Despite this extraordinary diversity, one of the biggest questions about their evolution has remained unanswered. Where did they come from?<\/p>\n
Our new research<\/a>, published today in Australian Zoologist, describes what is now the earliest known member of the dasyurid family \u2013 a mouse-sized predator we have named Miyumba chrisdickmani. It pushes the fossil record of dasyurids back by more than five million years and provides the first clear picture of what the earliest members of this iconic Australian group looked like. <\/p>\n A long-running puzzle<\/p>\n For decades, scientists have puzzled over the origins of dasyurids.<\/p>\n Early researchers<\/a> assumed they must be an ancient group<\/a> because their molar teeth exhibit a remarkably primitive design<\/a>, little changed from the earliest Australian marsupial ancestors.<\/p>\n But DNA studies<\/a> later suggested<\/a> something very different<\/a>. Modern dasyurids are actually a comparatively young branch of the marsupial family tree, diverging from their closest relatives around 18 million years ago.<\/p>\n The problem was that the fossil record didn\u2019t seem to agree.<\/p>\n Almost every fossil dasyurid known was younger than five million years old. One supposed dasyurid, Barinya wangala, from the Miocene Epoch, appeared to have filled this evolutionary gap<\/a>. But recent work<\/a> showed it actually belongs to an entirely different family<\/a> of bizarre snail-eating marsupials called the malleodectids. <\/p>\n Suddenly, the fossil record contained no confirmed dasyurids at all before the start of the Pliocene roughly 5.3 million years ago. This left an apparent evolutionary ghost lineage stretching back millions of years.<\/p>\n Our new fossil helps solve that mystery.<\/p>\n The Riversleigh World Heritage Area on Waanyi country in northwestern Queensland is one of the world\u2019s richest fossil deposits. Tiny teeth hold important clue<\/p>\n Miyumba chrisdickmani was about the size of a modern antechinus or large dunnart, weighing only around 30 grams. <\/p>\n It is known from six fossil lower jaws recovered from the Riversleigh World Heritage Area on Waanyi country in northwestern Queensland. This is one of the world\u2019s richest fossil deposits. It preserves Australian ecosystems that span more than 25 million years. <\/p>\n Although tiny, the animal\u2019s teeth preserve an important evolutionary clue.<\/p>\n For decades, palaeontologists struggled to identify fossil dasyurids because there was no unique dental feature that clearly separated them from their extinct relatives. Miyumba reveals one at last.<\/p>\n In most primitive marsupial predators, the third lower premolar is the largest of the three premolars. In modern dasyurids, however, that tooth is actually smaller than both the first and second premolars. <\/p>\n Miyumba possesses exactly this arrangement. This makes it the earliest known fossil to display what appears to be a defining feature of the dasyurid family. <\/p>\n That seemingly subtle difference finally gives palaeontologists a reliable way to recognise early members of this important group.<\/p>\n The earliest known dasyurid<\/p>\n To test where Miyumba belonged, we compared its anatomy with living and extinct marsupials using two different evolutionary analyses. <\/p>\n One examined hundreds of anatomical features preserved in fossils. The other combined anatomical evidence with DNA sequence data from living species while also incorporating the ages of fossil species to estimate when major groups evolved.<\/p>\n Both approaches reached the same conclusion. Miyumba chrisdickmani represents the earliest and most primitive known dasyurid. <\/p>\n The analyses also identified another small Riversleigh fossil, Mayigriphus orbus, as one of the earliest members of the lineage that eventually gave rise to today\u2019s dunnarts, planigales and other small arid-adapted dasyurids.<\/p>\n Together these discoveries push the origin of the dasyurid family back to around 23 million years ago, roughly five million years earlier than previous estimates.<\/p>\n![\"A](\"https:\/\/www.newsbeep.com\/ca\/wp-content\/uploads\/2026\/07\/file-20260716-68-nhe6xk.jpg\")
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\n Timothy Churchill<\/p>\n