Prehistoric Prototyping

Posted on: 10th October, 2007. Filed Under: News

The discovery of a hole in a block of red sandstone in a quarry near Elgin has lead to what local palaeontologists have heralded as the most exciting fossil discovery of the century. With the help of modern medical scanning techniques, the results have been more precise and productive than with any methods previously used. And much like the plot of Jurassic Park 3, experts have turned to Rapid Prototyping to advance their research and bring their discoveries to life!

The block was discovered in North East Scotland in 1997 when quarrymen (Moray Stone Cutters) noticed a hole in the rock while digging stone. Realising that it may be of importance, they set the rock aside and contacted a local Open University student, Carol Hopkins. Upon examining the sandstone block, Carol confirmed that the hole represented the mould of fossil bone.

Mouldic fossils form when an animal dies and decomposes. In desert environments, bones tend to bleach white (oxidising of the organic content) leaving only the mineral content of the bones. In the case of the Clashach Quarry mould it appears that after the bones had oxidised in the Permian desert, acid waters flowing through the sandstone dissolved the rest of the bone to leave a void.

Actually seeing the impression of these skeletons encased in rock has always been difficult. Traditionally the moulds of fossil animals were cast in rubber by filling the holes and splitting the rock, thus damaging the mould, and not always producing a satisfactory impression.

To avoid damage to the mould, Dr. Neil Clark from the Hunterian Museum in Glasgow decided to employ non-invasive techniques using modern medical scanners as well as the very latest model making methods. Initial results, as featured on Tomorrows World, were encouraging.

“CT-scanning was performed in the first instance. From the first scan it was obvious that we were dealing with the entire skull of a mammal-like reptile (dicynodont). Rendering the CT-scans produced a 3-D image of the skull which allowed us to compare it with similar fossils from around the world.”

However, not satisfied with these results, Dr. Clark decided to use a more accurate medical technique to see inside a mouldic fossil for the first time ever. Magnetic Resonance Imaging, normally used by radioligists to see soft tissue and detect tumours in humans was used in this same way to accurately detect the space in the mouldic fossil.

MRI-scanning could provide a better resolution than CT-scanning because of the finer scan thickness. To be detected, the cavity had to be filled with water prior to scanning as MRI requires a fluid to react with the magnetic field. The entire skull was then successfully scanned using MRI. The result was a fully accurate 3D image of a 250 million year old dicynodont (two toothed dog)

Laser Prototypes Europe Ltd. were then approached by Neil, enquiring about the potential of creating a solid model of the skull using Stereolithography.

LPE has several years of experience in working with MRI scanned data from local hospitals, but like others, had only ever experienced working with human skulls.

“We have worked extensively with local hospitals on creating SLA patterns to produce titanium plates for insertion or for visual aids for surgeons to help establish corrective surgery methods. It is the first time we’ve been asked to produce a 250 million year old fossil skull,” commented Campbell Evans, LPE’s Technical Sales Manager.

The Belfast based Rapid Prototyping company converted the MRI scan data to STL format to allow for the creation of an SLA model. Working closely with John Winder of the MRI department at the local Royal Victoria Hospital, they carefully set the noise level on the MRI scan to allow for a fully detailed conversion to RP format.

The data was sliced into 0.1mm thick layers and built with LPE’s Stereolithography equipment using a tough epoxy resin. Within a matter of a couple of days, Dr. Clark received a fully detailed SLA model replicating the exact features of a 250 million year old skull which had hitherto only existed as a cavity in a sandstone rock!

“The amount of detail here is absolutely phenomenal!” Dr. Clark enthused. “The use of medical scanners and Stereolithography has saved a very important fossil from being damaged by traditional methods of palaeontological investigations. The resolution obtained is enough to identify the species of dicynodont represented by the mouldic skull. In some parts of the skull, fine structures that would have been lost using rubber casting techniques, were observed and reproduced faithfully in an exact prototype replica of the data”

So, perhaps Spielberg wasn’t too far off the mark in his latest Jurassic Park instalment…

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