A diprotodontid with bizarrely wide cheekbones. Possiblyfor display or weaponry; its face was unlike any living animal.
Nobu Tamura, CC BY-SA 4.0, via Wikimedia Commons
A Pliocene Giant
During the Pliocene Epoch, between 5.3 and 2.6 million years ago, much of Australia was a warmer, wetter place than it is today. In the woodlands and forests of what is now Queensland and New South Wales lived a giant marsupial called Euryzygoma dunense. This herbivore was a large animal, reaching about 2.5 meters in length and weighing an estimated 500 kilograms. It belonged to the family Diprotodontidae, it was a relative of the largest known marsupial, Diprotodon, and more distantly related to modern wombats and koalas.
Euryzygoma was a browser, feeding on leaves and shrubs. Isotope analysis of its fossil teeth confirms it preferred C3 plants, which are typical of forests and cooler, wetter environments. It shared its habitat with other megafauna, including giant kangaroos, the earliest known quolls, and even Komodo dragons, which originated in Australia before migrating to Indonesia. The first fossils of Euryzygoma were identified from isolated teeth, but a more complete skull was unearthed in 1912 by workers digging a well on the Darling Downs in southeastern Queensland.
A Skull Wider Than Long
The most extraordinary feature of Euryzygoma is its skull, which was wider than it was long, a rare characteristic among mammals. This extreme width comes from enormous, flange-like extensions of the zygomatic arches, or cheekbones. The name Euryzygoma itself translates to "broad cheekbone." Paleontologists have several theories about the function of these bizarre structures.
One idea is that the flanges supported large, fleshy cheek pouches for food storage. This would have allowed the animal to gather large quantities of vegetation quickly and retreat to a safer location to chew its food, perhaps reducing its time spent at dangerous, crocodile-infested waterholes.
Another theory suggests the cheekbones were for sexual display. Not all Euryzygoma skulls have equally developed flanges, which indicates sexual dimorphism, a distinct difference in appearance between males and females. Wider-cheeked individuals were likely males, using their impressive headgear to attract mates or intimidate rivals, like the antlers of a moose. These bony extensions might also have been used directly in combat between males. The bone at the end of the flanges is smooth, suggesting they were covered in skin, not horn-like growths.
💡Fun Facts
The name *Euryzygoma* literally means "broad cheekbone," directly referencing its most distinct feature.
Some male skulls were so wide that they measured more across the cheekbones than from the snout to the back of the head.
This animal is believed to be the direct ancestor of *Diprotodon*, the largest marsupial that ever lived.
The first significant skull of *Euryzygoma* was discovered by accident in 1912 by men digging a well near Brigalow, Queensland.
