An article published in the journal “Nature Communications” describes the extraordinary study on the eyes of fossilized specimens of Dollocaris ingens, a crustacean that lived about 160 million years ago, in the middle Jurassic. In the deposits of La Voulte, in the southeast of France, fossils were found in which various soft tissues were also well preserved and this allowed to reconstruct their eyes, giving us an idea of ​​how they saw and indirectly of the environment in which they lived.

Paleontologist Jean Vannier, zoologist Brigitte Schoenemann and other scientists in Cologne and Lyon took advantage of the high quality of Dollocaris ingens fossils to prove that at the time there were creatures with very sophisticated eyes. Using the techniques of X-ray microtomography, they reconstructed the three-dimensional structure of these ancient crustaceans.

These exams allowed to discover that Dollocaris ingens had eyes formed by 18,000 ommatidia, a record that to our knowledge was only surpassed by dragonflies, whose eyes have by far the largest number of elements with 50,000 ommatidia. Each of these elements contributes to form the image seen by the animal because each of them contains a structure composed of cornea, lens and retina.

The vision is given not only by the number of ommatidia but also by their density and by the overall size of the compound eye. In the case of Dollocaris ingens, density was more than 500 ommatidia per square millimeter and its eyes made up about a quarter of the length of its body.

The researchers’ conclusions based on these data are that the Dollocaris ingens was a predator that lived in well-lit environments, where it could use its sophisticated eyes to find his prey. Previously, paleontologists thought that at that time in that area there were deep water and therefore quite dark.

This research on Dollocaris ingens is unique also because this species was assigned to the class of Thylacocephala, arthropods that developed in the Silurian and perhaps even earlier and became extinct in the late Cretaceous. Their relation with other crustaceans is still under discussion so the studies based on similarities to other species were approximate. Now the hypotheses on them can be based on direct examis of the specimens found in La Voulte.

The analysis of fossilized soft tissues and the subsequent reconstruction of their structure was considered impossible until not long ago. Today, however, the increasing application of advanced technologies typically used in the medical field is leading to extraordinary achievements in the field of paleontology as well.