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Draw carefully

Modern palaeontology increasingly benefits from new and exciting methods. Techniques such as computed tomography have revolutionized our field, providing high-quality, often three-dimensional, images of the fossils in question. Yet I believe there is still a role for old-fashioned drawings; although these days a graphics tablet and associated software offer more comfortable ways of making illustrations than painstakingly inking an image onto tracing paper, shading it dot for tiny dot, and scraping away every minuscule mistake with a scalpel!

But why take the trouble to illustrate fossils at all? Isn’t a decent photograph sufficient? It’s an old, but true, adage that a picture paints a thousand words, but a good scientific illustration isn’t just a pretty picture — it is also part of a hypothesis. Not all fossils are perfectly preserved, and from the mass (or sometimes mess) of lines, scratches, or imperfections in the rock matrix, palaeontologists have to tease out what is biologically relevant — what really belonged to the original organism — and what is unimportant or distracting. These distinctions are often crucial to how the fossil is being interpreted, and are not obvious in a raw photograph.

Taking time to draw a fossil carefully under the microscope helps me better understand the specimen by forcing me to make decisions about what I can really see. Is this a leg I see before me? In the 19th century palaeontologists sometimes employed professional artists who may have spent more time looking at the material than did the scientists themselves. There are animals described as blind, even though the artist clearly put eyes on the accompanying illustration. In my own field of arthropod palaeontology it is important to accurately determine features like the number and boundaries of the body segments, the joints between the limbs or the mouthpart elements, and whether other details (eyes, spines, tubercles, and so on) are really present.

Harvestman (Opiliones) called  Caddo dentipalpus  found in the circa 25-million-year-old Bitterfeld amber of Germany.

Harvestman (Opiliones) called Caddo dentipalpus found in the circa 25-million-year-old Bitterfeld amber of Germany.

Done well, drawings offer valuable data for subsequent study, possibly years or even decades later. A good drawing outlives its illustrator, and will go beyond the original function of describing how a new species looked. High-quality figures can be used by later workers to recognize characteristics relevant for subjects such as functional morphology, or for determining evolutionary relationships. It is disappointing to receive a new publication about a potentially exciting fossil in which drawings are sketchy, or even absent, as this makes it harder to tell whether the authors have interpreted things correctly. If they claim an arthropod had 10 segments, but I suspect it should have had 11, then a drawing where they offer evidence for their count (and which can be compared directly to a photograph) would be extremely helpful.

Of course different researchers may interpret the same fossil in different ways, and this should be reflected in the relevant illustrations. For example, there is an early arthropod specimen Fuxianhuia in which some workers see extra limbs tucked under the body and others see the same structures as part of the internal digestive system. A drawing alone will not resolve this debate, but it touches on another decision the palaeontologist has to make. How much effort goes into the interpretative drawing? Should I draw the specimen to the best of my ability exactly as it appears in the rock? This is the more time-consuming alternative — which I personally favour — and assumes that all the anatomical features that are really there will emerge through the high-quality illustration. Others take a more schematic approach, and restrict the drawing to only those outline features which they consider relevant and necessary. This is quicker, and admittedly yields a neater picture, but risks overlooking finer details.

One cannot live on geophysics alone

Last day on the North Slope