Dictionary of Human Evolution and Biology

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Prototheria

Subclass of class Mammalia consisting of the order Monotremata and the families Tachyglossidae (spiny anteater or echidna) and Ornithorhynchidae (duck-billed platypus). This taxon is the most primitive of the mammals featuring traits unusual among mammals such as oviparity, very undeveloped young, mammae without nipples, skull features that are birdlike, and a reptilian positioning of the fore limbs (although the hind limbs are therianlike). These animals lack teeth as adults.

Cf. Theria.

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