Groundbreaking research from Yale's invertebrate paleontology department used innovative new methodology created by my sister, Victoria McCoy, to test the eyesight of an extinct monster. And turns out that pterygoid eurypterids, as these huge sea scorpions* are known, failed their "post-extinction eye exam:" they had terrible vision!

Thus, eurypterids have been demoted from their former position as top predator of Paleozoic seas: instead, they likely preyed upon relatively weak and soft-bodied organisms. (Not only is their vision too poor for them to be top predators, but previous research suggested that their claws were too weak to puncture the shells and exoskeletons of armored prey). In fact, the only living creature they likely could have killed is the not-so-fearsome sea slug.

I spoke briefly with my sister. to whom I've given the nickname "Prehistoric Eye Doctor." She told me:

"there are two problems inherent in studying the eye structure of fossilized arthropods, and thus their visual system. These are 1. The lack of soft internal structures, and 2. The loss of the initial 3D shape of the eye. The first problem cannot be resolved with our current eurypterid fossils. However, the second can be addressed by treating a flattened fossil as a 2D projection of the initial 3D eye. That's what we did in this project to understand how the lenses are oriented relative to each other."

Tory's use of a mathematical projection uncovered the angle between the two lenses of the eurypterid's eye; a smaller angle makes for better eyesight. However, the Yale team's results suggest these huge sea creatures had poor vision, and were probably scavengers that searched for food in the dark. Her methodology, and the results of this paper (coauthored by Victoria McCoy, Derek Briggs, Ross Anderson, and Maria McNamara) have far-reaching utility for interpreting the eyesight of extinct creatures and reconstructing past ecosystems.

Perhaps most importantly, the world can breathe a collective sigh of relief: these giant scorpions, perhaps the creepiest and most terrifying creatures of all time, had at least one flaw!

*It is worth noting that eurypterids were not actually scorpions, despite their analagous body form. However, looking at modern analogues to eurypterids, such as scorpions, has proven quite fruitful: