A research team at Yunnan University has found that the earliest known vertebrates from the Cambrian Period may have possessed "four camera-type eyes", offering new insights into the early evolution of the vertebrate visual system.

The study, published recently in the scientific journal Nature, focuses on jawless vertebrates called myllokunmingids that lived about 518 million years ago. Researchers found that these animals had a dorsal pineal complex on top of their heads with imaging capabilities similar to those of their lateral eyes.

The research was led by Xu Xing, an academician at the School of Life Sciences of Yunnan University, and Cong Peiyun, a researcher at the university's Institute of Paleontology. The team analyzed newly collected fossil specimens of two myllokunmingid species from the Chengjiang biota in Yunnan province.

The fossils preserved a smaller pair of round, dark structures located between the pair of lateral eyes. The researchers confirmed that these structures, like the lateral eyes, were preserved as organic carbon films and contained melanin-bearing melanosomes. Their morphology and size closely match those found in the retinal pigment epithelium of living vertebrates.

More importantly, they also identified traces of lenses within these structures. Their position and size are consistent with the anatomical relationship between the lens and retina in camera-type eyes, indicating that they likely had image-forming functions.

According to Yunnan University, the discovery expands our understanding of the origin and early evolution of the vertebrate visual system and offers a fresh perspective on animal survival strategies during the Cambrian explosion.