There is no animal more captivating, more bizarre, than the platypus. I dare you to prove me wrong, but you'll just come out looking like a stupid placental mammal.
What the platypus lacks in nipples it makes up for in its other adaptations. Males have venomous spurs on their ankles, a formula unique to the species and powerful enough to kill a dog. The platypus is also a master of electrolocation. While hunting in murky creeks and riverbeds, the platypus closes its nostrils and eyes and uses the incredible sensitivity of its bill to map out a "picture" of its surroundings and find its helpless prey.
Toothed ancestors of the platypus, most famously Steropodon, have been found in rock beds dating back 110 mya in the Cretaceous. Steropodon evolved around the same time as Tyrannosaurus rex. The K/T event killed off the dinosaurs, but not the platypus' grandparents.
Nipples aren't everything.