Monotremes,like the duck-billed platypus,are egg-laying mammals (oviparous)covered in hair,have mammary and skin glands,three ear ossicles,are diphyodont (their permanent teeth replace their "baby" teeth),and possess dentary-squamosal jaw articulation (the jaw bone hinges with the squamosal bone of the skull).Marsupials,such as kangaroos and koalas,are pouched mammals that have a vertical tympanic membrane in addition to being covered in hair,have mammary and skin glands,three ear ossicles,are diphyodont,and possess dentary-squamosal jaw articulation.Eutherians are the placental mammals that most people easily recognize as mammals.They are covered in hair,have mammary and skin glands,three ear ossicles,are diphyodont,possess dentary-squamosal jaw articulation,and have a vertical tympanic membrane. What one shared derived trait sets marsupials and eutherians apart from monotremes?

Question

Quizplus · Accepted Answer

The presence of a vertical tympanic membrane sets marsupials and eutherians apart from monotremes. All three groups share the other traits listed.

Monotremes,like the Duck-Billed Platypus,are Egg-Laying Mammals (Oviparous)covered in Hair,have Mammary