A groundbreaking study by paleontologists at Yunnan University reveals that two Myrodonidae fish species, which thrived in what is now China approximately 518 million years ago during the Cambrian period, possessed a unique vision system featuring two large lateral eyes alongside two smaller central eyes.
An artist’s reconstruction of the four-eyed Myllokunmingiid that navigated the ancient world. Image credit: Xiangtong Lei and Sihang Zhang.
This primitive jawless fish, known as Myllokunmingiid, existed during the Cambrian period, a time marked by rapid evolutionary advancements in body structures and sensory systems as a response to increased predation.
Considered the oldest known vertebrates, these fascinating creatures challenge our understanding of early vision.
In a recent study, Professor Peiyun Cong and colleagues investigated a newly discovered fossil of Myrocunminidae, expertly preserved at the renowned Sumjiang Fossil Bed in southern China.
“These fossils maintain remarkable detail in their eye structures,” stated Professor Cong.
“Initially, we focused on the large eye to outline its anatomy and were astonished to discover two fully functional small eyes nestled between them. The excitement of this finding was immense.”
Modern vertebrates primarily rely on two eyes for vision.
The pineal gland, a brain structure, plays a crucial role in sleep regulation by producing melatonin in response to light exposure.
Interestingly, some fish, amphibians, and reptiles retain the ability to detect light through what is commonly referred to as a “third eye.”
The discovery of two Myrocunminidae provides evidence that early vertebrates possessed a well-developed pair of image-forming eyes, rather than a simple light sensor.
“Our findings suggest that the pineal gland originated as an imaging eye,” remarked Professor Cong.
“Over time, these structures diminished in size, lost their vision capabilities, and assumed their modern function in sleep regulation.”
Using a high-powered microscope, researchers identified melanosomes—pigment-containing organelles crucial for vision—across all four Myrocunminidae orders.
Chemical analyses confirmed the presence of melanin, the same pigment utilized in contemporary vertebrate vision.
Circular formations resembling lenses indicate that these eyes had the capacity to detect light and form images, offering direct evidence of an advanced visual system in early vertebrates.
Professor Sarah Gabot from the University of Leicester emphasized, “Fossilized eyes are extremely rare. It’s remarkable that delicate structures like eyes can survive hundreds of millions of years.”
“However, under optimal conditions, such preservation is achievable, unveiling crucial insights into how extinct species perceived their environment.”
“We speculated that these Chinese fossil eyes might be remarkably preserved, demonstrating light-absorbing pigments in their retinas and lenses, revealing the visual acuity of our early ancestors.”
The Cambrian seas presented perilous conditions, with emerging large predators threatening the small, vulnerable early vertebrates.
Dr. Jacob Binther, a paleontologist at the University of Bristol, noted, “In such an environment, having four eyes may have provided these organisms with a broader field of vision essential for evading predators.”
This discovery elucidates long-held questions about the origin of the pineal gland, offering the oldest known evidence of a camera-like eye in the fossil record.
“This finding reshapes our understanding of vertebrate evolutionary history,” stated Dr. Binther.
“It turns out our ancestors were visually sophisticated beings capable of surviving in a hazardous world.”
The study also prompts a reevaluation of the established notion of the vertebrate “third eye.”
“These early vertebrates possessed not only a third eye, but intriguingly, a fourth eye as well,” concluded Dr. Binther.
This discovery is detailed in a paper published in the journal Nature on January 21, 2026.
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X Ray others. 2026. Four camera-shaped eyes found in the earliest Cambrian vertebrates. Nature 650, 150-155; doi: 10.1038/s41586-025-09966-0
Source: www.sci.news
