Monday 23 November 2009

Pterosaur Eggs


Speculation about how pterosaurs reproduced has been enhanced over the years by lack of evidence. Many scientists believed that pterosaurs must have laid eggs, but were they hard shelled as in birds, or leathery as in reptiles. To some, the thought of how a long bony wing would work in an egg was a problem to imagine. Bats give birth to live young without the need for eggs, so perhaps pterosaurs could also give birth to, live young.

Speculation became analysis when, in 2004, a pterosaur egg fossil was found in China.


Avodectes pseudembryon (Wang and Zhou 2004), IVPP-v13758, was discovered in the Jehol Biota, being about 121 million years old. It was a complete embryo in a shell. The wings were coiled as they developed (sketch above) and the preservation indicates clearly that the bones were well ossified before hatching. This would enable the newly hatched pterosaurs to use the wings very quickly after emerging from the egg.

Observations of the porosity of the egg shell suggested possible burial during development and the form of the shell was soft and leathery like a reptilian egg, having a shell that was non-laminar and 0.25mm thick. The embryo wingspan was estimated to be 27cm. The bone proportions are unlike any known pterosaur, but show similarities with Anhanguera and Istiodactylus specimens. This should not be taken as an indication of species, since the bone development and proportions may have been subject to changes during juvenile life.

A second egg, JZMP-03-03-2, was somewhat similar, but the skeletal bones were not articulated in the same clear way, so interpretation is a little more complex.
In the same year, a pterosaur egg, MHIN-UNSL-GEO-v246, was discovered in the Lagarcito Formation in Argentina. This formation is well known for the Pterodaustro fossils and this egg was clearly a Pterodaustro egg. The embryo was intact and articulated.
The egg was also from the Lower Cretaceous deposits about 100 million years ago, and the proportions of the embryo closely matched those of known juvenile specimens. Measurements of the shell indicated a very thin (30μm) leathery shell which was long and oval in shape measuring 22mm by 66mm. The estimated embryo wingspan was 27cm. This egg has many differences from the Chinese finds, but it does support the idea that all pterosaurs probably laid eggs.
The questions that are difficult to resolve are;

  1. How many eggs did pterosaurs lay?
  2. Did pterosaurs care for their young?
  3. Where did pterosaurs nest and what nesting structures did they create?
I suspect that the answers to these types of questions will be different for each type of pterosaur. These creatures would have been subject to the same variations and constraints in their habitats as modern animals are subject to today.

Wang, X., and Zhou, Z., 2004, Pterosaur embryo from the Early Cretaceous: Nature, vol.429, p.621.

Chiappe, L. M., Codorniu, L., Grellet-Tinner, G., and Rivarola, D., 2004, Argentinian unhatched pterosaur fossil: Nature, vol.432, p. 571-572. (2 Dec 2004) 

Pterosaur Database Topics - eggs
 

22 comments:

  1. Thanks so much for the article. My Apologia Flying Creatures science book instructed for me to research this. :)

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  2. We also are studing this through Apologia and found it for the same reason. Thank you for the insight.

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  3. I find it interesting that all of us commenting are researching this topic because of our study on pterosaurs in our Apologia science book. Thank you for this concise synopsis of the finds in China and Argentina.

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  4. we are doing the apologia to and found it the same way very helpful!

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  5. Ditto to the above comments. Thanks for your insights....

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  6. We're doing our Apologia science as well and this was very helpful. Thanks.

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  7. We're here b/c of Apologia, too! I think that's pretty cool!

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  8. Another Apoligia family, doing research on the Pterosaurs.

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  9. Another Apologia family!!!

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  10. Another family studying Apologia Flying Creatures and looking up info on the pterosaur egg discoveries. Thanks!

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  11. Us too! in the UK

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  12. Add one more for Apologia!

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  13. Thanks for the valuable info - another Apologia family here! :)

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  14. We are also using Apologia Science! We have learned a lot about pterosaurs! We are really enjoying this science book.
    Maybe one day the "family" of Apologia will discover more evidence that points to our Creator!

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  15. WE in New Zealand are doing Apoloia too. Awesome.

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  16. Wow, so many Apologia researchers here! I am one of them!

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  17. This comment has been removed by a blog administrator.

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  18. We enjoy Apologia Science. It's awesome. We hope there are more discoveries made to teach us even more about pterosaurs. It's so interesting.

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  19. Another Apologia family! Thanks for the info.

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