Scientists have created an "atlas of vertebrate decay," which documents — with pictures! — the changes a handful of species go through as they decompose. And yes, there is an actual scientific purpose behind this gruesome pursuit.
Fossils have long provided a wealth of information about how life evolved on our planet, but they're often difficult to interpret. A major issue is that animal remains don't fossilize under perfect conditions — sometimes bones are disturbed or even broken by other animals. And at other times, rot breaks down distinctive soft tissues.
One of the ways that paleontologists try to understand the fossils they're looking at is by comparing the remains with living creatures and trying to identify similar features. But this approach comes with inherent problems, too: Fossils often preserve decomposed remains, rather than pristine bodies. So if scientists really want to get a clear picture of things, they need to compare fossils with decaying bodies.
Enter the atlas of vertebrate decay, created by paleobiologist Mark Purnell, along with his colleagues Sarah Gabbott and Robert Sansom. The researchers created their decomposition guide by first rounding up specimens of six species believed to be similar to early vertebrates: the fishlike chordate Amphioxus (Branchiostoma lanceolatum), the Atlantic hagfish (Myxine glutinosa), two lampreys (Lampetra planeri and Lampetra fluviatilis), the spiny dogfish (Squalus acanthias) and the lesser-spotted catshark (Scyliorhinus canicula). They then periodically photographed their (dead) specimens as the creatures rotted in water for up to 300 days.
Sometimes, [the images] show that "what may be the most useful [body] parts for identifying a fossil rot away first," Gabbott says. Soft cartilage and distinctive muscle tissues, for instance, can melt away within weeks. But the atlas also highlights hardier structures that could help scientists separate special fossils from the ordinary. A decayed shark, for instance, looks suspiciously like an "enigmatic," 400-million-year-old fish fossil found in Scotland that some researchers believe could be an early vertebrate ancestor, Purnell says.
The researchers describe the animals' decay patterns — from their eyes to their hearts to their fins — in a paper in the journal Palaeontology, which is currently accessible to all. And it includes copious photographs. Though they only looked at a small group of vertebrates, the team suggests that their methods and techniques can be applied to other clades of soft-bodied organisms, too.
Top image: Progressive stages of decay of the the lancelet amphioxus. Courtesy of Mark Purnell, Rob Sansom, Sarah Gabbott, University of Leicester.