Millions of years ago some kangaroos had viciously long canine teeth, at least relative to their small size. Discoveries at the famed Riversleigh World Heritage area in Australia reveal less time separates us from these fearsome fangs than we thought, although we still don't really know what they were for since their owners were just as herbivorous as their modern equivalents.
The kangaroo family appears an exception to the claim that “everything in Australia is trying to kill you”. Sure the larger members can deliver a vicious kick, but mostly they're friendly live-and-let-live types. However, they once shared the continent with relatives called balbarids, large-fanged members of the same superfamily.
Palaeontologists are interested in the parallel evolution of the two kangaroo families, and why the fanged version eventually went extinct. Ideally, this might teach us something about dangers to modern-day kangaroos, 21 of which are endangered or vulnerable.
Kaylene Butler, a PhD student at the University of Queensland, said in a statement; “Currently, we can only hypothesize as to why balbarids became extinct – the original hypothesis related to events during a change in climate 15 million years ago.” Butler has punctured that theory by announcing in Palaeogeography, Palaeoclimatology, Palaeoecology the discovery of balbarid specimens from 10 million years ago – 5 million years after the events thought to have caused their extinction.
Since North Queensland didn't have climatic shifts 10 million years ago like the ones 5 million years earlier, the question of what caused the balbarid extinction remains unresolved. Since fangless kangaroos appear to have occupied a similar ecological niche, one possibility is that they became better adapted than their fanged cousins, driving the balbarids out.
Butler told IFLScience that balbarids and modern kangaroos shared a common ancestor. Unfortunately, there's a gap in the Australian fossil record, sometimes known as the fossil dark ages, around the time this occurred, so we don't know what this common ancestor was like. When the fossil record resumes, tiny (around 1 kilogram or 2 pounds) fanged and fangless kangaroos are found. Over the following 15 million years, both grew to around 12 kilograms (26 pounds) before the balbarids disappeared.
The fangs' purpose remains a mystery. Butler explained to IFLScience that we have insufficient fully intact skulls to determine whether the males possessed larger fangs than the females, suggesting they were used for mating displays and fights, like in modern musk deer. Alternatively, they may have been predator defenses or for digging in the dirt for fungi.
Perhaps if they had survived, the balbarids would have grown to the size of modern red kangaroos – or even their giant ice age predecessors, making the continent even more intimidating.