'''Monotremes''' are a small [[relict]]{{fact}} group of [[Australasia]]n mammals, consisting of the duck-billed [[platypus]] and the several [[echidna]]s.
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In addition to their unusual physical conformations, monotremes are remarkable for being the only [[mammal]]s to lay [[egg]]s, and to have [[poison]] glands (spurs on the back legs of the male platypus); these were an unpleasant surprise for several early zoologists. A feature is the absence of well-developed [[mammary glands]], the young platypi and echidnae being nourished by nutritious emissions from their mothers unmodified [[sweat gland]]s.