Possible egg masses from amphibians, gastropods, and insects in mid-Cretaceous Burmese amber

ABSTRACT

The eggs of fish, amphibians, and many invertebrates are soft, delicate structures that are only rarely preserved in the fossil record. Here we report egg masses preserved as inclusions in mid-Cretaceous amber deposits of Myanmar. Of five specimens recovered, three of the egg masses probably pertain to insects, but the other two appear different. One mass is composed of relatively stiff eggs that retain their shape throughout the mass and may be linked by mucoid strands. This morphology resembles that of some terrestrial molluscs. The second mass is composed of softer eggs that have compressed one another so that their shapes are strongly distorted within the mass. These eggs most closely resemble those of amphibians. Given the forest environment reconstructed for the amber locality, the eggs were presumably attached on or close to the resin producing tree.

KEYWORDS:

• Myanmar
• fossil eggs
• anura
• mollusca
• insecta
• Mesozoic

Acknowledgments

We would like to thank the two anonymous reviewers for their suggestions and comments. We thank Christopher M. Schalk (Sam Houston State University, TX, USA) and Hao Ran (Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection, Ministry of Education, Guilin, China) for discussion, Shenna Wang (Dexu Institute of Palaeontology, China) for providing the specimens for study.

Author Contributions

L.X. and S.E. designed the project. L.X. and H.C. acquired the specimen, supervised, and conducted the initial analytical work. D.W. performed the earlier analyses. G.L. and M.B. scanned and interpreted the data. L.X., D.W., R.M., and S.E. wrote the manuscript. L.X., D.W., and S.E. contributed equally to the completion of the manuscript, analyses, and images.

The authors declare no competing interests.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was funded by the National Natural Science Foundation of China [No. 41790455, 41772008]; the National Geographic Society, USA [No. EC0768-15], and the Natural Sciences and Engineering Research Council of Canada [2015-00681].