Fossils show that ancient marsupial lions tore apart the wallabies in Australia – roll on Saturday
As the British and Irish Lions continue to tackle the Wallabies in the current rugby tour, it should be remembered that this is not the first time that lions have been dismembering wallabies down under.
Some recent research of Pleistocene Era fossils from Australia has described some superb fossil beds that contain the remains of numerous animals and their footprints. As the kinds of sediments that preserve tracks are typically different to those that preserve bones, we tend to find either fossil skeletons or trackways, but rarely both, so this is already an unusual occurrence. It also means that palaeontologists have a better chance of correctly assigning tracks to individual species since they have a good idea of what is around and it means they can see what is showing up in tracks that isn't in the skeletal fossils and vice versa, and so examine biases in preservation. Best of all though, more than 70 bones show bite marks that indicate which carnivores were feeding on them.
A great number of the bones belong to animals of the genus Macropus, the group that includes kangaroos and wallabies, and at least some of the bites can be attributed to Thylacoleo, the 'marsupial lion'. Lions really were eating wallabies. Probably. Ok, so it's a slight cheat because while there are definitively bites from Thylacoleo there, and there are small Macropus present (which might well be wallabies) there's no specific claim of a bite from a marsupial lion on a wallaby bone since identifications of broken bones and of course exact identifications of original 'biters' are hard to do.
And of course, the lions are another marsupial, rather than a true lion or even member of the cat group, but the term 'marsupial lion' really is the common name for Thylacoleo, and it really was somewhat lion-like. Indeed, it is one of quite a few marsupial animals that resembles more familiar mammals and thus is a perfect opportunity for me to bring up convergent evolution.
Convergence is where organisms under similar evolutionary pressures tend to evolve similar forms. So swimming animals tend to have hydrodynamic shapes (tuna, penguins and dolphins say) and ant-eating animals have large claws, strong arms and long snouts with no teeth (aardvarks and anteaters). The important point of convergence is that the species in question are relatively unrelated, such that the acquisition of these characters is independent. Tuna, dolphins and penguins (and indeed icthyosaurs) are all vertebrates, but although the ancestors of tuna were fish and probably already that shape, all the others are descended from terrestrial, four-legged ancestors and each convergently evolved the same general body plan.
In the case of Australia, the majority of their native mammalian fauna are marsupials (the numerous bats being the most obvious exception) and with ecological niches to be filled, many animals evolved similar forms to those mammals in the rest of the world. Living examples include marsupial moles and marsupial mice that are rather like the 'normal' versions, sugar gliders are analogous to flying squirrels and the numbat is a marsupial anteater. This extends to extinct forms too, with the Tasmanian wolf (also known as the Tasmanian tiger or thylacine, though it was also on the mainland too) being close in appearance to a coyote or fox, and Thylacoleo to a lion.
There were several species of Thylacoleo and the larger ones were over 100 kg, so these were big predators. Like cats they had evolved retractable claws and their teeth, while odd by the standards of normal mammals, include both stabbing, killing teeth and those to cut up their prey. Their overall form was that of a very stocky cat and they were the largest and most dangerous predators in Australia at the time and would have been a serious threat to humans. Clearly they were a threat to the Macropus animals of the era and killed and consumed them.
Let's see (hope) if history repeats itself in the next test.
On a more serious note, I would like to apologise to Camens & Carey for somewhat trivialising an excellent and interesting paper in order to take a cheap shot at a rugby team, and also to friends, colleagues and readers in Australia for the same reason. But well, when you come across something this good, it would be a waste not to use it and if being a fan of a sport doesn't permit you to take cheap potshots at the opposition then an awful lot of us would have much more time on our hands. May the best team win etc, though I'll be behind the red side of the equation tomorrow.