A new specimen of Lacinius Thorell, 1876; (Opiliones: Phalangiidae) from Eocene Baltic amber is described. We interpret it as conspecific with a slightly younger record from the German Bitterfeld amber, originally referred to as the extant species L. erinaceus Staręga, 1966. Our new specimen reveals pedipalpal apophyses on both the patella and the tibia, features which we can now confirm in the Bitterfeld fossil too. This unique character combination for the genus justifies a new, extinct species: Lacinius bizleyi sp. nov. The Baltic amber inclusion dates to ca. 44–49 Ma, and is thus the oldest putative example of Lacinius in the fossil record. It is a further example of an arachnid species shared between Baltic and Bitterfeld amber.