what are the unique character in mammalian?
viviparity
hair 
ear pinna
heterodont
the ans in this is hair on body.. but i have the doubt that hair are on present in animals of cetacea order so hair is not a characteristic feature  but heterodont teeth r present in all mammals so why isnt the answer?

Dear Student,

Following are some characteristics of mammals-

-Presence of milk-producing glands (mammary glands)
-Two pairs of limbs
-Skin with hair 
-External ears or pinnae
-Four-chambered heart
-Separate sexes
-Internal fertilisation
- Viviparity (except Platypus and echinda)
- Heterodont dentition

According to the question, All of the options are the unique characteristics of mammals.


 
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