Australia: The Land Where Time Began

A biography of the Australian continent 

The caves are 8 km south of the town of Wellington. The fossil bearing deposits, that the caves were cut into, are in the limestone of the Garra Formation, dated to 360 million years ago in the Devonian. This formation was a tropical coral reef with a rich and varied fauna. The fossils that were of so much interest to the scientists of the 1800s are the Big Sink Fauna, found only in the Big Sink cave, from the Early to Middle Pliocene, about 4 million years old. The fossils here were mostly small animals such as marsupial mice, ringtail and pygmy possums, and extinct kangaroos. There were also some marsupial lions and thylacines.

The vertebrate fossils forming a vast majority of those found at the site were of animals that had fallen into the caves after they had cur through the Devonian limestone during late million years of the Pleistocene. These fossils are found in several of the caves and the phosphate mine that was dug into the site.

The Wellington Valley is south of Dubbo and north of Orange, in New South Wales. The caves consist mostly of deep vertical shafts, which is one reason so many animals fell into them. The largest known stalactite in the Southern Hemisphere is one of the caves. The caves have been known to the settlers since 1826 or 1827. They are the site where the first significant find of vertebrates in Australia, and the first vertebrate deposits to be excavated systematically, which have continued for the past 170 years. It was the place where the first evidence was found that the prehistory of Australia differed from that everywhere else in the world. Augustus Earl, an artist from the Beagle painted several watercolours of the caves when the Beagle visited Sydney, making a special trip to see them. The first fossils from the caves were announced in 1830 and the first specimens had been sent to Prof Robert Jameson in Edinburgh. The fossils from the caves were soon doing the rounds of the scientific elite in Europe and Britain, who were so interested in them that they pressured the Australian governments to put money into vertebrate palaeontology. Such leading lights in the scientific world as Jameson, Buckland, Owen and Curvier all studied the fossils and were convinced they were unique, similar to living animals in Australia, and like animals nowhere else in the world.

At the time debate was raging about fossils being the animals drowned in Noah's flood and the Wellington Caves fossils proved to be a fly in the ointment for such a theory. Questions were asked about how such weird animals were present in the caves, they should have been the same as animals from elsewhere in the world that would have been washed into the caves by the floodwater. Richard Owen wrote to the New South Wales government urging them to pay for a systematised of the caves, which they did.

Monotremes

Among the animals found at Wellington Caves is Zaglossus, the giant echidna, that looked like large modern echidnas, but instead of ants it ate worms. There are 4 fossil species of Zalgossus, the only surviving species lives in the New Guinea rainforests. It is believed the genus became extinct in Austeralia about 20,000 years ago.

Carnivorous marsupials

Modern species found in the caves include the Tasmanian devil (Sarcophilus) and the Tasmanian tiger (Tasmanian wolf) (Thylacinus cynocephalus). The marsupial lion (Thylacoleo carnifex) may have been able to climb into the caves to scavenge then climb out again, but it is believed to have been a predator. Between a leopard and a lion in size, it's marsupial teeth had adapted to eat meat and the incisors developed into powerful cutting teeth that differ from the stabbing and shredding teeth of the modern big cats. It is been described as having bolt-cutter teeth that would probably have been capable of biting clean through bone. They also had sharp, curved retractable claws.

Herbivorous marsupials

One of the animals in the caves was the bilby (Macrotis lagotis). Until the spread of feral predators - cats, dogs and foxes - the bilby was widespread across Australia, but the ferals have brought it close to extinction, and it may yet be lost. There were also hairy-nosed wombats (Lasiorhinus kreftii), another animal nearing extinction. Other wombats found in the caves are the common wombat (Vombatus ursinus), that is still extant, but 2 others are now extinct, Ramsayia and Phascolomys.

Diprodontids are represented in the Wellington Caves by 2 species of Diprotodon. They are not in the same group as wombats and looked more like a rhino without a horn than a big wombat. The bones of a Diprotodon were sent to Robert Jameson in Edinburgh and he thought at first he was looking at an elephant. The head of Diprotodon was 1 m long and had very large teeth. It was a browser.

There were also fossils of Zygomaturus. This was a bit smaller than Diprotodon, and had prominent cheek bones and on its muzzle and forehead that are believed to possibly have been the bases of horns. During the Pleistocene it seems to have had a different distribution from Diprotodon, being mostly found around the edges of the continent while Diprotodon was found mostly in the central areas. Wellington Caves is rare in that it is one of a few sites where Diprotodon and Zyomaturus are found in the same deposit.

Palorchestes, related to Diprotodon, it had the appearance of a marsupial bear. When the teeth of Palorchestes were first examined it was believed they were from a giant kangaroo, only being recognised for what they were when more complete remains were found. It was a herbivore but had powerful long, curved, claws and its front legs were longer and better developed than its hind legs. The bones of the front of the snout suggest it had a trunk. It is thought to have used its trunk, claws and strong front legs to pull branches down to feed on leaves.

Kangaroos

A living species, the rufous bettong (Aepypyrmnus refescens) was found in the cave deposits. These are one of the smaller macropods, weighing about 2 kg. Their muzzles are short and they have reddish grizzled fur around the back of the neck and shoulders. The living species is being pushed towards extinction, mostly by feral animals, that have added to the natural predators like dingos and eagles. Another was present in the Wellington Caves, Bettongia sp. Bettongs specialise in below-ground parts of plants, roots, tubers, truffles, etc.

Propleopus, the giant rat kangaroo, has also been found in the caves. It was of about the same size of a modern grey kangaroo, but of a much heavier build, probably weighing about 70 kg. Analysis of the bones and teeth indicate it was carnivorous. It is though the Aboriginal People might have arrived in Australia before Propleopus became extinct.

There was a wide variety of browsing kangaroos found in the cave deposits. Sthenurines are now almost extinct, but at the time the cave deposits were being laid down, during most of the Pleistocene, the diverse group were very common. Their characteristically short snout is believed to be an adaptation for browsing in the forest. There were 2 species of Procoptodon at the caves. Species of this genus could reach more than 2 m tall, making them by far the largest known kangaroos. One of the most common fossils found in the caves were 5 species of Sthenurus, they were also common in many other deposits dating to around the same time.

There were 2 species of Troposodon, thought to be a giant form of the extant banded hare-wallaby Lagorchestes leporides, which has also been found in the cave deposits. There is a controversial view that banded hare-wallaby may be the only extant sthenurine kangaroo. Lagorchestes weighed about 1 or 2 kg, whereas Troposodon is believed to have weighed as much as 50 kg.

There were 2 species of Protemnodon, macropodine kangaroos. The members of this macropodine group are mostly grazers. species of Protemnodon are among the most common kangaroos throughout Pleistocene Australia. One species, P. brehus, was a bit larger than largest of the extant kangaroos. A single species rock wallaby and 1 species of pademelon have been found in the caves.

The forests around the area of the caves supported 10 types of browsing (leaf-eating) kangaroos that ranged from the size of a rabbit to that of a horse. As well as these browsers there were some grazers (grass-eaters), that indicated there must have been some grassland as well as the forest inhabited by the browsers. These grazers were the macropodines, a group that includes most extant kangaroos and wallabies. There were 4 species of Macropus, some members of which are the living red and grey kangaroos, as well as some other extant species. These included the living species, the agile wallaby (Macropus agilis) and the extinct M. titan, and extinct form of the extant eastern grey kangaroo, that grew to about 10 % larger than its modern relative. Nailtail wallaby species were also present in the caves.

The discovery of Bohra was unexpected. It was related to living tree kangaroos, but was between 20 and 30 % larger. It appears that Bohra lived in the more open forests of the Wellington Caves area. The living tree kangaroos are restricted to the tropical rainforest.

Placentals

2 types of eutherian mammals occur in the cave deposits from the Pleistocene, bats and mice, several species of ach being present.

The ghost bat Macroderma gigas feed on small vertebrates that it takes back to its roost to eat. As a result of this feeding habit the remains of the small animals of the surrounding area have accumulated beneath the bat roosts.

Birds

Among the bird fossils from the cave sites are emus, falcons, crows, quails and songbirds. There were also several different types of dromornithids. 2 species of mallee fowl have been found in the deposits. There was a masked owl that probably roosted in the caves, it has been suggested that the remains of the small birds may have been its prey brought to the cave, the bones being the regurgitated. Modern masked owl usually roost in hollow trees.

Reptiles

Among the reptiles found at the caves are a turtle and a dragon, 3 different goannas and shingleback lizard. One of the monitors, Megalania, was no ordinary goanna, being 5 m or more long. There were also a very large snake, Wamambi, about 6 m or more long.

• Fossil Sites
• Marsupials