NOW THE HARD WORK BEGINS ...

Now that the dust, or in our case sand, has settled after the 2016 field season at the Eric the Red West site on the Otway Coast, south-west of Melbourne, the hard work of removing the fossils bones from their rocky tombs has commenced. The bones and teeth of the animals that lived and died in the area that is now part of the Early Cretaceous Otway Group, were swept into fast flowing streams and rivers, to be buried in the soft sandy sediment of the river bed. Over time the soft sediment was compacted and buried to form a hard crystalline volcano-clastic sandstone conglomerate, which now outcrops along the Otway coastline from Dinosaur Cove to Lorne on the Great Ocean Road.

The sandstone conglomerate at the Eric the Red West site does not contain as many mud clasts as the Flat Rocks site on the older Bass Coast and is therefore harder to break. This also makes it harder to prepare. The sediments do not contain carbonate cement and so cannot be chemically dissolved using acetic acid. Preparation of the sandstone conglomerate involves mechanical preparation using pneumatic air tools such as the ARO air scribe. This tool is powered by compressed air which forces the tungsten carbide tip to move backwards and forwards extremely quickly, acting like a mini jackhammer.

Most of the fossil bones from the Eric the Red West site are less than 15cms in length, which means that they do not need to be plaster-jacketed for transport. The fossil bones are discovered as the fossil layer in which they are preserved is broken down. Unfortunately, this method also results in the bones being broken as they are exposed. So it is essential that all fragments of the bones are collected and labelled before they are carefully wrapped in tissue paper and newspaper and transported to Museum Victoria.

Once the boxes of fossils arrive at the Palaeontological laboratory in the Museum, Collections Manager David Pickering and his team of volunteer preparators begin the slow process of unwrapping the fossils, ensuring that the written information that accompanies each specimen is recorded. Before preparation can commence the fossil has to be assessed, consolidated and if necessary, adjacent sections of rock and bone are glued back together again. Each fossil is unique and no fossil is prepared in exactly the same way. It depends on how the fossil bone is exposed in the rock and how well it is preserved. Some bones are solid and break cleanly, others are fragile and break into many pieces. It is important to estimate the size and shape of the bone in the rock. A limb bone which has broken through the shaft revealing just a circular or oval cross-section gives little indication as to the length of the bone or the angle at which it is lying in the rock. Some preliminary preparation maybe necessary to ascertain the direction in which the limb is lying and the length of the shaft. Once the preparator has ascertained the size and direction of the fossil then it is possible to trim excess rock from around the specimen, which can considerably reduce the overall time involved in the preparation.

Over the next few months we will follow the preparation of some of the bones that were found during the 2016 Eric the Red West field trip. I will include images of what the bones looked like when they were first discovered and the step by step process each specimen undertakes during its preparation. Hopefully it will give you some idea of the painstaking work that goes on AFTER the dig has ended.

The first specimen we will be preparing this month is a small dinosaur limb, which is broken obliquely along the shaft. At least one end of the limb is preserved, but the other end of shaft disappears into the matrix. The exposed length of the limb measures 7cms, so it is possible that the overall length of the limb could be around 10cms if the other end has been preserved. The bone is hollow and relatively thick-walled suggesting that it probably belonged to a small ornithopod dinosaur similar to Leaellynasaura amicagraphica or Atlascopcosaurus loadsi. Both these small bipedal herbivorous dinosaurs have been found at nearby Dinosaur Cove so it is very likely that the limb belongs to one of these taxa.

Preparation of this dinosaur limb will take place over the next few weeks and images of each step will be posted once it is finished. So stay tuned...

One end of limb.
Photo by Lesley Kool.

Two halves of limb.
Photo by Lesley Kool.