Is one excretory hole a trait of birds or a trait birds and reptiles share?

Egg-laying is a reptilian trait, although some reptiles carry the eggs inside their bodies until hatching. (Rattlesnakes, e.g.) So there’s no surprise in seeing that carry over to the most primitive mammals.

Turtles are reptiles, and they have beaks. http://www.madsci.org/posts/archives/Apr2003/1050350289.Ev.r.html
So did some of the dicynodonts – a reptilian lineage that is often described as “mammal-like”. Obviously not all dicynodonts were beaked, since the name itself means “two dog teeth.” Or did they have a pair of fangs sticking out from their beaks?

Where the three traits (milk glands, hair, and warmblooded) that identify mammals started is uncertain, since warmbloodedness does not leave a direct fossil record, hair rarely left fossil traces, and soft tissue like milk glands is even less likely to show up in fossils. Paleontologists are now leaning towards thinking that the ‘raptors were feathery warm-blooded dinosaurs. It’s not impossible that some the dicynodonts were hairy, warm-blooded, and secreted milk. That would make the platypus their least changed descendant, while marsupials evolved more, and placental mammals even more.

I crack me up.

Neither does a Centaur. But the difference is that mammals and reptiles are main branches, one that evolved off the other. Humans and horses (while “minor” branches) are widely separated within the mammal branch. (Clumsily worded, but it’s the best I can do.)

More here:

http://www.talkorigins.org/faqs/platypus.html

Including reference to fossil platypi with vestigial teeth.

In no time, I’ll have them all chanting, “What, you call THIS intelligent?” and wearing t-shirts that say “MY intelligent designer was drunk at the time.”