A long time ago in the dim and distant past on here I wrote about fossil chimeras and mounting skeletons and have since written about fake fossils of various kinds. In these I rather breezed over some of the different ways that fossils can be produced for display and it seems worth going over in a little greater detail and roughly defining a few terms to make things easier for people to understand and distinguish between the various things out there.
Increasingly, genuine fossils of large animals are not on display in museums. These are expensive and valuable artefacts and scientists need to access them, and the museums need to protect them. Big dinosaur mounts that tower into the air made up of original fossils that are hundreds of millions of years old are therefore rare. They are hard to examine, and difficult to keep clean and if they ever fell over…. However, even the most complete of big dinosaur mounts are often not as they seem and can be completed using a number of different techniques.
Here then are the ways that you can complete your dinosaur fossil:
1. Original material. While these are becoming rarer, there are a significant number of mounted skeletons being produced composed mostly or entirely of original fossil material. Since there are pretty much no *totally* complete dinosaur skeletons in 3-D, the odd part of another specimen may be used to fill in the gaps, effectively creating a chimera.
2. Repaired material. Even if you do have a complete specimen, the odds are there are a few chunks missing – a humerus with the end gone, teeth lost from the jaws, or the neural spines broken from a few vertebrae. These can still be used with the missing parts repaired and completed from plaster or a similar material.
3. Casts. You can of curse simply make a direct physical copy of the bones of your specimen and mount them, or from another specimen to fill in the gaps and these are casts. Most big specimens nowadays are casts of real specimens supplemented by sculptures of missing bits.
4. Sculptures. Finally, you can simply model the missing pieces from scratch and make them to fit the gaps and what you know of the existing anatomy or from close relatives. Sculptured bones run the full length from inept plasticine-like creations that look only vaguely like bones right through to superb ones that can even look better (since they have no breaks or distortions) than the originals.
Telling these different ‘bones’ apart is not normally too difficult with a little practice (though across a darkened dinosaur hall it’s not always easy). Typically original material looks organic in a way that even casts do not – natural swells and breaks and just the texture of the bones will look ‘right’. Repairs to original material are often crude, but in any case the instant change in texture and colour between a sculpted piece of plaster and the bone itself should be clear. Sculptures (whether as repairs or as whole replacement bones) often have little texture on their surface beyond a few scratches or dimples and are often a give away as their surface is so smooth. Finally casts often loose a little of the detailed surface texture of the originals from which they are copied but can usually be distinguished by their colours. Real bones generally have a range of colours (if minor) to them when casts are typically made using coloured resin or are pained after production and so are a uniform colour.
That’s quite probably more than enough of casts and sculptures, but this should serve as a guide to what is, and is not, real in museums and how to tell them apart and why this can be important.
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