The Synthetonychiidae are a small family of harvestman with a handful of species in a single genus.

Species in this family are between one and two millimeters long, with legs up to almost six mm.

[2] All described species occur only on New Zealand.

[2] Synthetonychiidae seem to be closely related to the Triaenonychidae from the Australian region.

[2] The name of the type genus is combined from Ancient Greek synthetos "compounded" and onychion, the diminutive of onyx "claw".