Tracking the evolutionary history of our once carnivorous bilbies and bandicoots
IN HIS MOST recent paper, which now features on the cover of the 2017 addition of the Journal of Vertebrate Palaeontology, mammologist Kenny Travouillon has identified two new species of ancient bandicoot. And while he admits he finds this exciting, he wouldn’t agree that these are the most important revelations to come out of his research.
“While discovering new species and naming then is quite rewarding, I think the most important finding is to document what happened to species in the past, so we can use that information for the future,” Kenny says. “Climate change is real, and it most certainly will affect many species around the world, but we don’t always know how they will be affected.”
Piecing together the puzzle
In order to fill in the gaps in the evolution of bilbies and bandicoots, Kenny began collating all the fossil material of these unique Australian animals from the Pliocene epoch, which occurred 5 to 2.5 million years ago.
Previously, Kenny had worked on much older fossils dating back 26 to 10 million years ago; mostly from Riversleigh in north-western Queensland, so fossils records from the Pliocene were an important piece of the puzzle.
“I started to analyse how these new species were related to older species from Riversleigh, and to the modern bilbies and bandicoots. Then, as the pieces of the puzzle come in place, it becomes much easier to interpret what really happened through time.”
Kenny and a host of other researchers have successfully identified all the potential ancestors to the modern bilbies and bandicoots, as well as an ancient group of bandicoots that went extinct as a result of habitat loss.
According to Kenny, during the Pliocene the ancient ancestors of these marsupials are present in the rainforests of Victoria and New South Wales, but by the Pleistocene epoch, which occurred 2.5 million to 12,000 years ago, they are absent in these states, and only present in one rainforest patch in Queensland.
By the late Pleistocene these ancestors are non-existent in the fossil record, “so it is becoming quite clear that they are disappearing with loss of rainforest,” Kenny says, adding that this information may have an impact on the direction of conservation efforts.
“Perhaps we should focus more on the conservation of habitats, especially habitats that are likely to disappear as a result of future climate change.”
Kenny says that the evolution of these Aussie marsupials is long and complicated, with many climate casualties along the way.
“Between 26 and 10 million years ago, this group of marsupials was a lot more diverse, with many species of small insectivorous bandicoots, large carnivorous bandicoots, and large omnivorous bandicoots and bilbies, with the ability to dig. By the Pliocene, we lost carnivorous bandicoots.”
Other species of bilby and bandicoot were able to adapt.
“One of the features that is heavily influenced by climate change is the hearing ability of bandicoots and bilbies. Some bandicoots evolved larger ears, other evolved a larger bulla, a resonance chamber in the internal ear, and bilbies evolved both.
“The other feature is their teeth. As the vegetation becomes tougher, and they start ingesting more grit from the soil from the food they dug up, they start wearing their teeth down quickly.
“Some of the bandicoots have evolved teeth with higher crowns, so they last longer, while bilbies seem to do that and also have thicker enamel to make the teeth stronger.”
Reconstructing the past
To accompany the research, Kenny enlisted renowned palaeo-artist Peter Schouten to reconstruct these ancient animals.
“I have known of Peter’s work for many years. He has done some of the most magnificent reconstruction of fossil species to date, so I have always wanted to work with him on reconstructing the animals I work on,” he says.
While it sounds difficult to reconstruct these extinct animals — never seen by the human eye before —Kenny says it depends on the fossil record.
“If we have the complete skeleton, and some imprints of the skin, fur or feathers, then it is very easy to make an accurate reconstruction.
“Here, we only have jaws and teeth, so we are especially reliant of their closest modern relative to complete the body shape and fur colour of the animals.
“Giving the same limited information to two different palaeo-artists would result in two very different reconstructions, as the artist will have their creative input in the reconstruction.”