Together with our echidna sequence, the genomes of the two species allow us to detect the ancestral and lineage-specific genomic changes that shape both monotreme and mammalian evolution. The nearly complete platypus genome assembly has anchored almost the entire genome onto chromosomes, markedly improving the genome continuity and gene annotation. Here we generate and analyse reference genomes of the platypus ( Ornithorhynchus anatinus) and echidna ( Tachyglossus aculeatus), which represent the only two extant monotreme lineages. Nature volume 592, pages 756–762 ( 2021) Cite this articleĮgg-laying mammals (monotremes) are the only extant mammalian outgroup to therians (marsupial and eutherian animals) and provide key insights into mammalian evolution 1, 2. Platypus and echidna genomes reveal mammalian biology and evolution