''Schmidtiellus'' is an extinct genus of holmiid

trilobite Trilobites (; meaning "three-lobed entities") are extinction, extinct marine arthropods that form the class (biology), class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most succ ...

s from the

Cambrian The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...

of Poland. As of 2017, a ''Schmidtiellus reetae'' fossil from 530 mya, collected in Saviranna in northern Estonia, is the oldest known fossilized eye. The structure is similar to the

compound eye A compound eye is a Eye, visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidium, ommatidia, which are tiny independent photoreception units that consist of a cornea, lens (anatomy), lens, and p ...

s of modern-day dragonflies and bees, but with (~100)

ommatidia The compound eyes of arthropods like insects, crustaceans and millipedes are composed of units called ommatidia (: ommatidium). An ommatidium contains a cluster of photoreceptor cells surrounded by support cells and pigment cells. The outer part ...

with lenses spaced further apart. There are no lens structures on the top of the eye, so their vision only extends about 25-30 degrees above them.

References

Cambrian trilobites Olenelloidea Fossil taxa described in 1906 {{Redlichiida-stub