Australia: The Land Where Time Began

A biography of the Australian continent 

Toolebuc Limestone

The marine Toolebuc Formation, of Aptian age, is situated on Warra station near Boulia, western Queensland.

This deposit is exposed near Boulia, along the Hamilton River, in southwestern Queensland. At this site a small number of bones have been found, apparently from the same species of pterosaur, vertebrae, parts of both limb girdles. The remains are sufficiently characteristic to allow it to tentatively assign the bones to the genus Ornithocheirus, a genus found also in Brazil and Europe. It is one of a few pterosaurs known from Australia, and the bones are not crushed. Pterasaur bones are similar to those of birds, in that they are hollow and thin, making them fragile, so it is not common to find them is such good, uncrushed, condition as these are, allowing the shape and articular ends to be seen. These fossils are in limestone that was never far below the surface and their 3-d structure has been preserved. In spite of the paucity of the available material, these fossils show features of pterosaur bone that can only be guessed at in fossils from elsewhere in the world where they are usually crushed flat.

There are also 2 specimens of a very primitive bird group, the enantiornithines. A single fragment of hind limb (tibiotarsus) from a bird (Nanantius eos), about the size of the Australian shrike-thrush, was found in the Toolebuc Formation. Another tibiotarsus from this group has been found, similar to material from this bird subclass from Mexico and Mongolia, but the most abundant remains are known from the Cretaceous of Argentina. 

The Australian enantiornithines material is the only known bird of this subclass in the world. Outside Australia is is known only from the Late Cretaceous. The early form of bird didn't evolve many of the specialisations acquired by modem birds, such as the shape of the articular surfaces of leg bones and the pelvic structure. The wing bones are very similar to those of modern birds. Birds that gave rise to modern avifaunas had replaced them by the end of the Mesozoic.

Sources & Further reading

  1. Patricia Vickers-Rich, Thomas Hewitt Rich, Wildlife of Gondwana, Reed Australia, 1993
  2. Long, John A, 1998, Dinosaurs of Australia and New Zealand, University of New South Wales Press.
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                                                                                           Author: M.H.Monroe  Email: admin@austhrutime.com     Sources & Further reading