Egg laying is a character unique to which groups of animals and their ancestors?

Question

Quizplus · Accepted Answer

Egg laying is a characteristic that is not unique to any single group among birds, mammals, and reptiles; rather, it is shared by all of these groups and their ancestors. Birds and most reptiles lay eggs, and even some mammals (monotremes like the platypus and echidna) lay eggs, indicating that egg laying is a primitive trait inherited from common ancestors.

Egg Laying Is a Character Unique to Which Groups of Animals