https://www.aikenstandard.com/lifestyle/ecoviews-why-do-birds-and-turtles-have-eggs-of-different/article_386369c6-d740-11e8-b3f8-9f977a120a39.html

Why do sea turtles, softshell turtles and snappers lay round eggs whereas pond sliders and many other turtles have elliptical eggs shaped more like those of a chicken? This question came up recently in a discussion I had with another turtle biologist, Jeff Lovich of the U.S. Geological Survey.

A similar question has been asked about birds, most of which also have round or elliptical eggs, depending on the species. A few lay cone-shaped eggs. Seeking answers to such questions in order to explain why the world around us is the way it is is what makes ecology intriguing.