Now vs Millions year back | echidnas |#shorts #short #animals #discovery #youtubeshorts

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. The diet of some species consists of ants and termites, but they are not closely related to the American true anteaters or to hedgehogs. Their young are called puggles.
Echidnas evolved between 20 and 50 million years ago, descending from a platypus-like monotreme.This ancestor was aquatic, but echidnas adapted to life on land.
The divergence between oviparous (egg-laying) and viviparous (offspring develop internally) mammals is believed to date to the Triassic period.Most findings from genetics studies (especially of nuclear genes) are in agreement with the paleontological dating, but some other evidence, like mitochondrial DNA, give slightly different dates.

Molecular clock data suggest echidnas split from platypuses between 19 and 48 million years ago, so that platypus-like fossils dating back to over 112.5 million years ago represent basal forms, rather than close relatives of the modern platypus.[further explanation needed] This would imply that echidnas evolved from water-foraging ancestors that returned to land living, which put them in competition with marsupials.[further explanation needed] Although extant monotremes lack adult teeth (platypuses have teeth only as juveniles), many extinct monotreme species have been identified based on the morphology of their teeth.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.

Further evidence of water-foraging ancestors can be found in some of the echidna's anatomy, including hydrodynamic streamlining, dorsally projecting hind limbs acting as rudders, and locomotion founded on hypertrophied humeral long-axis rotation, which provides an efficient swimming stroke.

Oviparous reproduction in monotremes may give them an advantage over marsupials in some environments. Their observed adaptive radiation contradicts the assumption that monotremes are frozen in morphological and molecular evolution.

It has been suggested that echidnas originally evolved in New Guinea when it was isolated from Australia and from marsupials. 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.