As I wrap up revisions on a manuscript, as well as continuing the day to day work in “my” museum collection, I’ve been thinking a lot about what makes a good figure of a fossil. The thought is driven in part by wanting to illustrate the specimens we’re describing in detail, but it’s also driven by the need for my co-workers and me to be able to identify specimens as they come in from the field.
Illustrations, ideally, are used by more than just the few specialists on a group. Life at a museum makes me realize just how much collections staff* need good illustrations, too! It also makes me experience the complete inadequacy of the figures in the great majority of papers. Much of this inadequacy, I suspect, stems from historical space limitations in print journals…now that that is changing (for at least some journals), it’s a good time to talk about what makes a well-illustrated fossil.
*edit: and amateur collectors! I realized I had left this out in my initial post.
Lots of views
Most fossils are highly three-dimensional objects, so multiple views are essential to capture the anatomy. Unless we’re dealing with a heavily flattened fish or leaf imprint, multiple views are essential. An oblique view is nice too–sometimes that’s what it takes to better highlight a particular feature. Even better? 3D models. In ascending order of usefulness, this includes movies, 3D PDFs, and printable, freestanding 3D files (e.g., STL or PLY format).
Every fossil needs some interpretation, particularly in the case of skulls and other complex fossils. A good drawing will indicate sutures, important holes, and other features that may not be easily visible on a photograph. [Note: this includes not just line drawings, but also other renderings–a skilled artist can work wonders with a fossil!]
This should be a no-brainer, but it is amazing how many journals require high-resolution figures at submission and then publish heavily down-sampled images. This is a waste of the authors’ time, and it reduces the utility of the image for the reader. That extra bit of zoom can be really valuable sometimes, particularly for multi-part figures!
It is incredible what things pop out in a color versus a grayscale image. Areas of reconstruction, crushing, and changing bone type are often far more easily seen when all of the color data are left intact. Thankfully, many journals now encourage color images, even if the printed copy remains in grayscale.
Grayscale / Color-Free
Yes, this goes against everything I just said above. Some specimens, depending upon preservation, are mottled to a point where it is difficult to pick out morphology. In this case, a color-free representation can be invaluable. This is best achieved by either coating specimens with an appropriate substance (as in the above image), or digital scans reconstructed without the obstructing colors.
Fossils rarely manifest as complete skulls or highly diagnostic elements. Sure, teeth are the most diagnostic part for many mammals, but what about the rest of the skeleton? Many collection drawers are filled with isolated and unidentified wrist and ankle bones, the durable blocky elements that fossilize so nicely. Unfortunately, they’re often very poorly illustrated in the literature! Good luck trying to “figure out” an entocuneiform or a navicular (pun only somewhat intended). Collections staff and researchers can spend a lot of time trying to identify common, complete, and clearly diagnostic elements that just don’t have comparable material widely figured in the literature (particularly in the absence of a good, identified comparative collection). This even applies to some quite common fossils. For instance, horse teeth are quite well illustrated, but it’s surprisingly difficult to find figures of individual vertebrae or some of the more obscure ankle bones.
As scientists, we should strive to make our work as accessible, reproducible, and useful as possible. Comprehensive and clearly rendered figures are essential for achieving this goal.