proper and the newly identified Tetrophthalmi, while the Phalangida split into Laniatores and the "Palpatores". Finally, the Palpatores diversified into Eupnoi and Dyspnoi. The analysis moves divergence of the extant suborders from the Devonian Period to the Carboniferous. Opiliones' own divergence is dated to 414 million years ago, which arachnid are estimated to have originated during the late Cambrian to early Ordivician. Genetic analysis performed on a modern Phalangium opilio specimen found that a suppressed gene that, if active, would generate a second pair of eyes at the lateral location, providing independent evidence of four eyes being the ancestral condition. Garwood et al. also argue that Carboniferous harvestmen diversification is more consistent with changes observed in other terrestrial arthropods, which have been linked to high oxygen levels during that period. Relationship within suborders Cyphophthalmi The Cyphophthalmi have been divided into two infraorders, Temperophthalmi (including the superfamily Sironoidea, with the families Sironidae, Troglosironidae and Pettalidae) and Tropicophthalmi (with the superfamilies Stylocelloidea and its single family Stylocellidae, and Ogoveoidea, including Ogoveidae and Neogoveidae); however, recent studies suggest that the Sironidae, Neogoveidae and Ogoveidae are not monophyletic, while the Pettalidae and Stylocellidae are. The division into Temperophthalmi and Tropicophthalmi is not supported, with Troglosironidae and Neogoveidae probably forming a monophyletic group. The Pettalidae are possibly the sister group to all other Cyphophthalmi. While most Cyphophthalmi are blind, eyes do occur in several groups. Many Stylocellidae, and some Pettalidae bear eyes near or at the base of the ozophores, as opposed to most harvestmen, which have eyes located on top. The eyes of Stylocellidae could have evolved from the lateral eyes of other arachnids, which have been lost in all other harvestmen. Regardless of their origin, it is thought that eyes were lost several times in Cyphophthalmi. Spermatophores, which normally do not occur in harvestmen, but in several other arachnids, are present in some Sironidae and Stylocellidae. Eupnoi The Eupnoi are divided into two superfamilies, the Caddoidea and Phalangioidea. The Phalangioidea are assumed to be monophyletic, although only the families Phalangiidae and Sclerosomatidae have been studied; the Caddoidea have not been studied at all in this regard. The limits of families and subfamilies in Eupnoi are uncertain in many cases, and are in urgent need of further study. Dyspnoi The Dyspnoi are probably the best studied harvestman group regarding phylogeny. They are clearly monophyletic, and divided into two superfamilies. The relationship of the superfamily