Bone microstructure supports a Mesozoic origin for a semiaquatic burrowing lifestyle in monotremes (Mammalia).

ABSTRACT: The platypus and four echidna species are the only living egg-laying mammals and the sole extant representatives of Order Monotremata. The platypus and echidnas are very disparate both morphologically and ecologically: The platypus is a specialized semiaquatic burrowing form that forages for freshwater invertebrates, whereas echidnas are fully terrestrial and adapted for feeding on social insects and earthworms. It has been proposed that echidnas evolved from a semiaquatic, platypus-like ancestor, but fossil evidence for such a profound evolutionary transformation has been lacking, and this hypothesis remains controversial. Here, we present original data about the Early Cretaceous (108 to 103 Ma) Australian mammal Kryoryctes cadburyi, currently only known from a single humerus, that

SUBMITTER: Hand SJ 

PROVIDER: S-EPMC12088390 | biostudies-literature | 2025 May

REPOSITORIES: biostudies-literature