fossils

The little kangaroo that couldn't hop

3986b46bb4f35aa1ff4d42167a12e0fc

Vasika
Udurawane

Writer
34f1d64c52c45a6bdce31bc5e48b86cc

Julio
Lacerda

Staff Artist and Writer
We all love kangaroos for their athletic abilities, charm and charisma. Before you can hop though, you need to scurry. And there was one roo that did just that, more than 20 million years ago. It was small, innocuous and rat-like, and shared the ancient Australian forests with its bigger fanged cousins.

The fossil record of extinct kangaroos is incredible. Not only do we have the remains of heavily-built giant roos, we also have omnivorous and even predatory species of rat-kangaroo and smaller varieties no bigger than today’s smallest wallabies. This especially goes for some of the early species that were found all over Riversleigh, one of the most famous Australian fossil sites and a UNESCO World Heritage Site. The fossil site as a whole is made up of limestone deposits occurring in freshwater pools, and this allows the extinct creatures to be preserved in all three dimensions. Riversleigh has cast new light on pre-outback Australia and its colorful cast of animals, including tiny ancestral koalas, cow-sized wombats and fearsome land crocodiles. Altogether the site preserves roughly 20 million years of evolution that range from the end of the Oligocene to the dying days of the Miocene. This period is known as the heyday of mammalian evolution everywhere and this held true for Australia as well.

The evolution of kangaroos at the site was in overdrive here with many different genera. They ranged from being quite recognizable to being completely bizarre. One of the newest kangaroos from Riversleigh is the oddly named Cookeroo. The fossils were studied by a team comprised of Kaylene Butler and other researchers from the School of Earth Sciences at the University of Queensland in Australia.Two species of Cookeroo existed here, somewhere between 23 and 18 million years ago during a time known as the early Miocene. They were at the lower end of the scale in terms of dimensions, equaling a very small wallaby in size. Butler and team classified the new animal by using a sample of about 69 other kangaroo species.



Little Cookeroo was also unable to hop. Instead, it had to move like just about any other small mammal, by scurrying along the forest floor in search of new leaves and shoots. It was a nondescript little creature that lived alongside a plethora of far more unique creatures. Among these were the somewhat larger fanged kangaroos. Despite their name and the size of their incisors, the fanged kangaroos were herbivorous. They would have used their fangs in territorial display like other herbivores that have large, projecting teeth. These fanged kangaroos were probably also competing with the primitive Cookeroo and its relatives for food. Bigger and more advanced though the fanged roos were, they seem to have been effectively driven to extinction, possibly by the newer and more generalized roos. At the same time, Butler and team are unsure of why Cookeroo’s lineage survived while its contemporaries vanished as time went by. They hope that Riversleigh and the weird early roos will give up their secrets soon enough.
3986b46bb4f35aa1ff4d42167a12e0fc

Vasika
Udurawane

Writer


http://sulc.us/fj485
http://www.eartharchives.org/articles/the-little-kangaroo-that-couldn-t-hop/