The feather mite genus Lamellodectes Hernandes and Valim, 2014 (Proctophyllodidae) was originally referred to the subfamily Pterodectinae based on the crucial diagnostic feature of this subfamily—the fusion of the epigynum with epimerites IIIa in females. Detailed investigation of two Lamellodectes species collected from ovenbirds (Passeriformes: Furnariidae) in Costa Rica has shown that this genus is actually close to Platyacarus Kudon, 1982 (Proctophyllodinae). Both genera have 4 ventral setae (ra, wa, la, and s) on tarsi I and II, while other proctophyllodid genera have only 3 setae (ra, wa, la). Additionally, it was found that the fusion of epigynum with epimerites IIIa in females of Lamellodectes is incomplete, as in some representatives of the proctophyllodine genera Anisophyllodes Atyeo, 1967 and Armophyllodes Mironov and Bermúdez, 2018 that gives evidence this character state has been independently developed in this genus. Herein, the genus Lamellodectes is provided with renewed diagnosis and transferred to the subfamily Proctophyllodinae; one new species, Lamellodectes favus Mironov sp. n., is described from Premnoplex brunnescens (Sclater, PL, 1856) (Passeriformes: Furnariidae) in Costa Rica.