Australia: The Land Where Time Began

A biography of the Australian continent 

Riversleigh Turtles

Turtles are found in the mostly aquatic sites such as System C's Ringtail Site and Quentin's Quarry Site, where turtle remains are common. In some sites the skulls and shell fossils from a number of different turtles associated with fish, mostly lungfish, gastropods and mammals. Complete skulls and shells have been found in some sites. Some of the shells have partial skeletons associated with them. At one particular site thousands of turtles were compacted together, making it unique in Australia, other accumulations of remains like this are unknown anywhere else in Australia. 

The gravels of the Terrace Site, dating from the Pleistocene, have produced a turtle from the megafauna of Australia, Elseya lavaracki. Few megafauna turtles have been found in Australia. The finds at Riversleigh indicate that during the Oligocene and Miocene Riversleigh had a very diverse and plentiful turtle population. Among the freshwater turtles found at Riversleigh are the groups chelids and meiolaniids.

Chelids (side-necked turtles)

The extant chelids belong to 5 genera, Chelodina, Elseya, Emydura, Pseudemydura and Rheodytes. It is believed that these turtles diversified as the Australian river systems developed. Prior to the discovery of turtles at Riversleigh the only material this hypothesis could be tested against were some Tasmanian fossils from the Middle Tertiary.

Chelid remains from Riversleigh now include 4 of the 5 genera, all except Rheodytes. Included among them is the oldest known Chelodina. They are thought to be closely related to chelids from South America. As well as the earliest fossils of Pseudemydura and Elseya. Prior to the Riversleigh finds the genus Pseudemydyra was known only from a single extant species, the swamp turtle (P. umbrina),  isolated to 2 swamps to the north of Perth. It is probably the most endangered reptile in Australia. The fossil Pseudemydura is very similar to the extant species P. umbrina

Meiolaniids (Meiolaniidae - giant horned turtles)

These are known from the Pliocene of Australia, and from the Pleistocene and Holocene of Australia, Lord Howe Island and New Caledonia. Pleistocene specimens have been found with 1.5 m-long shells and are estimated to have weighed about 500 kg. On the top of the skull they had horn-like projections and their tails had spikes or clubs. They are believed to be of Gondwanan origin, having also been found in South America and Madagascar. Based on shell fragments, they are also believed to be present in central Australian deposits from the Oligocene and Miocene.

Evidence from some Riversleigh sites indicates that these giants were quite common in the area during the Oligocene and Miocene. Many weathered limestone tors show large shells and limbs of these turtles. Parts of a primitive horned turtle have been found at Riversleigh, partial skulls, tail rings and limbs, from terrestrial and freshwater deposits dating to the Oligocene and Miocene.

Sources & Further reading

  • 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