Tuesday, 10 September 2002.

Monthly Meeting of the Essex Rock & Mineral Society

Baryonyx walkeri: the Excavation, Preparation and Replication of a Dinosaur

The talk given by Adrian was essentially about the conservation and preparation of fossil remains. Baryonyx Walkeri was used as a case study in this instance as our guest speaker has had the luxury of being in on the original excavation and all aspects of the subsequent work undertaken by the Natural History Museum.

For the initial excavation of blocks containing fossil remains Adrian advocated the use of an assortment of small chisels and a lump hammer. He said that this gave more control than using a geological hammer. The essential aspect of this work is to proceed slowly so as to ensure that no damage or at worst minimal damage occurs.

In the case of Baryonyx, there were some 55 blocks in all that required freeing. Due to this vast amount, and the importance of recovering as much information as possible, a site map was constructed showing the relationship of all the material. The lesson here is that everything we collect should be correctly recorded for future reference.

Adrian discussed the various methods of encasing large specimens in preparation for lifting and subsequent transport. The two methods used were; plaster casts and expanding foam. In both cases the specimens were first protected by a multi layer system starting with acid free tissue. He said that it was essential to provide a covering that would not react in anyway with the specimens. The tip for the collectors amongst us, was to wrap our finds in acid free tissue and place these in plastic food boxes, with either additional tissue, or bubble wrap to prevent movement. This would provide excellent protection and temporary storage until the specimen could be dealt with.

Once back in the laboratory work on recovering the fossil remains from the blocks begins with the removal of outing casing of either plaster of paris bandages or expanded foam. It is here that problems can occur. Adrian prefers dealing with the plaster encasement over the foam, as the later has too many toxic properties. Even though the laboratory is equipped with effect ventilation extraction system the removal of the expanding foam casts has been known to cause a reaction with asthma sufferers.

The next stage of recovering the fossil remains from the blocks is a painstaking and slow process. Many small tools including dental tools; like drills and burs, small air-chisels (miniature pneumatic chisels), diamond saws, and air abrasive guns (sandblasting) are used. The laboratory is equipped with piped compressed air to drive the the air tools.. In fact any tool considered of use is press ganged into use.

The principle is to remove material slowly so as not to damage the fossil remains. Any tool marks that are imparted to the fossil are catalogued so that these cannot be confused with natural artefacts during later research. Adrian admitted to making one awful mistake when preparing Baryonyx, he cut completely through a tooth! Oh dear.

Once the fossils remains have been removed from the matrix, the next stage is to reassemble all the parts. In the case of Baryonyx, the remains were disarticulated, probably as a result of scavenging. Many of the fossil bones where broken (possibly as a result of post fossilization events). The method of reconstruction was to glue the pieces together and apply filler to bridge the gaps. Simple as it may seem there are a few rules that are applied. All glue and filler must be of a suitable contrasting colour so as not to be confused with original fossil. Additionally, glues and filler must not react chemically with any of the fossil. All reconstruction work must be capable of being undone without damage to the original fossil remains. Here, Adrian discussed in depth the problems with modern adhesives. (It is worth saying that one just doesn't know what effect modern glues will cause, my advice is to have a look at the techniques used by Victorian conservators and use those that have proved themselves over time. One can always experiment on the less important finds or perhaps even contact those in the know, like Adrian, for some advice. RC) One of the new generation of glues used on Baryonyx, resulted in the appearance of a purple bloom some years later. Needless to say, this one is not used anymore.

Adrian talked about the importance of making replicas for other museums and researchers. The claw of Baryonyx has been replicated in detail and is suitable for electron scanning and silicon peels. The commissioning of a complete specimen of Baryonyx costs about £40,000.

The talk was backed up by a fine display of replica disassembled parts and reconstructed 'CLAW'. We were also privileged to have a few actual fossil remains to view. These had been allowed out for the occasion. Adrian had also brought along many of the tools he uses. I just loved the miniature pneumatic chisel, an bit like a chunky metallic Biro!

As for the 'CLAW', and it's purpose. Features like this do not just appear for no reason, they are there because they offer a distinct advantage to the survival of this species (feeding, locomotion, reproduction all that Darwinian stuff). Interestingly, Adrian said that fish scales of Lepidotes were found amongst the fossil remains and these appeared to have been etched, possibly by stomach acids during digestion. My mind started to run riot again. Is the claw for fishing, is Bary....... a specific feeder, or did the fish disagree with him (or her) so it went belly up? Claws are very interesting, just look at the differences between cats & dogs. Do keep an open mind on the subject

It was a fine talk and gave one an insight into the work and people behind the scenes. From the amateur's point of view, it should be noted that the operatives exposure to fumes, dust and vibration caused by this work are tightly controlled. Health and Safety are always paramount. We on the other hand are from the 'kitchen sink workshop school' so please consider the risks to yourselves through exposure to these hazards. The preparation of Baryonyx, like may large finds, was not a quick job. A combined total of 10 man years for this one.

I have deliberately not talked about 'Baryonyx walkeri' in any detail. The Natural History Museum and other websites say it all already (Some good, and some total rubbish, beware!). Start here!

Sorry, no pictures again this month, nobody brought along any specimens from the Walton trip or anything else. Oh dear!

© Roger Coleman 25/09/02