Australian Prehistoric Mammals

The Riversleigh Fossil Site
Before the 1983 discoveries at the world heritage listed Riversleigh fossil sites a mere 70 species of older fossil land mammals were known for the whole of the Australian continent. This was a miserably low number for a continent the size of Australia. Considering the uniqueness of Australia's kangaroo, platypus and koala, it has long been a source of frustration to the world's scientists to know so little of what must have been an equally amazing fossil record. 

Since 1983 the preserved remains of thousands of ancient inhabitants of northern Australia including giant pythons, carnivorous kangaroos and marsupial lions, have been recovered from Riversleigh. Almost half of what we know about the evolution of Australian mammals in the last 30 million years comes from bones found at a single site in the Riversleigh fossil beds. Amazingly half of these bones were unearthed in one hour. 

Although Riversleigh will not fill in all the gaps in our knowledge about the history of Australia's land animals it has doubled previous knowledge in this area and has already provided the biggest single step in this direction.

Australian Mammals
All animals classified as mammals have the following combination of features (as well as many others not listed here): hair, milk, a diaphragm, sweat glands, a constant body temperature and a dentary bone in the lower jaw which articulates the jaw with the skull. There are three groups of living mammals: the monotremes, marsupials and placentals. However, there are many other groups known from the fossil record. 

The mammals of Australia are perhaps its best known group of vertebrates. Creatures such as the platypus, the koala and red kangaroo are so well known that they have come to be internationally regarded as symbols of Australia. 

A few of the Riversleigh Mammals
The fossils found at Riversleigh represent three periods in time;
  • 25-5,000,000 years - Miocene
  • 5-2,000,000 years  - Pliocene
  • 2,000,000 - 10,000 years - Pleistocene

 

Litokoala

Litokoala
The rainforest koala, was very similar to the modern koala, living in trees and feeding on leaves. Koala fossils are relatively rare compared to other marsupial families.


Obdurodon

Obdurodon
(Obdurodon Dicksoni) The Obdurodon is not Australia’s oldest monotreme (Strepodon and Kollikon are older). It looked like the modern platypus but was larger, with a larger bill that contained teeth, unlike the modern variety. Obdurodon lived much like today’s platypus. The skull of Obdurodon is one of the most perfectly preserved fossils from Riversleigh.


Propleopus

Propleopus
Carnivorous kangaroos from the pliocene and pleistocene. The last pleistocene survivor of the lineage propleopus oscillans, stood about two metres tall.


Wakaleo

Wakaleo
(Wakaleo Vanderleuri) A medium sized marsupial lion. They stalked their prey on the ground and in trees and like the rest of the marsupial lion groups had the highly specialised teeth perfect for stabbing and cutting. Their closest living relatives are wombats and koalas. Wakaleo was one of the largest predators during the middle to late Miocene.


Palorchestes

Palorchestes
(Palorchestes Azael) About the size of a horse, this creature had huge koala-like claws, large powerful limbs, a ling ribbon-like tongue and an elephantine trunk. Its unusual appearance suggests Palorchestes lived by pulling up shrubs and eating the tubers or by stripping bark from trees to gain access to the soft inner layers.


Diprotodon

Diprotodon
This is not Diprotodon, but a Diprotodontidae Silvabestius Johnnilandi. It is one of the smallest and rarest of the diprotodontidae. The best-known fossils of this species are the “Madonna and Child”, a mother and pouch young preserved together.

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