Procoptodon goliah (right), the largest known species of kangaroo, weighed in at about 200kg and would have towered over the largest species today, the red kangaroo (below). It could reach branches up to 3m from the ground. Studies of fossil remains have
f lesh. Weighing in at 80kg, this would have been a truly fearsome beast. Its opposable thumbs, tipped with enormous sheathed claws, suggest it was also able to climb trees, and was likely to have been an ambush predator.
Birds were numerous and varied, including giant megapodes (the group the modern malleefowl and brush turkey belong to) and coucals (large, ground-based cuckoos) as well as a host of parrots, ducks, waders, owls and raptor species that still inhabit Australia today. The fact that parrots nest in tree hollows is further evidence that the prehistoric Nullarbor was far from treeless.
Among the trees of this unfamiliar landscape you would also have seen many species you may know well, for not all are extinct, and still survive and prosper today. Many have now retreated from the plain or cling on in remnant vegetation around its fringes.
Extant species of possums, bandicoots, kangaroos and wallabies, wombats, bats, lizards and snakes, quolls, devils, bettongs, small carnivores such as antechinuses and mulgaras, rodents such as the delightful and impossibly cute hopping mice, and birds, were all thriving on the Nullarbor 500,000 years ago.
This diverse range of creatures with differing habitat and dietary requirements also points to an equally expan- sive range of f lora, which must have been considerably more varied than what can be seen on the plain today.
But I have left until last the most surprising creatures found in the caves, that most accurately represent the enormous environmental changes that have occurred in the region. After many months of sorting through an immense pile of small animal bones, palaeontologists uncovered the remains of three frog species, the f irst frogs, living or fossil, to have ever been documented on the Nullarbor. That frogs could live on the plain seems inconceivable. One species, the common spadefoot toad
Among the trees of this unfamiliar landscape you would also have seen many species you may know well, for not all are extinct.
( Neobatrachus sudelli), remains widespread, and may still turn out to occur there today. It is perfectly adapted to an arid environment, and was found in both early and mid-Pleistocene sediments.
Two species discovered on the prehistoric Nullarbor – a green tree frog and a toadlet – would have inhabited seasonally moist conditions, and needed transient pools to breed. These animals were found in the lower levels of the excavation from the early Pleistocene, about 1 million years and up to 2.5 million years ago. One of these two species ( Litoria lundeliusi) was new to science.
THE NULLARBOR TODAY is certainly an impoverished landscape. Long gone is the diverse community of trees, shrubs and grasses. Sometime in the late Pleistocene something happened that changed the vegetation forever, and along with that change came the loss of the rich diversity of animals that depended upon it. The Nullarbor’s Pleistocene f lora and fauna evolved to cope with the climate cycles that followed and the slow march to ever-increasing aridity.
Most palaeontologists would agree that it was not climate alone that brought about their demise. Some suspect that the hunting of the larger mammals by humans after they arrived in the area about 50,000 years ago, and perhaps also their use of f ire in the landscape, was inf luential. Although not all of the now extinct species survived into the late Pleistocene, some certainly did, and evidence from other sites shows a period of overlap with human arrival.
The most recent biological survey was undertaken in 1984 and lists the f lora and fauna known to be extant on the Nullarbor at European colonisation 200 years ago. By that time all the large herbivores, apart from the red kangaroo, had already long gone, along with their fearsome carnivorous predators.
Much of the fossil material that has been recovered from the Nullarbor so far has yet to be identif ied, and there are other caves that remain to be explored. It’s likely that many more ghosts may haunt the passages and chambers beneath the endless landscape of the Nullarbor, wandering forever among the trees of an ecosystem never to be seen again.
SUSAN DOUBLE AND AUSTRALIAN GEOGRAPHIC would like to thank Professor Gavin Prideaux for his expert input into this article and Sam Arman and Grant Gully for their assistance with the images.
Spadefoot toad fossils have been found in the Nullarbor’s caves. The species may still be present on the plain today, as yet unseen, because it can remain buried for many years awaiting rain.
Cavers Eve Taylor and Dan Searle prepare to abseil down through the tiny entrance into LBC during an expedition shortly after its discovery.