Both oviparity and viviparity are found in Euselachii. Sharks display three ways to bear their young, varying by species, oviparity, viviparity and ovoviviparity. Like all birds, fluttering shearwaters breed via a process known as true oviparity. Lizards in the genus "Lialis" exhibit oviparity and typically lay two eggs per clutch. The carpenter's chimaera exhibits oviparity, with egg shells containing "horns" on them. With single oviparity, the egg cases are extruded soon after fertilization. Oviparity in sharks can be categorized as single or retained. The five include two nonviviparous modes&colon; ovuliparity, with external fertilisation, and oviparity, with internal fertilisation. Oviparity is completely absent in the superorder Squalomorphii.