Palaeoxyris is a morphogenus of eggs cases, widely thought to have been produced by hybodonts, with a predominant occurrence in ancient freshwater environments.

They display a conspicuous right-handed spiral of collarettes around the body, and in some cases, the pedicle, resulting in a rhomboidal pattern when flattened during fossilisation.

[1] At the end of the beak was a tendril which attached the egg to vegetation during development.

[4] Nearly 30 different Palaeoxyris species are currently known with a stratigraphic range from the Carboniferous to the Cretaceous.

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