The humble trilobites, helmeted creatures that swam in the oceans hundreds of millions of years ago, hide an extraordinary secret – “hyper eyes” never seen before in the animal kingdom.
By contemplating x-ray Researchers found that a certain species of trilobite — an extinct arthropod closely related to the horseshoe crab — had “compound eyes,” complete with hundreds of lenses, their own neural network for processing and transmitting signals, and multiple optic nerves, according to a new study. 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 known 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 knowledge, trilobites come from the family Phacops had compound eyes that were much larger and more complex than their current arthropod relatives. Each of their eyes (they have one on the left and one on the right) holds hundreds of lenses. With a diameter of almost a millimeter, this primary lens is a thousand times larger than a typical arthropod. Beneath it, like a light bulb in a car headlight, are six (or more) faceted substructures, similar to the typical compound eye, located. “Each of the large phacopid eyes is a hypercomplex eye with up to 200 compound eyes each,” said Brigitte Schoenemann, head of the study, a paleontologist at the University of Cologne, in an email to Live Science.
Trilobites are living beings that have lived since the beginning Cambrian (521 million years ago) to the end of the Permian (252 million years ago) on the ocean floor. Some may be predators that hunt water worms, although most are scavengers or plankton eaters. Remains are often found in limestone cliffs dating from the Cambrian. But despite their presence in the fossil record, scientists still have questions about their physiology and evolutionary history.
To answer some of these questions, the researchers used photo enhancement techniques to examine dozens of stock photos and compare them to current results. By doing so, they also solved a long-standing scientific debate: They confirmed that the mysterious series of “fibers” seen in X-ray images from more than 40 years ago were actually bundles of optic nerves connected to the trilobite’s eye.
“Inferring functions in ancient, extinct organisms is always difficult,” said Nigel Hughes, a trilobite expert at the University of California Riverside who was not involved in the study. In fact, according to Hughes, there are even some strange features in living things that cannot be explained – for example, there is still debate about the function of the narwhal’s long, horn-like teeth, they say. Smithsonian Institution.
However, the eye is slightly easier to analyze than teeth or horns, says Hughes, because the optical system has only one function: seeing. “We know from its structure that it’s an eye,” he said, so it makes sense that the filament attached to it is a nerve. “I think it’s been argued pretty convincingly in the papers.” Why trilobites need so much vision remains a mystery.
The X-rays were taken by Wilhelm Stürmer, a professional radiologist and amateur paleontologist from Siemens. In the 1970s, Stürmer installed an X-ray probe on his VW bus and developed a new method for examining fossils: X-ray paleontology, which allowed him to peer through the solid rock at the site and take some of the most advanced fossil photographs of the fossils. day.
While investigating the slate of Hunsrück, a fossil quarry far from his Munich home, Stürmer discovers a world of fossil creatures embedded in rock. In particular, these specimens – including the phacopid trilobites – are so well preserved that even the delicate soft tissue is visible. Stürmer and colleague Jan Bergström found that trilobites appeared to have fossilized “fibers” connected to their compound eyes, which they described in the June 1973 issue of the journal. Paleontology Journal.
Related: In the picture: a filter -eating Cambrian creature
But when Stürmer presented the findings to other paleontologists, “his colleagues from the science laughed at him,” said Schönemann. The prevailing wisdom at the time was that soft tissues such as nerves were not petrified. Stürmer must have mistaken the gill filaments for optic nerve tissue, his critics argued, Schönemann said. Radiologists, however, stuck to his belief.
“The striker believed in his theory until he died bitterly in 1986,” said Schönemann. After nearly half a century, Schönemann and his team finally feel confirmed.
Unfortunately, phacopid trilobites like Wilhelm Stürmer are no longer with us – they died out about 358 million years ago at the end of the 20th century. periode Devon, along with about 75% of all life on earth, said Schönemann. “But certainly not because of his sophisticated and highly adapted eyes.”
Originally published in Live Science.
