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The virtual and physical preparation of the Collard Plesiosaur
 
SPPC/GCG Conference
 
Platform presentation (20 minutes)
Authors
 
*Nigel R Larkin
 
Abstract
 
The ‘Collard Plesiosaur’, found in 2003 in Bridgwater Bay on the Somerset coast, has been described as ‘probably the best preserved and most scientifically valuable fossil plesiosaur to have been found in the UK for at least 150 years, possibly ever’ (Richard Forrest, SPPC/SVPCA 2005). The skeleton is almost complete and variably-mineralised.

The skeleton (possibly a juvenile Rhomaleosaur) was preserved in Lower Liassic Kilve Shales - a fine-grained, thinly laminated rock containing little or no cement. Held together by compression, this lithology is notoriously susceptible to fluctuations in humidity, severely compromising the integrity of specimens once dry.

The priorities for the project were to arrest shale delamination caused by environmental fluctuations and to prepare the specimen for research. The specimen appeared to be well fossilised in a homogeneous, un-cemented matrix, offering excellent potential for X-radiography. Therefore before preparation commenced the specimen was X-rayed and CT-scanned with stunning results, despite some of the limb bones not being well mineralised. This virtual preparation helped to inform the subsequent physical preparation of the material.

Investigations were undertaken to select the most suitable tools, materials and techniques to conserve and prepare the specimen. Attempts to consolidate matrix samples with the methacrylate co-polymer Paraloid B72 were generally unsuccessful – the shale layers distorted and delaminated. However, B72 was successfully applied to the sides of the specimen blocks providing a humidity seal.

Mechanical preparation commenced with the removal of underburden, greatly reducing the specimen’s weight. The use of a scalpel proved to be the most appropriate technique for developing its surface and exposing the skeleton, removing one paper-thin layer of shale at a time.

London 2020