This animal experiences approximately 8 hours of REM sleep per day, which is the highest of any mammal. Like snakes, certain defensin-like proteins are found in this animal's venom. Both males and females have ten sex chromosomes, and they may be the only mammals that follow the ZW sex determination system, a characteristic shared with birds. They belong to genus Ornithorhynchus, and other similarities to birds, including the use of a cloaca for reproduction, show these animals' early divergence from the placentals and 
This animal experiences approximately 8 hours of REM sleep per day, which is the highest of any mammal. Like snakes, certain defensin-like proteins are found in this animal's venom. Both males and females have ten sex chromosomes, and they may be the only mammals that follow the ZW sex determination system, a characteristic shared with birds. They belong to genus Ornithorhynchus, and other similarities to birds, including the use of a cloaca for reproduction, show these animals' early divergence from the placentals and marsupials. For 10 points, name these primitive mammals, certain egg-laying monotremes with duck bills.
This animal experiences approximately 8 hours of REM sleep per day, which is the highest of any mammal.
duck-bill platypus [or Ornithorhynchus anatinus]