The Gruesome ‘Atlas of Vertebrate Decay’ Does Have a Practical Purpose

Some of the earliest ancient vertebrates were too squishy to leave easily identifiable remains that lasted through millennia, so researchers are creating a rot look-book

Mmm, rotting vertebrates. Lampreys, catshark embryos and hagfish in three states of decay, progressing from left to right. Photo: Sansom et al., Paleontology

The Atlas of Vertebrate Decay is gruesome, yet useful. Gruesome, because its authors aimed to create a visual composite of sharks, lampreys, hagfish, and other spined creatures in various states of decay. Useful, because their goal was to help scientists better identify puzzling fossil remains. In their studypublished in Paleontology, the authors explain the problem:

The origin of vertebrates represents a landmark event in the history of life on earth.

Despite its great potential, however, the fossil record of these events is hard to read, and interpretations remain equivocal. Of the several fossil taxa that have been discussed in the context of vertebrate origins and early evolution, many have proved to be highly contentious in terms of interpretation of their anatomy.

All too often, direct comparisons are made between the morphology of fossils and the pristine anatomy of living relatives. Pristine anatomy is not, however, a suitable comparison.

In other words, some of the earliest ancient vertebrates were too squishy to leave easily identifiable remains that lasted through millennia. The fix? Create a database of ancient vertebrates’ nearest living relatives in all states of rot. ScienceNOW explains the unappetizing process: 

First, they collected living specimens of six species that researchers believe are similar to early vertebrates, including the Atlantic hagfish (Myxine glutinosa), jawless lampreys, a couple of sharks, and the fishlike chordate known as Amphioxus.

Once back at the lab, the team let specimens rot in water for as long as 300 days, periodically photographing the disintegration.

From those pursuits, they produced dozens of photos. Some surprises emerged from the decay. Sharks, for example, resemble a certain 400-millon-year-old Scottish fish fossil that may or may not be an early vertebrate ancestor, ScienceNOW says, while the team discovered that some of the most potentially useful body parts, like tell-tale cartilage and distinctive muscle tissue, tends to be some of the first matter to go when the decomposition kicks in. Their images show just what may last the squeeze of time and geology, and what does not. They conclude:  

Complex and repeated patterns of transformation during decay are identified and figured for informative character complexes including eyes, feeding apparatus, skull and brain, muscles, branchial apparatus, axial structures, viscera, heart and fins.

The methods and techniques outlined are eminently applicable to other clades soft-bodied organisms and demonstrate a new way to interpret the exceptionally preserved fossil record.

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