This order uses the XY sex-determination system, but has ten sex chromosomes instead of the usual two.
This order split off before Metatheria and Eutheria according to the theria hypothesis. This order uses the XY sex-determination system, but has ten sex chromosomes instead of the usual two. The only extant genuses in this order are Ornithorhynchus, Tachyglossus and Zaglossus, which contain five species only found in New Guinea and Australia. Instead of having nipples, this order secretes milk through the skins of its abdomen. The male of one species in this order has venomous spurs on its hind legs. This order of mammals has a true cloaca. For 10 points, name this order of egg-laying mammals that includes echidnas and platypuses.
This order split off before Metatheria and Eutheria according to the theria hypothesis.
monotremes [or Monotremata; or echidnas or Tachyglossidae before \"ten sex chromosomes\"]