The eggcases of egg-laying sharks and rays (also known as mermaids’ purses) can be found washed up on many coastlines around the world, and the size and shape of the purse can be used to distinguish each species. For example, skates and rays can be instantly recognized by a pair of horns positioned at either end of the central capsule or case. These help to anchor the purse to the soft shore sediment. Catshark eggcases possess curly tendrils that are used to attach the purse to seaweed.
The structure of the capsule can also be used to identify some species. For example, the Thornback Ray eggcase has a narrow ridge or keel along the edge of its capsule.
If you’re interested in learning more, check out our article on mermaid’s purse identification. It goes into a lot more depth on how to identify species from all around the world.