Marsupial mole

Lore & Background

Marsupial moles spend most of their time underground, surfacing only occasionally, probably after rains. They are functionally blind, with eyes reduced to vestigial lenses under the skin, and lack external ears, having only tiny holes hidden under thick hair. Their head is cone-shaped with a leathery muzzle shield, the body is tubular, and the tail is a short, bald stub encased in leathery skin. They are uniformly covered in short, fine pale cream to white hair with an iridescent golden sheen. Their pouch is small, backward-facing to avoid filling with sand, and contains only two teats, limiting them to two young at a time. The limbs are very short with reduced digits. The forefeet have two greatly enlarged, spade-shaped flat claws on the third and fourth digits used for excavating soil, while the hindfeet are flattened with three small claws to push soil behind. Epipubic bones are present but small, and the last five cervical vertebrae are fused, giving the head rigidity during digging. The animal swims through soil and does not leave permanent burrows. Their teeth are degenerate and variable, with a dental formula of I 4/3, C 1/1, P 2/2, M 4/4 × 2 = 42; upper molars are triangular and zalambdodont, and lower molars appear to have lost their talonid basins.

Reader's Guide

Marsupial moles are significant as a striking example of convergent evolution, having independently evolved a body plan and digging behavior similar to placental golden moles and true moles, despite being marsupials. Their specialized anatomy—including reduced eyes, backward-facing pouch, fused cervical vertebrae, and enlarged foreclaws—illustrates adaptation to a fossorial lifestyle. The fossil record, represented by early Miocene Naraboryctes from Riversleigh, Queensland, shows a mosaic acquisition of dental and skeletal features from a more surface-dwelling ancestor, and demonstrates that the primary cusp of the molars is the metacone, distinct from the paracone of zalambdodont tenrecs and golden moles. Phylogenetic analyses consistently place Notoryctes as the sister taxon to a dasyuromorph-peramelian clade within Australidelphia, confirming its marsupial identity. The species are known by Indigenous names: the southern marsupial mole is called itjaritjari by the Pitjantjatjara and Yankunytjatjara people, and the northern marsupial mole is called kakarratul. Their conservation status and ecological requirements remain areas of ongoing research.

Did You Know?

• Marsupial moles do not possess a true cloaca; unlike monotremes, marsupials have separate openings.
• They are testicond, a condition also found in koalas and wombats.
• Their pouch faces backwards so it does not fill with sand while digging.
• The fossil notoryctid from early Miocene Riversleigh, often referred to as Notoryctes or a related form, shows a mosaic acquisition of dental and skeletal features from a more surface-dwelling ancestor.

The Accidental Discovery That Confounded Science

For thousands of years, Aboriginal Australians in the western central deserts knew this small, mole-like creature intimately, calling it the itjaritjari or itjari-itjari. A stockman named W. Coulthard, working on the Idracowra Pastoral Lease in the Northern Territory, noticed unusual prints in the sand and followed them to the animal lying beneath a tussock. Unsure what to do with the strange creature, he wrapped it in a kerosene-soaked rag, placed it in a revolver cartridge box, and forwarded it to E. C. Stirling, director of the South Australian Museum. The specimen arrived badly decomposed. Stirling could find no pouch or epipubic bones and declared the animal not a marsupial. The misidentification gained traction because nineteenth-century researchers were searching for a living missing link between marsupials and eutherians, and the creature's resemblance to Africa's golden moles led some to claim a cross-continental kinship. Better-preserved specimens later revealed a clear marsupial pouch, and the true story emerged: the similarities were the result of convergent evolution, not shared ancestry.

A Lineage Older Than the Deserts

The fossil record for the family Notoryctidae is sparse, yet it holds a remarkable clue. In the early Miocene sediments of the Riversleigh deposit in northern Australia, paleontologists identified at least one distinct genus, Naraboryctes, suggesting the lineage stretches back millions of years. Molecular studies have clarified what morphology alone could not: notoryctids are not closely related to any other marsupial family and warrant their own order, Notoryctemorphia. This order split from other marsupials roughly 64 million years ago, a time when South America, Antarctica, and Australia were still physically joined. From that point, the lineage evolved in Australia for at least forty to fifty million years. The Riversleigh material indicates that Notoryctes was already well adapted for burrowing and likely inhabited the rainforests that once blanketed much of the continent. The great increase in aridity at the close of the Tertiary period is thought to have been a key driver shaping the highly specialized form we see today. In other words, the marsupial mole had been tunneling long before the Australian deserts came into being.

A Body Built for the Dark

Its short, dense, silky fur ranges from pale cream to white, often taking on a reddish chestnut tint from iron oxides in the soil. The cone-shaped head flows directly into the body with no discernible neck, and the limbs are short but powerful, with digits three and four bearing large spade-like claws. There are no external eyes and no optic nerve; only a pigment layer where a retina once might have been remains. The dorsal rostrum and the back of the tail are bare and heavily keratinized. The external ear openings are buried in fur with no pinnae, and the nostrils are tiny vertical slits beneath a shield-like snout. Despite the brain being described as the lowliest marsupial brain, the olfactory bulbs and tubercula olfactoria are exceptionally well developed, reflecting a life in which smell replaces sight. The middle ear is tuned for low-frequency sounds.

Convergent Cousins and Desert Paradoxes

The southern marsupial mole bears a striking resemblance to the Namib Desert golden mole, Eremitalpa granti namibensis, and other specialized fossorial animals, yet this similarity is purely convergent. Like its distant African counterpart, it maintains a low and unstable body temperature ranging from 15 to 30 degrees Celsius. Its resting metabolic rate is not unusually low, but the metabolic cost of burrowing is sixty times greater than that of walking or running. Because it lives underground, where temperatures are considerably cooler than at the surface, the mole appears to lack any special physiological adaptations for desert survival. It is not even confirmed whether it drinks water; given the extreme irregularity of rainfall in its range, researchers assume it does not. Its habitat is restricted to soft sandy dunes and flats, typically where spinifex grass grows, spanning the central sandy deserts of Western Australia, northern South Australia, the Northern Territory, and the Great Victoria and Gibson Deserts. It feeds on earthworms and larvae.