NOVA Online | The Missing Link | Confessions of a Preparator

One hand on a specimen of Ichthyostega, a tetrapod that lived during the Devonian Period, Sarah Finney takes a break from her work at the University of Cambridge.

Confessions of a Preparator
by Sarah Finney

My progress toward becoming a preparator began, I think, quite early in my life. While growing up along the Welsh border with England, I used to collect fossils from deposits of the Silurian and Devonian periods (438 to 360 million years ago). This pursuit gave me an intrinsic feel for and love of fossils. Later I studied archeology and also worked in this field for a number of years.

It was during my stint in archeology that I learned the preparator's most vital tool: patience. (Or is it just stubbornness?) This is particularly pertinent when working on the material from the Devonian of East Greenland, which forms the foundation of our research. That's because most of the specimens are in fairly intractable matrix, the rock in which fossils are embedded.

My job is a matter of wearing the matrix away grain by grain using dental drills and a lot of one-millimeter-diameter tungsten carbide rod. I cut this rod to length, mount it in a pin vice, and sharpen it to a fine point on a bench grinder with a 120-grit wheel. Because of the brittle nature of tungsten carbide and the hardness of the matrix, I am forever breaking the tip off my needle. If a genie were to appear before me one day, I would not wish for a new car or a swimming pool in my back garden but for an ever-sharp point that never breaks.

I carry out all my work under a binocular microscope, because most of our specimens are quite small, and we are interested in detailed points of anatomy. In fact, this meticulous preparation is a speciality of our lab. Using a microscope also enables me to see the fine color or textural distinction between bone surface and matrix.

One grain at a time: Fossil preparation requires concentration, a steady hand, and a depthless well of patience.

One characteristic of the early tetrapods that we study is that the dermal bones of the skull have a sculpted or ornamented surface texture. (Imagine an overturned egg carton in miniature.) This surface is particularly difficult to prepare and slows up the whole process. (Imagine encasing that egg carton in concrete and then having to excavate it.) I enjoy the challenge, however, and there is also the added interest of chasing sutures, the lines where the various bones of the skull meet, and sensory pits, the slight depressions in the skull that contain sensory cells.

There are no tools that are specifically made for mechanical preparation, so we tend to rely on "found" devices such as dental drills. I have several dental catalogues showing gruesome pictures of rotten teeth, and when we need new drills, I flick through these sections (quickly). For removal of large amounts of matrix, I use a pneumatic pen. This is really designed as an engraving tool, but it does the job very efficiently.

It is also possible to do a lot of damage with the pen. While removing large amounts of matrix, it is easy to become bored and stop concentrating. I might have my headphones on and be listening to music on the radio, for instance, and it is always in that split second of listening more than looking that I contact bone and don't notice. Oh dear, time for a tea break. Luckily, this doesn't happen very often.

A glance at Finney's toolkit: In the center of the image rests a sandbag that supports a fossil specimen. Hovering over the specimen is a binocular microscope with a Plexiglas screen to minimize dust intake by the operator. To the left of the sandbag are a black-tubed fiber-optic light source and a flexible blue air line for blowing away rock dust and chips. In the lower left of the image are two paintbrushes for applying consolidant, while in front of the sandbag lie a mounted needle with a tungsten carbide rod point and a reciprocating dental handpiece that also holds tungsten carbide rod. On the tray at right stand bottles of consolidant and solvent.

I also care for any specimens in the museum's collections that have suffered from overzealous consolidation in the past, usually with some evil Victorian concoction made of boiled horse or other unpleasant ingredients, coupled with decades of dust and soot. (Consolidation differs from gluing in that it's meant to stabilize specimens that might have, say, flaky or crumbly surfaces.) I will clean and stabilize the specimen and try to return it to its former glory. On our specimens, we use methacrylate resin for consolidation and gluing, but only when necessary. I believe the best policy with preparation is knowing when to stop, though quite when I cease being a preparator and become a conservator I can't say.

On a good day I will arrive at the lab knowing I have an interesting problem to solve. Sometimes I become so engrossed in my work that it almost becomes meditative. There are those days, however, when an infinite number of vertebrae stretches ahead of me. I know I have to do the work, but it can be difficult to apply myself. That's when the stubbornness comes into play. In the end, despite the seemingly endless piles of rock, I will not be beaten.

Several years ago I spent considerable time working on a striking skull of Acanthostega, the Devonian creature whose discovery has changed our understanding of the fish-to-land-animal transition (see Diva of the Devonian). We called the specimen Grace, because at one stage of preparation it looked a bit like the pop superstar Grace Jones. The skull has a very distinctive grin, which grew more and more apparent over the months I worked on the specimen. Eventually I began to think that Grace truly was grinning at me. This is when you know it's time to go on holiday and get lots of fresh air.

When your specimen starts smirking at you, Finney says, "you know it's time to go on holiday and get lots of fresh air."

As I mentioned, I listen to the radio while I work, and after a while I begin to associate certain specimens with something I've been listening to. The lateral line pits on Grace will always remind me of a radio dramatization of Chaucer's Canterbury Tales, while the vertebral columns of a pair of Acanthostega specimens we named Spot and Patch trigger thoughts in my mind of the Christmas ghost story season on BBC Radio 4.

The real satisfaction of preparation comes not just from having a really obscure job that no one has ever heard of—great for cocktail party conversation—but from turning a really unpromising piece of rock into a beautiful object that once again looks as if it were a living animal and that may end up filling in some gaps in vertebrate evolution. You definitely give a bit of yourself in the process: The toll is both physical (your wrists and elbows can suffer) and mental (because of your intense relationship with a specimen over several years, it somehow becomes a part of you). But it's worth it.

Sarah Finney has worked since 1989 as a fossil preparator at the University Museum of Zoology Cambridge in Cambridge, England. Funded by the Natural Environment Research Council, she works with paleontologist Jenny Clack on the fish-tetrapod transition, a key moment in vertebrate evolution. In 1998, Finney joined Clack and two others on a women-only expedition to East Greenland to collect more Devonian tetrapod fossils, enough to keep her busy, funders willing, for years to come.

Photo credits

Printer-Friendly Format

Feedback