior shot of the Central Hall at the Natural History Museum, featuring the Diplodocus skeleton

© The Trustees of the Natural History Museum, London

    • We all know that dinosaurs were some of the biggest animals to walk the earth. Some of the biggest of these were sauropods, massive plant eating animals like the Diplodocus. You probably already know what they look like - they're the ones with long necks and tails and four sturdy legs.

      As sauropods were the biggest dinosaurs, you’d expect that they’d have some of the biggest eggs then, right?

      Well, according to scientists from the University of Lincoln, that’s not the case at all. They’ve discovered that sauropods laid quite small eggs, relative to their size.

      Experts think that an adult sauropod was 50 times heavier than an adult ostrich, the bird that lays the biggest eggs alive today. Ostrich eggs are on average 15 cms long, 13 cms wide and weighed 1.4 kilograms - at least 20 times heavier than a chicken egg!

      The image below shows an ostrich egg in comparison with a chicken egg and some quail eggs (the speckled eggs at the top).

      An image showing a chicken egg, two quail eggs and ostrich egg© Rainer Zenz, via Wikimedia Commons [CC BY-SA 2.5] (image cropped)
      Yet despite sauropods being much bigger than an ostrich, a sauropods’ eggs was not much larger than an ostrich's egg.

      You can see how big sauropods were in this photo of Dippy the Diplodocus at the Natural History Museum.

      An interior shot of the Central Hall at the Natural History Museum, featuring the Diplodocus skeleton© The Trustees of the Natural History Museum, London
      Scientists also found that the number of eggs laid by sauropods was also surprisingly low.

      Why would this be?

      Using information gathered from modern birds and reptiles, scientists from the University of Lincoln and George Mason University in Virginia in the US, investigated what factors could affect the number and size of eggs sauropods laid.

      The scientists found that it would have taken between 65 and 82 days for the sauropod eggs to hatch after being laid. This period is known as incubation, and it seems the sauropods had a very long one.

      A longer incubation time would dangerous for both the parent sauropods and their eggs because they are more likely to be attacked by predators.

      Dr Charles Deeming, from the School of Life Sciences at the University of Lincoln believes that the female sauropods might have laid their eggs in small clutches (the name for a collection of eggs), perhaps in different places to try to prevent predators from finding them all.

      Sauropods kept their eggs in underground nests which would have been quite cool. This would have also had an impact on the size of each egg and the clutch as a whole.

      Professor Ruxton, from the School of Biology at the University of St Andrews said, “Some people might find it a bit disappointing that giant dinosaurs didn’t lay equally giant eggs – but it’s very satisfying to think that we might finally understand why.”

      The results of this study might have an impact on other groups of dinosaurs; scientists may now be able to find out more about how many eggs they laid and the size of their clutch.

      What do you think? Are you disappointed that dinosaurs didn’t lay giant eggs?
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