Fossil eyes show wraparound three-dimensional vision, half a billion years ago
Each of our eyes sees a slightly different view of the world, and our brain combines these signals into a single three-dimensional image. But this only works in one direction, because our eyes face straight ahead and their respective fields of vision only overlap in a narrow zone. But there was once a creature that had binocular vision in a massive arc around its body, not just in front but to the sides as well. It’s called Henningsmoenicaris scutula and it lived around half a billion years ago.
H.scutula lived in the Cambrian period, the part of Earth’s history when most of today’s major animal groups exploded into existence. It was a crustacean, one of the earliest members of the group that includes crabs, prawns and lobsters. It was just a millimetre long and almost totally encased within a bowl-shaped shield. From beneath the shield, weird spike-tipped legs propelled it along, while two stalked eyes, each just half a millimetre across, peered out at the Cambrian oceans.
These eyes are compound ones, made up of several units or ‘ommatidia’. They’ve also withstood the test of time. Their organic tissues have since been converted into the mineral apatite, and the resulting fossils perfectly retain the shape and angle of each ommatidium. The eyes are so well-preserved that Brigitte Schoenemann from the University of Bonn could use them to reconstruct how H.scotula saw the world to a “quite impressive degree”.
Each ommatidium points in a slightly different direction and acts like a pixel on a computer screen. The animal used these separate snapshots to construct an overall view of its world. Schoenemann found that each eye is divided into four different areas that face respectively forward, outwards to the side, backwards, and inwards. Together, they cover every direction. The animal’s only blind spot is the bit of space occupied by its own body.
The front-facing parts of the eyes have the highest resolution and overlapping fields of view, just like our own. The outward-facing parts probably scanned the horizon on either side of the animal. The back-facing parts were the most sensitive; they had the biggest ommatidia and would have captured the most light. They might have been angled downwards to scan the dark ocean depths below the animal.
But what about the inward-facing parts? On a normal head, this wouldn’t make any sense, but remember that this crustacean had eyes on stalks. The inward-facing segments had visual fields that overlapped with those of the outward-facing segments on the opposite eye. This animal would have had excellent depth perception all around its body, rather than just in front of it. As Schoenemann puts it, it has “a three-dimensional visual net that covers not only the front, but extends also far to either side”.
But H.scutula could hardly have been described as sharp-sighted. Each ommatidium acts as a single pixel, and each eye had less than 200 of them. These weren’t eyes that could see the world in high-resolution. They were, however, well adapted for detecting movement.
The overlapping visual fields turn the entire space around the animal into a grid of kite-shaped zones (see the diagram above). Any given position in this grid is covered by a pair of ommatidia, one from each eye. As a prey animal moved around, it travelled from one kite to another, and H.scutula could track its whereabouts, distance and direction, even if it couldn’t see its target clearly.
Even though it was lived almost half a billion years ago, this tiny crustacean has a sophisticated set of eyes that allowed it scan the world around it in almost every direction.
Reference: Schoenemann, Castellani, Clarkson, Haug, Maas, Haug & Waloszek. 2011. The sophisticated visual system of a tiny cambrian crustacean: analysis of a stalked fossil compound eye. Proc Roy Soc Bhttp://dx.doi.org/10.1098/rspb.2011.1888
Go Further
Animals
- These 'trash fish' are among Earth's most primitive animalsThese 'trash fish' are among Earth's most primitive animals
- These photos are works of art—and the artists are bugsThese photos are works of art—and the artists are bugs
- The epic migration of a 6-foot long, 200-pound catfishThe epic migration of a 6-foot long, 200-pound catfish
- Frans de Waal, biologist who studied animal emotion, dies at 75Frans de Waal, biologist who studied animal emotion, dies at 75
Environment
- Are synthetic diamonds really better for the planet? The answer isn't clear-cut.Are synthetic diamonds really better for the planet? The answer isn't clear-cut.
- This year's cherry blossom peak bloom was a warning signThis year's cherry blossom peak bloom was a warning sign
- The U.S. just announced an asbestos ban. What took so long?The U.S. just announced an asbestos ban. What took so long?
- The most dangerous job? Inside the world of underwater weldersThe most dangerous job? Inside the world of underwater welders
- The harrowing flight that wild whooping cranes make to surviveThe harrowing flight that wild whooping cranes make to survive
History & Culture
- Meet the powerful yokai that inspired the demon king in ‘Demon Slayer’Meet the powerful yokai that inspired the demon king in ‘Demon Slayer’
- A surprising must-wear for European monarchs? Weasels.A surprising must-wear for European monarchs? Weasels.
- Meet the woman who made Polaroid into a cultural iconMeet the woman who made Polaroid into a cultural icon
- Inside the observatory that birthed modern astrophysicsInside the observatory that birthed modern astrophysics
Science
- LED light treatments for skin are trendy—but do they actually work?LED light treatments for skin are trendy—but do they actually work?
- NASA smashed an asteroid. The debris could hit Mars.NASA smashed an asteroid. The debris could hit Mars.
- Humans really can have superpowers—scientists are studying themHumans really can have superpowers—scientists are studying them
- Why engineers are concerned about aging infrastructureWhy engineers are concerned about aging infrastructure
Travel
- 2024 will be huge for astrotourism—here’s how to plan your trip2024 will be huge for astrotourism—here’s how to plan your trip
- Play and stay in the mountains of eastern Nevada
- Paid Content
Play and stay in the mountains of eastern Nevada - This couple quit the city to grow wasabi in Japan's mountainsThis couple quit the city to grow wasabi in Japan's mountains