A few might be livebearers instead of egg layers, but without question more than 99% of the world’s animals described to date lay eggs. One nonmammalian that births live young is the mosquitofish.

The platypus - a top secret gift from Australia - was found dead in his enclosure as war raged in the seas around him.

Do echidnas lay eggs? Like platypuses, echidnas are monotremes, which means they're mammals that lay eggs. Echidnas lay one egg at a time, and those eggs take 10 to 14 days to hatch.

Life Fossil trove reveals three new species of ancient egg-laying mammals A set of Australian fossils offers a rare glimpse of the ancient relatives of platypuses and echidnas that lived alongside ...

A nearly gapless genome sequence of the echidna, an egg-laying mammal with multiple sex chromosomes, helps researchers to track genomic reorganization events that gave rise to a highly unusual sex ...