Tetrophthalmi is an extinct suborder of Opiliones (commonly known as harvestmen or daddy longlegs) that had four eyes. First described in 2014, it is known from two extinct species. Phylogenetic analysis suggests that four eyes is the ancestral condition for harvestmen, placing Tetrophthalmi and Cyphophthalmi in a basal position within Opiliones.

Tetrophthalmi is an extinct suborder of Opiliones (commonly known as harvestmen or daddy longlegs) that had four eyes. First described in 2014, it is known from two extinct species. Phylogenetic analysis suggests that four eyes is the ancestral condition for harvestmen, placing Tetrophthalmi and Cyphophthalmi in a basal position within Opiliones.