Australia: The Land Where Time Began

A biography of the Australian continent 

Riversleigh Phalangerids

Brushtail possums are found in almost all habitats in Australia. They were even common in the gum trees that fringed waterways in central Australia until recently. One of the most often seen marsupials is the common brushtail possum, Trichosurus vulpecula. Related possums are the scaly-tailed possum (Wyulda squamicaudata) and many species of cuscus of the genera Palangaer, Strigocuscus, Spilocuscus, Ailurops and Phalanger. All the phalangerids are about cat-sized or larger and omnivorous to some to degree. The omnivory of the common brushtail possum is given as a main reason for their ability to survive and even flourish in a time of high levels of habitat destruction.

One of the oldest known possums of this type, known from a small fragment of a jaw, was found in the Miocene deposit at Geilston Bay Local Fauna. Trichosurus hamiltonensis and Strigocuscus notialis have been found in the Hamilton Local Fauna from the Early Pliocene.

At least some phalangerids have been found at Riversleigh, Trichosurus dicksoni, Strigosurus reidi and Wyulda sp. are examples. These genera all contain living species, and are also found in the Riversleigh rainforest from the Early to Middle Miocene.

The most common of the Riversleigh phalangerids is the brushtail possum, T. dicksoni. In some features it is more primitive than living species, it is as common in the Riversleigh rainforests as are T. caninus, the only rainforest species, is at the present. This also applies to the brushtail possum Trichosurus from the Hamilton Local Fauna in Victoria. This genera is intermediate between those from Riversleigh, that appear more primitive, and the more derived modern species. Based on this there appears to be little difference in diversity or abundance between the modern species and the most primitive species over the past 20 million years. The same also applies to the Wyulda lineage. Only 1, relatively rare species, is extant. There was also 1 rare species living in the Oligocene-Miocene. With this lineage there has also been no noticeable change in the diversity or abundance over time.

Strigocuscus reidi appears to have been the only cuscus species present in the Riversleigh rainforests during the Oligocene-Miocene. The same rarity seems to have applied to the same single species of cuscus known from the Hamilton Local Fauna. In small rainforests patches of north-eastern Queensland there are presently at least 2 species, and in the rainforests of New Guinea and the nearby islands there are at least 13 species. It has been suggested that the rainforests of  New Guinea and the adjacent islands may have been a centre of diversification after the end of the Oligocene.

Riversleigh and Hamilton are the only places where Trichosurus species and Strigocuscus species are sympatric.

Sources & Further reading

  1. Michael Archer, Suzanne J. Hand & Henk Godthelp, Australia's Lost World: Riversleigh, world heritage Site, Reed New Holland
Author: M. H. Monroe
Email:  admin@austhrutime.com
Last Updated 25/02/2011

 

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                                                                                           Author: M.H.Monroe  Email: admin@austhrutime.com     Sources & Further reading