Quokka-sized fossil species show for the fourth time that kangaroos have evolved to eat leaves.

Two new fossil kangaroos from the Riversleigh World Heritage Area (Queensland), Gumardee webbi (top) and Gumardee keari (bottom), their fossil skulls and jaws (left) and reconstruction (right).Credits: Reconstructed by Nellie Pease, provided by author

Kangaroos are so fond of leaves that the discovery of new fossils has revealed that their ability to eat leaves has evolved at least four times in their evolutionary history.

There are over 60 today Race A herd of kangaroos, wallabies, betons, and rat kangaroos that live throughout Australia and New Guinea.But their diversity is time Even more incredible. Just 100,000 years ago, Australia had many species of giant kangaroos. It contained, strangely, a giant short-faced kangaroo that did not jump and instead walked like a theropod dinosaur such as Velociraptor.

Going back further, until about 20 million years ago, there were many more interesting kangaroos. Some of them were the direct ancestors of today’s species. In general, these seeds were not larger than wallabies, but they were very diverse, including kangaroos with fangs and kangaroos that could eat meat.

We know all this, thanks to the amazing fossils found in the Riversley World Heritage Site in northwestern Queensland. Probably the most famous fossil location in Australia. So far, about 30 species of prehistoric kangaroos have been found here. And the two recently discovered add another interesting twist to the evolutionary story.

Our latest discoveries, Released todayNames two new species of ancient kangaroos. Gumardee webbi and Gumardee keari co-existed in the Riversley rainforest about 18 million years ago.

They are represented by some partial skulls and some jaws and tell us a lot about the biology of these extinct animals.

Each of these kangaroos weighs 3-4 kilograms, approximately the size of a quokka. But what is most intriguing about them is their teeth. The molar blade pattern is perfect for eating trees and bush leaves. This is amazing. Because their ancestor, Gumaldee springae, who lived in the same place about 6 million years ago, had teeth that were better suited to a wide range of foods such as fruits, fungi and insects.

two Previously discovered species, Gumardeepascuali and Gumardeerichi were between these two groups in terms of both evolutionary age and tooth patterns. This means that the fossils of Riversley come together to reveal the evolutionary process by which kangaroo teeth change and adapt to a variety of foods.

Leaf taste

Surprisingly, this is not the first time this has happened in a kangaroo fossil record. From the late 1990s to the early 2000s, the late paleontologist Bernie Cook studied Riversley’s kangaroos in detail. discovered The ancestors of modern kangaroos are generalists, mainly eating forest fruits, fungi and insects, and slowly evolving their ability to eat leaves over time.

Today, kangaroos and wallabies eat only bushes and leaves, while rat kangaroos, betons, and potrues eat fungi, fruits, and insects, just like ancient kangaroos.

He is another family of ancient kangaroos in Riversley, Kangaroo fangsIndependently evolved the same ability to eat leaves at about the same time.

A fossil site in South Australia also confirmed another independent evolution of eating leaves. Third documented instance In a kangaroo.

Therefore, the two new species found in Riversley represent the fourth occurrence of leaf-eating. Kangaroo Fossil record.

Competition in the rainforest

Only one of these four groups (Riversleigh species studied by Cook) is the direct evolutionary ancestor of today’s kangaroos and wallabies. All three other groups that pioneered eating leaves eventually disappeared. A South Australian species about 23 million years ago. The Gumaldi Group about 15 million years ago. And a kangaroo with fangs about 10 million years ago.

The obvious questions that arise are: Why have all these groups disappeared? Does this mean that today’s kangaroos and wallabies have evolved to eat dangerous and highly specialized diets?

I know their ancestors ate fruits, fungi and insects, but so did many other marsupials, such as bandicoot and possums. In fact, many of these various marsupial competitors are evolutionary because ancient kangaroos diverge into leaves that were available all year round in contrast to other foods, especially seasonal fruits. It would make sense.

So why didn’t they survive? At that time, they were not the only ones who evolved their ability to eat leaves. The competition was fierce as it happened in Possums, Koalas and Wombats.

We have always known that Australia is a difficult place to survive.Australia’s Over 10 Million Years of Riversley Fossil Evolutionary historyShows how hard it was.

The little kangaroos that couldn’t jump lived longer than their fan’s cousins

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Quokka-sized fossil species show for the fourth time that kangaroos have evolved to eat leaves.

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