Question

Which of the following characteristics is not shared by birds and mammals?

Answer 1

Both mammals and birds can regulate body temperature and have warm-blooded nature. They have lungs and hence use them for breathing. Both the groups have ossified endoskeletons (formation of bones by adding osteoblasts - osteogenesis, results in an ossified endoskeleton.)

But birds lay eggs and show oviparity whereas mammals give birth to live young and show viviparity (except Monotremes or egg-laying mammals)

So the correct answer is 'Viviparity'.