Scientists have uncovered new clues about the evolution of two of the planet’s most bizarre creatures, the platypus and echidna. A fossil specimen of a long-extinct ancestor, Kryoryctes cadburyi, has revealed unexpected traits that challenge current understanding of mammalian evolution.
Found in Australia and New Guinea, the platypus and echidna are unique as they’re the only mammals that lay eggs. The platypus is an amphibious creature with a bill, webbed feet, and beaver-like tail, while the echidna has pointy quills and backward-facing feet.
A recent study published in Proceedings of the National Academy of Sciences used advanced 3D imaging to examine the internal structure of Kryoryctes cadburyi. The team found that the fossil had characteristics similar to those of the semiaquatic platypus, including a thicker bone wall and smaller central cavity, which suggests it may have lived partially in water.
The discovery supports the hypothesis that Kryoryctes is a common ancestor of both the platypus and echidna. The study indicates that the amphibious lifestyle of modern platypuses had its origins at least 100 million years ago, while echidnas made a later reversion to a fully terrestrial lifestyle.
The evolution of platypuses and echidnas provides insights into the transition from water to land, which is relatively rare in animal evolution. The team’s findings suggest that these creatures may have adapted to a semiaquatic life early on, which could explain their unique characteristics, such as the echidna’s backward feet.
The primitive history of monotremes is crucial to understanding how mammals evolved into humans. These creatures are living relics from a distant past and offer no way to predict the biology of our last common ancestor without studying animals like them.
Source: https://edition.cnn.com/2025/04/30/science/platypus-echidna-monotremes-evolution/index.html