What do all egg-laying mammals have in common?

Answer 1

There are only two monotremes - the echidna and the platypus. There are some similarities between them. * They are both monotremes, egg-laying mammals. * Both can swim, but the platypus is semi-aquatic, while the echidna lives on land. * Both animals can be found from trpoical northern regions of Australia down to sub-alpine regions of Tasmania. A difference is that the echidna can also survive quite well in semi-arid areas. * Both have strong claws for digging burrows for shelter, but the platypus also has a retractable membrane between its claws, which helps it to swim. * Both the male platypus and the male echidna have a spur on their hind ankle, but the platypus's is poisonous whilst the echidna's serves no known function. * Neither echidnas nor platypuses have teeth. The platypus grinds its food between bony plates in its bill, whilst the echidna uses its long, sticky tongue to catch and eat termites and ants.