Question: Do all sharks have mermaid purse eggs?

Lesser-Spotted Catshark answered on 7 Nov 2017:

No, not all sharks have Mermaid’s Purses! Catsharks are ‘oviparous’ which means egg-laying. Their Mermaid’s Purses are interesting but if you want to see a really strange looking one check out another oviparous species: the horn shark (Heterodontus francisci). Their egg-cases look more like a corkscrew than a purse.

Other sharks are ‘viviparous’ which means they give birth to live young (just like mammals). Still others are ‘ovoviparous’ which means they have eggs which hatch inside the mothers (!) and then go on growing before they are eventually born.