Some think the monotremes split off first, with marsupial and eutherians following suit. It's still unclear when all three of these distinct groups first began to diverge from one another. Therian mammals all give birth to live young, but monotremes are simply too different to be lumped in with that group as well.
Together, the latter two make up a subclass known as therian mammals.
Today, living mammals are split into three groups, including monotremes, marsupials, and eutherians, or 'placentals'. Using a male platypus, researchers have now created a physical map with a highly accurate platypus genome. In previous years, a female platypus had some of its genome sequenced, but without any Y chromosome sequences, a lot of information was missing. "At the same time, decoding the genome for platypus is important for improving our understanding of how other mammals evolved - including us humans." "The complete genome has provided us with the answers to how a few of the platypus' bizarre features emerged," explains evolutionary biologist Guojie Zhang from the University of Copenhagen. Scientists think its genome could tell us secrets about our own evolution and how our distant mammalian ancestors went from laying eggs to giving birth. The genes of both are relatively primitive and unchanged, revealing a bizarre blend of several vertebrate animal classes, including birds, reptiles, and mammals.Īs different as the platypus might seem at first, it's those very differences that reveal our similarities and our shared ancestry with Earth's other vertebrates. Along with the spiky echidna, these two Australian animals belong to a highly-specialised group of mammals, known as monotremes, which both lay eggs but also nurse their young with milk. The duck-billed platypus is truly one of the oddest creatures on Earth.
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