08-13-2009, 12:56 AM
It's funny you should use those two examples: the platypus is a monotreme.
"The key anatomical difference between monotremes and other mammals is the one that gave them their name; Monotreme means 'single opening' in Greek, and comes from the fact that their urinary, defecatory, and reproductive systems all open into a single duct, the cloaca." http://en.wikipedia.org/wiki/Monotreme
"The key anatomical difference between monotremes and other mammals is the one that gave them their name; Monotreme means 'single opening' in Greek, and comes from the fact that their urinary, defecatory, and reproductive systems all open into a single duct, the cloaca." http://en.wikipedia.org/wiki/Monotreme