Egg case (Chondrichthyes)

Embryo active inside egg case.

An egg case or egg capsule, often colloquially called a mermaid's purse, is the casing that surrounds the eggs of oviparous chondrichthyans. Living chondricthyans that produce egg cases include some sharks, skates and chimaeras. Egg cases typically contain one embryo, except for big skate and mottled skate egg cases, which contain up to 7 embryos.^[1] Oviparity is completely absent in the superorder Squalomorphii.^[2]^[3] Egg cases are also thought to have been produced by some extinct chondricthyan groups, such as hybodonts and xenacanths.

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