Unwin, David and Deeming, Charles (2008) Pterosaur eggshell structure and its implications for pterosaur reproductive biology. Zitteliana: an international journal of palaeontology and geobiology, B28 . pp. 199-207. ISSN 1612-412X, 1612-4138

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Abstract

The recent discovery of pterosaur eggs containing embryos has provided important evidence regarding the structure of pterosaur eggshell. Two eggs, from the same locality and horizon in China, have a shell that appears to have been parchment-like and pliable with no detectable mineralised calcareous component. A third egg, from Argentina, preserves evidence of a single layer of calcite. This is only 30 microns in thickness, however, and thus very much thinner than mineralised layers reported in turtles that lay pliable-shelled eggs. All three examples resemble the parchment-shelled eggs of squamate reptiles, but exhibit variation in the degree of calcification of the outer surface, which also varies between squamate species. It seems unlikely that the parchment-shelled eggs of pterosaurs were incubated by direct contact with the body of a parent because of the risk of crushing the egg. Moreover, the likely high permeability of a parchment-like eggshell would have required burial in a very humid environment, such as sand, soil, or perhaps in mounds of rotting vegetation, to prevent desiccation during incubation. Consequently, pterosaur eggs are likely to have developed in a thermal environment close to ambient temperatures and probably subject to some temperature variation.

Item Type:	Article
Additional Information:	The recent discovery of pterosaur eggs containing embryos has provided important evidence regarding the structure of pterosaur eggshell. Two eggs, from the same locality and horizon in China, have a shell that appears to have been parchment-like and pliable with no detectable mineralised calcareous component. A third egg, from Argentina, preserves evidence of a single layer of calcite. This is only 30 microns in thickness, however, and thus very much thinner than mineralised layers reported in turtles that lay pliable-shelled eggs. All three examples resemble the parchment-shelled eggs of squamate reptiles, but exhibit variation in the degree of calcification of the outer surface, which also varies between squamate species. It seems unlikely that the parchment-shelled eggs of pterosaurs were incubated by direct contact with the body of a parent because of the risk of crushing the egg. Moreover, the likely high permeability of a parchment-like eggshell would have required burial in a very humid environment, such as sand, soil, or perhaps in mounds of rotting vegetation, to prevent desiccation during incubation. Consequently, pterosaur eggs are likely to have developed in a thermal environment close to ambient temperatures and probably subject to some temperature variation.
Keywords:	Argentina, Egg, Eggshell, Fossil
Subjects:	F Physical Sciences > F641 Palaeontology
Divisions:	College of Sciences > Faculty of Science > School of Life Sciences
Depositing User:	Charles Deeming
Date Deposited:	03 Jun 2011 09:07
Last Modified:	13 Mar 2013 09:00
URI:	http://eprints.lincoln.ac.uk/id/eprint/4507

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