![]() On Gondwana, the Australosphenidans – including the monotremes – dispersed widely, and the oldest example, Steropodon, is from Australia 110 million years ago. On Laurasia, boreosphenidons, such as marsupials and placentals, evolved. Early Triassic mammals ranged widely across Pangea, but following its the rifting into Laurasia and Gondwana, these lineages diverged. The tail of the humble echinda is one of geodynamics. What, then, happened to the Australosphenidans elsewhere in the world? Of plates and platypuses In fact 61 million year old platypus fossils have been found in Argentina, and other Australosphenidans are known from Madagascar, indicating this was a far-ranging successful group. Steropodon looked remarkably like a modern platypus, suggesting that the platypus lifestyle – living in freshwater streams, and burrowing into riverbanks – has been remarkably successful. The earliest fossils are Cretaceous, including the first monotreme in the fossil record, the 110 million year old Steropodon, an opalised fossil from Lighting Ridge in NSW. In the southern hemisphere, this group became the Australospheridans, spread far across the Gondwana. These early mammals, the Yinotheres, spread across the Pangaean landscape in the Triassic, with early Laurasian forms found in the Jurassic from China to England. ![]() The monotremes, on the other hand, are part of an ancient group of mammals that diverged from the other surviving mammals somewhere in the Triassic. Together, this northern-hemisphere mammal group has called the boreosphenidans – and includes all non-monotreme mammals alive today. The oldest known marsupial fossils are found in China (125 million years ago), and the USA (110 million years ago), and they are closely associated with placentals mammals, like us. Despite the familiarity of marsupials in Australia, it is surprising to learn that they actually evolved in the northern hemisphere, contemporaneously with placentals. Monotremes, and marsupials, are typically characterised as Australian. Echidna with burnt spikes survived by burrowing into the dirt. On top of a highly sensitive electro-sensory system on the snout, platypuses have taken their own evolutionary road through history.īushfire survivor. Whilst not fatal, it is said that a platypus sting is so painful that one wishes it were. The platypus has developed some unique evolutionary innovations, evolving one of the few mammal toxins – found in the back-leg spurs on the males. But they have, of course, been evolving just as long as other mammals. That has led to a belief that they are primitive. The monotremes are the only egg-laying mammals – a trait inherited from their early mammal-like reptile forbears. Together with the one extant species of platypus, these species – the monotremes – form the last surviving members of a group of mammals that once dominated the southern hemisphere. With one species – the short beaked echidna – in Australia, and three long-beaked species in New Guinea (including the wonderfully named Sir David’s long-beaked echidna, Zaglossus attenboroughi, named after Sir David Attenborough), the echidnas have bumbled their way through the Australasian landscape for over 20 million years. With a prickly exterior, short-sight, utter contempt for ant attacks, and a tendency to bury its head in the ground when threatened, the echidna is the spirit animal we all need. īut perhaps most at risk are some of the mammal species that are – arguably – the original Australians. This includes some of Australia’s most iconic species, such as koalas – with reports suggesting the conflagration and fragmentation of their habitat may drive them to “functional” extinction. Perhaps the most confronting is the scale of death of native animals – with conservative estimates of over 1 billion animals lost. Many of us have lost houses, properties, schools – but not a sense of community. ![]() With most of the east coast of the continent covered in thick smoke, many Australians were faced with reality of spending the entire season not at the beach or in the sun, but indoors, battling respiratory conditions. The recent Australian bushfire season has precipitated a shift in the Australian – and the world’s – perception of the urgency of addressing climate change.
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