; subclass Prototheria, order Monotremata)
A family of insectivorous monotremes, now recognized as being more closely related to the placental mammals (see Eutheria) than to the platypus (see Ornithorhynchidae), in which the limbs are modified for digging, the body is covered with hair modified except on the belly into barbless spines, the snout is long, and the tongue is long, sticky, and has horny serrations that grind against ridges in the palate. There are no teeth, and the lower jaw is much reduced. Echidnas occur only in Australia and New Guinea. There are two species, in two genera, Tachyglossus and Zaglossus; a third genus, Megaloglossus, is known from the Pleistocene.
Subjects: Zoology and Animal Sciences.