An occurrence of fossil eggs from the Mesozoic of Madagascar and a detailed observation of eggshell microstructure

ABSTRACT

Whereas fossil turtle eggs have a near global distribution and range from Middle Jurassic to Pleistocene, they are rarely documented from the Mesozoic of Gondwana. Here, we report three fossil turtle eggs from the Upper Cretaceous (Campanian) of the Morondava Basin, Madagascar. The spherical eggs range in size from 33.5 to 35.5 mm and have an average eggshell thickness of 440 µm. They can be confidently identified as rigid-shelled turtle eggs by the presence of tightly packed shell units composed of radiating acicular crystals and a shell unit height to width ratio of 2:1. Lack of associated skeletal remains precludes taxonomic identification of the eggs. Although a large vertebrate fauna has been reported from the Upper Cretaceous of Madagascar, these specimens are the first eggs from the Mesozoic of the island.

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ACKNOWLEDGMENTS

We thank J. Horner and E. Lamm for access to the Gabriel Laboratory for Cellular and Molecular Paleontology (Bozeman, Montana, U.S.A.). M. Marshall shared her knowledge of the geology and paleontology of the Morondava Basin. J. Sertich and H. Furrer advised about repatriation of the specimens. A. Bailleul, C. Woodruff, M. Holland, J. Simon, and M. Hebeisen provided laboratory assistance, and K. Harvati-Paptheodorou allowed access and assistance to the CT scanner. B. Garner, D. Barta, and F. Jackson commented on earlier versions of the manuscript, and W. Joyce and an anonymous reviewer are thanked for their helpful comments. I.W. is supported by SNF grant 31003A 149605 granted to M. R. Sánchez-Villagra.

Handling editor: Sean Modesto.