Source: The Conversation (Au and NZ)
Pat Woolley Australia is home to unusual mammals not found anywhere else – consider the platypus, Tasmanian devil or the red kangaroo. But did you know our understanding of this continent’s incredible mammalian diversity is still incomplete?
We have discovered a new species in one of Australia’s cutest and fiercest mammal groups: planigales. And we also unearthed a second new planigale species, from a 100-year-old specimen held in a Swedish museum.
In the past five years alone, there have been 20 new mammals added to Australia’s mammal species list. So how is it we are still discovering new species of mammals in the 21st century? Let me explain.
Tiny, ferocious marsupials But first, what is a planigale? Planigales are the world’s smallest marsupials. Some species weigh just over two grams (the same as a couple of paper clips) and are about half the size of a house mouse.
With flattened heads, planigales can squeeze themselves into cracks and crevices to hide from predators and extreme weather conditions. They are tiny but fearsome predators that emerge at night to hunt for insects, spiders and vertebrates, such as small lizards and even young mammals.
They generally live in varied habitats that overlay cracking clay soils in central and northern Australia. Because planigales are so small, with subtly varying shades of brown fur, they are very difficult to tell apart.
They are also difficult to catch, weighing so little that conventional small metal box traps are often not effective. We have to dig holes called “pitfall” traps instead. Most species live in remote areas, so it has been difficult to understand their diversity until now.
New mammal species awaiting discovery There are several reasons we are still discovering new mammals in Australia. First, many mammal species have suffered declining populations, and are now very difficult to find. Also, we are using more advanced technologies to help us tell mammals apart, including sophisticated genetic methods.
But over time, perhaps what has changed most is the amount of information we can draw on. Museum collections hold more than 200 years of specimens and data — an irreplaceable scientific record that helps us recognise species we may no longer detect in nature.
It was through studies of marsupial genetics we first realised the number of planigales in Australia was likely an underestimate. A small number of genetic samples we previously studied suggested there were probably undescribed species of planigales in Australia.
But we needed to gather more samples to work out exactly where they lived. To do this, we partnered with organisations that survey for mammals in remote Australia, such as Australian Wildlife Conservancy, and pored over museum collections for extra genetic samples.
This way, we gathered hundreds of genetic samples of planigales and were finally able to work out if there were more species in this group. A planigale hiding among the rocks In 2017, a genetic study first identified a unique planigale found in Kakadu National Park, in the Northern Territory.
These results were based on only two genetic samples from preserved specimens held in the Museum and Art Gallery of the Northern Territory. We exhaustively checked more than 2000 planigale specimens held in Australian museums and found a single specimen that matched the existing two.
It was in the Queensland Museum, collected during the 1970s. These three planigale specimens, two males and one female, are genetically distinct from all other planigale species and have their own unique appearance. They are large (well, for a planigale) with dark grizzled fur and a very long tail – longer than other planigale species.
And they were found in an unusual location, on top of a rocky plateau. Most other species of planigales tend to live in swampy habitats, or areas with heavy clay soils. These factors confirmed we were dealing with a new species.
We described it [https://doi.org/10.1093/zoolinnean/zlag082] as the Arnhem plateau planigale, Planigale petrophila (meaning “rock-lover”). Since it is only known from three specimens, we urgently need to do more work to determine whether it is rare or under threat of extinction.
This is Planigale ‘petrophila’, the ‘rock lover’. Martin Armstrong But wait, there’s more And that’s not all.
During our study, we found specimens thought to represent a known species, Planigale ingrami, in the Kimberley region of Western Australia, were genetically distinct from those in the NT, Queensland and South Australia, even though they looked very similar.
This genetic information indicated these specimens were a “cryptic” species – something that can be identified by genetics but is difficult to tell apart based on appearance alone. By consulting historical research papers, we found these Kimberley planigales were in fact already described more than 100 years ago from a specimen collected in Australia that ended up in Sweden.
With help from curators at the Swedish Museum of Natural History, we were able to confirm this old specimen matched the new ones from the Western Australian Museum. We have called this the Kimberley planigale –Planigale subtilissima– as most of its range occurs in the Kimberley.
Unlike the Arnhem plateau planigale, Kimberley planigales have been detected frequently by Australian Wildlife Conservancy and partners on recent surveys, so there is less concern for their future. From five to nine species Our work has so far added four new species of planigales to Australia, as we had previously identified the orange-headed Pilbara planigale and the cracking-clay Pilbara planigale.
This has increased the diversity of this group of tiny mammals in Australia to eight species in total, with an extra one known in Papua New Guinea. It makes you wonder – how many more planigales and other mammals are out there waiting to be recognised?
This work would not have been possible without the help of my colleagues Linette Umbrello (WA Museum), Kenny Travouillon (WA Museum), Mike Westerman (La Trobe University), Mark Blacket (Agriculture Victoria), Skye Cameron (Australian Wildlife Conservancy) and Eridani Mulder (formerly Australian Wildlife Conservancy), and funding from the Australian Biological Resources Study and the Queensland University of Technology.
Andrew M.
Baker has received funding from the Australian Biological Resources Study (ABRS) and the Australian government.
Original source: https://analysis1.mil-osi.com/2026/06/24/we-checked-2000-museum-specimens-and-discovered-a-tiny-new-ferocious-australian-mammal/