Marsupials first reached Australia more than 55 million years ago, crossing from South America through Antarctica before the ancient supercontinent Gondwana split apart. Since then, they have diversified into an extraordinary range of forms — from thumb-sized possums that sleep through winter in the High Country to blind, pink-furred moles that spend their entire lives underground in the Red Center. Yet despite their success, the early history of Australian marsupials has remained frustratingly incomplete.
Now, a team led by paleontologist Dr. Tim Churchill at the University of New South Wales has filled in a major gap. In a paper published in the Journal of Paleontology, they describe three newly identified fossil species from the Riversleigh World Heritage Area in Queensland that belong to a completely new order of marsupials, which they have named Keeunamorphia.
Keeunamorphia were small insect-eaters weighing between 25 and 200 grams, roughly the size of modern mice to small rats. They lived in the wet, dense rainforests of northern Queensland around 18 million years ago and persisted for about 35 million years before disappearing roughly 15 million years ago, when regional cooling transformed rainforest into open woodland.
What makes the discovery remarkable is that the fossils were hiding in plain sight. The three species lived alongside other marsupials that scientists had already studied, but their teeth were unusual — and did not match any known marsupial group. By combining fossil evidence with genetic data from living species, the team built a phylogenetic tree that placed the three species on their own branch, separate from the five existing marsupial orders.
Knowledge takeaway: Keeunamorphia represents a sixth order of Australian marsupials, proposed from fossils at the Riversleigh site; these small insect-eaters survived for roughly 35 million years before vanishing as the continent dried; the discovery suggests that Australia\'s marsupial evolution was more complex and diverse than previously understood.