Scientific American has a story about trilobite eyes. In a 429 million year old fossil trilobite fossil, scientists from the University of Edinburgh in Scotland got a glimpse at how the world looked to these ancient animals. A remarkably preserved specimen of Aulacopleura koninckii showed that these animals had eyes that were about as good as today's bees and dragonflies, which have some of the best vision among arthropods. The paper was published in the journal Nature.
Perfectly pristine fossils might make great museum showpieces, but they are not always the most informative for paleontologists. Some of the more salient secrets of ancient life are locked inside fossils, and lucky breaks can reveal internal details that may otherwise remain hidden. In the case of one particular 429-million-year-old trilobite—an extinct arthropod that looked like a big version of a wood louse—a crack in just the right place has allowed paleontologists to see the world through the creature’s eyes.
Trilobites are one of evolution’s greatest success stories. These early animals, characterized by the “three lobes” of their exoskeletal body, first appeared about 521 million years ago, during the biodiversity spike called the Cambrian explosion. They proliferated for millions of years more, ranging from sizes smaller than a button to bigger than a dinner plate, before going extinct about 252 million years ago. And given how common trilobites were in ancient seas, studying their evolutionary history can offer deep insights into life in our planet’s oceans.
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“For a long time, it was thought that just bones, teeth and other hard objects could be preserved in the fossil record,” she says. “To be able to distinguish cellular structures, especially in the eyes, is very, very rare and exceptional.”
Schoenemann and her co-author Euan Clarkson of the University of Edinburgh in Scotland published their analysis of the ancient eye on Thursday in Scientific Reports. Despite being 429 million years old, the trilobite has a modern-looking eye that resembles those of today’s bees and dragonflies. This type is called an apposition compound eye, meaning each lens acts independently to create a mosaic image of what a creature sees.
The detailed look at the trilobite’s eye helps track the evolution of eyes and vision in arthropods over time, says University of New England paleontologist John Paterson, who was not involved in the new study. “The take-home message appears to be that trilobites had developed apposition compound eyes during the earliest evolutionary stages of the group and stuck with this design throughout their history.”
