Erbenochile

Erbenochile is a genus of spinose phacopid (acastid) trilobite found in Lower to Middle Devonian age rocks from Algeria and Morocco. Originally described from an isolated pygidium, the first complete articulated specimen of E. erbeni revealed the presence of extraordinarily tall eyes:

""Straight-sided towers of lenses... with [upto] 18 lenses in a vertical file""

- Fortey & Chatterton (2003)

Number of lenses has been estimated at 560 or 450 incomplete preservation accounting for the uncertainty. A lens count of 18 lenses per file is unusually high (twice that of closely related genus) and accounts for the height of the eye, as opposed to a noticeable increase in the size of the individual lenses. A recently found undescribed species of Erbenochile has smaller eyes, with fewer files (33-35) and fewer lenses per file (15 max) than E. erbeni. E. erbeni eyes allow full 360 degree coverage in the horizontal plane and were high enough to allow the trilobite to see backwards over its thorax. The presence of eye shades, blocking glare from over head, validates the suggestion that (at least some) trilobites were diurnal and not nocturnal,

""a detail of life habit which had previously been equivocal: Eyeshades are no use in the dark.""

- Fortey & Chatterton (2003)