hacketti Echidnas (/ɪˈkɪdnəz/), sometimes known as spiny anteaters,[1] are quill-covered[2] monotremes (egg-laying mammals) belonging to the family Tachyglossidae /tækiˈɡlɒsɪdiː/, living in Australia and New Guinea.

The four extant species of echidnas and the platypus are the only living mammals that lay eggs and the only surviving members of the order Monotremata.

[3] The diet of some species consists of ants and termites, but they are not closely related to the American true anteaters or to hedgehogs.

[citation needed] An alternative explanation is a confusion with Ancient Greek: ἐχῖνος, romanized: ekhînos, lit.

[6] The spines are modified hairs and are made of keratin, the same fibrous protein that makes up fur, claws, nails, and horn sheaths in animals.

[6] They have elongated and slender snouts, or proboscises, that function as both mouth and nose, and which have electrosensors to find earthworms, termites, ants, and other burrowing prey.

Echidnas have tiny mouths and toothless jaws, and feed by tearing open soft logs, anthills and the like, and licking off prey with their long, sticky tongues.

[9] The first European drawing of an echidna was made in Adventure Bay, Tasmania by HMS Providence's third lieutenant George Tobin during William Bligh's second breadfruit voyage.

[10] The short-beaked echidna's diet consists mostly of ants and termites, while the Zaglossus (long-beaked) species typically eat worms and insect larvae.

[12] Echidnas' faeces are 7 cm (3 in) long and are cylindrical in shape; they are usually broken and unrounded, and composed largely of dirt and ant-hill material.

[12] Though the internal reproductive organs differ, both sexes possess an identical single cloaca opening for urination, defecation, and mating.

The female lays a single soft-shelled, leathery egg 22 days after mating, and deposits it directly into her pouch.

[26] During mating, the heads on one side "shut down" and do not grow in size; the other two are used to release semen into the female's two-branched reproductive tract.

[12] In June 2024, scientists reported a first-of-its-kind encounter when they witnessed a tiger shark regurgitating a whole echidna off the cost of an island near Australia.

[31] The divergence between oviparous (egg-laying) and viviparous (offspring develop internally) mammals is believed to date to the Triassic period.

[7] Of the eight genes involved in tooth development, four have been lost in both platypus and echidna, indicating that the loss of teeth occurred before the echidna-platypus split.

This would explain their rarity in the fossil record, their abundance in present times in New Guinea, and their original adaptation to terrestrial niches, presumably without competition from marsupials.

Despite the similar dietary habits and methods of consumption to those of an anteater, there is no evidence supporting the idea that echidna-like monotremes have been myrmecophagic (ant or termite-eating) since the Cretaceous.

[note 1][42] The echidna is hunted at night, gutted, and filled with hot stones and mandak (Persoonia falcata) leaves.