A remarkable fossil discovery in Queensland has filled one of the biggest gaps in Australia’s evolutionary history. According to a new study published in the journal Australian Zoologist, researchers have identified the oldest known member of the dasyurid family – the group of carnivorous marsupials that today includes the Tasmanian devil, quolls, dunnarts and antechinuses. The discovery pushes the group’s fossil record back to around 23 million years ago, revealing that the ancestors of these predators once thrived in lush rainforests rather than the dry Australian landscapes they are often associated with today.
Tiny fossil jaws reveal the oldest known dasyurid
The newly discovered species, named Miyumba chrisdickmani, was a tiny carnivorous marsupial weighing only about 30 grams, roughly the size of a modern mouse. Scientists identified the species from six fossilised lower jaws uncovered at the Riversleigh World Heritage Area in northwestern Queensland which is one of the world’s richest fossil sites.Although the fossils are small, they answer a question that has puzzled researchers for decades: when did Australia’s carnivorous marsupials first appear?For years, molecular studies suggested dasyurids originated much earlier than their sparse fossil record indicated, leaving a major gap between genetic estimates and fossil evidence. Most confirmed fossils of the family were younger than 5 million years, leaving a large gap in their evolutionary history. Another fossil species, Barinya wangala, was once thought to be an early dasyurid, but later research showed it belonged to a different extinct marsupial family altogether.The discovery of Miyumba chrisdickmani changes that picture. Dating back about 23 million years, it extends the fossil record by more than 5 million years and provides the earliest confirmed evidence of the dasyurid family. Researchers identified the species through a distinctive dental feature; a third lower premolar that is smaller than the first and second premolars, a characteristic shared with modern dasyurids but absent in more primitive marsupials.
Riversleigh World Heritage Area (Image Credit: Wikipedia)
Australia’s top marsupial predators likely began in rainforests
The study also paints a very different picture of Australia’s ancient environment.Today, many dasyurids are found in deserts, woodlands and grasslands across Australia. However when Miyumba lived around 23 million years ago; the Riversleigh region was covered by dense tropical rainforest filled with diverse wildlife. Its teeth suggest it probably fed on insects and other small vertebrates or invertebrates beneath the rainforest canopy. Evolutionary analysis also suggests that Miyumba was closely related to modern rainforest-dwelling dasyurids found in New Guinea, indicating that the group’s earliest ancestors were adapted to wet forest habitats.As Australia’s climate gradually became drier over millions of years, many members of the family spread into open forests, grasslands and deserts. Some rainforest lineages likely survived in New Guinea where tropical forests remained.These findings challenge the long-held assumption that Australia’s carnivorous marsupials primarily evolved in dry environments and instead suggest their evolutionary roots lie in ancient rainforests.
A discovery that reshapes Australia’s evolutionary history
Beyond identifying a new species, the research helps solve one of the biggest mysteries in Australian mammal evolution.The timing of Miyumba’s appearance closely matches the decline of another ancient group of carnivorous marsupials known as the keeunamorphians. Scientists suggest that as these older predators disappeared, early dasyurids may have expanded into newly available ecological niches and gradually diversified into the nearly 80 living species seen today, including quolls, dunnarts and the Tasmanian devil.While more fossil discoveries will be needed to fully understand this transition; the Queensland fossils provide the strongest evidence yet that Australia’s modern carnivorous marsupials have a much older history than previously confirmed.By uncovering just six tiny fossil jaws, researchers have not only extended the fossil record of the dasyurid family but also revealed that the ancestors of some of Australia’s best-known predators first evolved in thriving tropical rainforests millions of years before adapting to the continent’s increasingly arid landscapes.
