text: Fossil evidence indicates that this order's ancestors maintained tribosphenic molars and cynodonts in their mouths, but no known discovery explains their ability to maintain constant body temperature in a variety of environments.
full_question: Fossil evidence indicates that this order's ancestors maintained tribosphenic molars and cynodonts in their mouths, but no known discovery explains their ability to maintain constant body temperature in a variety of environments. This order's most unorthodox aspect is their birthing process. For 10 points, name this order of mammals that lays eggs, which includes the duck-billed platypus and the echidna.
first_sentence: Fossil evidence indicates that this order's ancestors maintained tribosphenic molars and cynodonts in their mouths, but no known discovery explains their ability to maintain constant body temperature in a variety of environments.