The humble trilobites, helmet-headed creatures that swam in the sea hundreds of millions of years ago, hide an unusual secret – “hyper eyes” unprecedented in the animal kingdom.
By touching more X-ray From the images, researchers have found that a certain type of trilobite — an extinct arthropod closely related to the horseshoe crab — had “hyper-textured eyes”, complete with hundreds of lenses, their own signal processing and transmitting neural network and many optic nerves, according to new research. published September 30 in the journal. Scientific Report.
Related: Why did the trilobites go extinct?
Today’s arthropods, such as dragonflies and mantis shrimp, are also notable for their powerful compound eyes, which consist of many facets called ommatidia, each equipped with its own lens, like a disco ball.
But, according to new findings, the family trilobite Vacops had compound eyes that were much larger and more complex than their modern arthropod relatives. Each eye (one on the left and one on the right) holds hundreds of lenses. This primary lens, about a millimeter in diameter, is thousands of times larger than ordinary arthropods. Six (or more) are placed below it like the LEDs in the headlights of a car modeled on a typical compound eye. “So each Phacopid big eye is a very complex eye with up to 200 compound eyes each,” lead study author Brigitte Scheunemann, a paleontologist at the University of Cologne in Germany, told Live Science in an email.
Trilobites are living beings from the beginning Time Cambrium (521 million years ago) to the end of the Permian period (252 million years ago) on the ocean floor. Some may be predators that hunt water worms, although most are scavengers or plankton eaters. The remains are commonly found in limestone from the Cambrian period. But despite their presence in the fossil record, scientists still have questions about their physiology and evolutionary history.
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To answer some of these questions, the researchers used image enhancement techniques to examine dozens of archival photos, tagging them with the latest findings. In the process, they also settled a long-standing scientific debate: They confirmed that the mysterious string of “fibers” seen in X-ray images more than 40 years ago was actually a collection of optic nerves connected to the eyes of trilobites.
“It’s always difficult to infer the function of ancient, extinct organisms,” said Nigel Hughes, a trilobite expert at the University of California Riverside, who was not involved in the study. In fact, Hughes notes that even some of the strange spherical features in living things cannot be explained—for example, there is still some debate about the function of long horn-like teeth, according to Smithsonian Institution.
However, eyes are slightly easier to analyze than teeth or horns, says Hughes, because the visual system has only one function: vision. “We knew it was the eye from the temple,” he says, so it makes sense that the connecting filament is a nerve. “I think this was convincingly debated in the papers.” Why trilobites need so much visual power remains a mystery.
The X-ray images were taken by Wilhelm Stürmer, a professional radiologist and amateur paleontologist from Siemens. In the 1970s, Stormer mounted an X-ray probe in his Volkswagen bus and discovered a new method for studying fossils: X-ray paleontology, which allowed him to view the hard rock at the site and take some of the most complex fossil images. that. day.
Researching Hunsrück Slate, a fossil quarry a short drive from his home in Munich, Germany, Stürmer discovers a world of fossil creatures embedded in rock. Remarkably, these specimens – including the phacopid trilobites – are so well preserved that the soft tissue is visible. Stormer and his collaborator Jan Bergstrom noted that the trilobites appeared to have fossilized “fibers” attached to their compound eyes, which they described in the June 1973 issue of the journal. digging magazine.
Related: In the picture: A Cambrian creature eats a filter
When Stormer showed the findings to other paleontologists, Scheunemann said, “his colleagues in the scientific world laughed at him.” The prevailing wisdom at the time was that soft tissues, such as nerves, did not harden. According to Scheunemann, his critics argued that Stormer had abused the gill sutures for the optic nerve tissue. However, the radiologist remained steadfast in his belief.
“Stormer believed his theory until his death, bitterly in 1986,” Scheunemann said. Nearly half a century later, Scheunemann and his team feel that they have finally validated his work.
Unfortunately, like Wilhelm Stürmer, the vacoped trilobites are no longer with us – they went extinct about 358 million years ago at the end of periode DevonAlong with about 75% of life on Earth, Scheunemann said. “But certainly not because of their highly developed and adaptive eyes.”
Originally published in Live Science.
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