The prehistoric sea creature Dunkleosteus terrelli had the strongest jaws ever for a fish, according to a recent study. Artists' renderings of the animal show an iron-jawed leviathan, sometimes with a nasty underbite. How do you draw an extinct animal?
Start with the skeleton. The only definite indicator of an ancient animal's size and shape comes from the fossil record. In the case of Dunkleosteus, which went extinct 360 million years ago, the only fossilized remains are its head, jaw, and the armor that extends part of the way down its back. The rest of the fish's body was cartilaginous like a shark's, and therefore didn't preserve. By looking at the skeletal remnants with an expert, an artist can usually determine how the bones articulate, or fit together, and what movement that configuration allows for. Knowledge about the animal's structure and mobility helps the artist choose its position and activity in the picture.
Where the skeleton ends, speculation begins. Sometimes it helps to refer to modern descendants. Some artists give the Dunkleosteus a sharklike dorsal fin, for example, even though no one knows for sure whether it had fins at all. Dinosaur artists who use vivid palettes often cite colorful birds and iguanas to support their choices. Ancient relatives are a good guide, too. We know that Dunkleosteus was in a class of armored fish called the placoderms. Other members of the class were more fully preserved, and the proportions of their fossils suggest that the Dunkleosteus was about 25 to 33 feet long. More superficial features—like the texture and color of the skin—are subject to artistic license.
Paleontologists use illustrations of extinct animals for scientific publications, museum exhibits, and popular books. Most natural history museums have in-house artists available for this work, but if they need something very specific—a particular artistic style, say, or a specialized animal—they may hire an outside firm. In general, the work proceeds in an extended, and sometimes excruciating, back-and-forth, in which the artist sketches ideas and the scientists recommend tweaks. This process can take anywhere from a few days to several months, depending on the speed of the artist and whether the research team is describing an animal that's never been drawn before.
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The Explainer thanks Gretchen Baker and Mark Westneat of the Field Museum in Chicago and Philip Anderson of the University of Chicago.