You only live twice

Australia is a continent full of weird wonders. From kangaroos to koalas, the animals here are unlike anywhere else on the planet. Australia is a landmass that has drifted slowly northwards, alone, across the empty Indian Ocean for over 30 million years. After it ripped apart from Antarctica, it carried with it a small cargo of mammals that evolved and adapted to life on this huge drifting land. Unlike most other parts of the world, marsupials here thrived. These hairy, milk producing mammals differ from you or I as their young are born very early and develop in a pouch. (We are placental mammals, like cows, whales and mice, where our babies develop fully inside the mother). In other parts of the world, placental mammals outcompeted marsupial mammals: they produced more young at a quicker rate. A hundred species of marsupials cling on in South America, Central America and in the very south of North America. But with over 330 species in Australia, it is here that is the home of the marsupial. Before the arrival of Europeans, there were very few endemic placental mammals (some bats, bush rats and hopping mice): all inconspicuous under the feet of the successful marsupials.

The iconic marsupial, the kangaroo. Notice the youngster in the pouch, which can develop and grow there for (Image Public Domain)

Isolated for so long, without the competition of placental mammals, marsupials evolved into some of the most wondrous, strange animals to have walked our planet. Enormous wombats the size of a car, giant kangaroos, and deadly hunters like the marsupial lion owned the land. What an incredible sight they must have been for those first people to explore the land 50,000 years ago!

There were even weirder creatures too. Like our beast, Palorchestes, which may well have been one of the strangest of the Australian megafauna.

For over 70 years this was thought to be something it wasn’t: a creature with a fake identity. This fairly large mistake was due to the problems palaeontologists face when there are new finds. It’s not an easy task. Sometimes we get pretty complete skeletons which makes it a lot easier to compare to other living and extinct animals. Most of the time the bones are small, broken, or crushed. There are thousands of unknown animals lying in drawers in museums: parts of them that have survived erosion, scavenging, or trampling, waiting patiently for their identity to be revealed. They have waited millennia, a few more years won’t hurt them.

The well-known, egocentric Victorian scientist Richard Owen described this beast based on one fragmentary jaw. The teeth looked similar to those of a kangaroo, so he named it Palorchestes – the ‘ancient leaper’. He gave this extinct animal a name, but it would be decades until this creature’s true identity would be revealed.

For a while this animal lived as a kangaroo in the scientific world. More fossils were found of this Australian giant, and in the 1950s it was identified as a new family of marsupials, named Palorchestidae. The giant kangaroo was no more: it was born again as a new type of creature, closely related to the enormous wombats Diprotodon and Zygomaturus (belonging in the Order Diprotrotodontia). This new family includes four different genera, with only 8 species. (Taxonomy can be a bit of a headache at times. We humans are classed in the Order of Primates – along with all apes and monkeys – and we are in the Family Hominidae. There are dozens of different genera of Hominidae, most of which are now extinct. Today the family just has 8 living species including chimps, gorillas, orangutans and humans: we are in the genus Homo.)

The big, weird giant Palorchestes azeal.

This strange, small family of marsupials were extremely longed lived. Evolving in the Miocene around 11 million years ago, they possibly survived until around 40,000 years ago. It appears that there was not much overlap with different species of Palorchestes living at the same time, with the fossils suggesting that species progressively for larger through time: the largest was P. azeal.

(This view of species evolving straight into another species is often misleading. It implies that one evolved straight into another, with just that one species living on the planet. In reality, a population of one species evolved locally adapting to changes, while other populations continued to live for millennia in other parts of Australia before becoming extinct. Reading the rocks from a fossil site may show one species replacing another, whereas in other parts of the continent that extinct species was likely around for longer. The fossil record is incredibly amazing because it allows us to know more about life in the past. But it is also incredibly frustrating because we need more fossils to paint a clearer picture of what was happening.)

This beast was widely distributed across Australia and Tasmania. Fossils are not very common suggesting it was a solitary animal, similar in lifestyle to rhinos and sloths. It was utterly bizarre. Its odd skull with short bones in the nose, hints that it had a short trunk, not too dissimilar to a tapir, giving it a more common name of marsupial tapir. Structures in the lower jaw indicate a long, thick, muscular tongue. With robust front limbs with pretty big claws, and a kangaroo-like tail, our leaping marsupial was no leaper.

This strange anatomy provides clues to the lifestyle of the marsupial tapir. The consensus is that Palorchestes was a solitary, browsing animal, living in open woodlands, using the claws to pull down branches and that thick, long tongue to pluck off leaves. The claws would have been used for defence and may even have been used to dig for roots. I wonder if there was more to it than that. The giant sloths and giant armadillos in North America had huge claws, and lived in similar habitats. There is evidence in South America that some dug massive burrows. The powerful forelimbs and strong claws could have been used in a similar way for Palorchestes, providing shelter from predators and a safe way to bring up their young. As yet no huge palaeo-burrows have been found in Australia, but I like to think that one day they might be.

With so few fossils of Palorchestes, it is unclear exactly when this species became extinct.  To date there have been no fossils found indicating that humans hunted or ate them. The youngest concrete dated specimens are around 100, 000 years ago, which is a good 60,000 years off the main mega-faunal extinctions in Australia. Some fossils have been radiocarbon dated giving much younger dates, but the samples have included lots of contamination or degraded too much for the dates to be reliable.

However, there is tantalising evidence that early inhabitants of Australia may have even seen these animals.

40,000 years ago someone painted some animals on a cave wall. Is this a painting of the marsupial tapir? (Image from Oakes 2003)

There are several cave paintings in Arnhem Land, with one that has been thought to be of the marsupial tapir. This painting dates to around 40,000 years old, long after the last radiocarbon dated specimen. Perhaps this is not Palorchestes. Perhaps it is. Fossils of this creature are quite rare, and we must remember that the last radiocarbon dated individual does not represent the last individual of that species. It would be strange that it disappeared long before the other Australian giants. But then the climate in Australia was becoming dried in the Late Pleistocene, reducing the wet rainforests and woodlands. More sites with more fossils will give us more answers.

This remarkable animal has perplexed us since it was first discovered. It has lived two lives since the late 1800s, and it still have many secrets to reveal.

Written by Jan Freedman (@JanFreedman)

Thanks to Gilbert Price (@The FatWombat) his comments on the post.

Further reading:

Anderson, C. (1933) ‘The fossil mammals of Australia.’ Proceedings of the Linnean Society of New South Wales. 59. pp.ix-xxv.

Archer, M., Hand, S. J., & Godthelp, H. 1994. ‘Riversleigh: The story of Animals in Ancient Rainforests of Inland Australia.’ Reed Books, Chatswood. [Book]

Banks, M. R. Colhoun, E. A., & van den Geer, G. (1976) ‘Late Quaternary Palorchestes azeal (Mammalia, Diprotodontidae) from northwest Tasmania.’ Alcheringa. 1(2). pp.159-166. [Full article]

Black, K., & Mackness, B. (1999) ‘Diversity and relationships of diprotodontoid marsupials.’ Australian Mammalogy. 21. pp.34-45. [Full article]

Long, J., Archer, M., Flannery, T., & Hand, S. J. (2002). ‘Prehistoric Mammals of Australia and New Guinea: One hundred million years of evolution.’ Kensington. University of South Wales. [Book]

Martin, P. & Klein, R. G. (Eds) (1989) Quaternary Extinctions. University of Arizona Press. [Book]

Oakes, T. (2003) Monsters we met. BBC Books. [Book]

Owen, R. (1873) ‘On the fossil mammals of Australia. Part IX. Family Macropodidae: Genus Macropus, Pachysaigon, Leptosaigon, Procoptodon, and Palorchestes.’ Phil Trans Roy Soc. 164. pp.783-803.

Price, G. J., Feng, Y., Zhao, J., & Webb, G. E. (2013) ‘Direct U-Th dating of vertebrate fossils with minimum sampling destruction and application to museum specimens.’ Quaternary Geochronology. 18. pp.1-8. [Abstract only]

 

This entry was posted in Diprotodon, Giant Short-Faced Kangaroo, Marsupial Tapir, Zygomaturus and tagged , , , , , , , , , , , , . Bookmark the permalink.

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