The family Anchistioididae Borradaile, 1915 (Decapoda: Caridea) is a synonym of Palaemonidae Rafinesque, 1815 based on molecular and morphological evidence

Several systematic revisions of the superfamily Palaemonoidea Rafinesque, 1815 (Natantia) have been published, with molecular studies complementing morphological examination. Yet, the true systematic positions of two families within the superfamily have remained uncertain, one of these being Anchistioididae Borradaile, 1915, the second being Desmocarididae Borradaile, 1915. We constructed a further phylogeny of Palaemonoidea based on two rnitochondrial and five nuclear markers to resolve this issue. Anchistioides Paulson, 1875 (the sole genus of Anchistioididae) is recovered nested within Palaemonidae Rafinesque, 1815, calling into question the validity of Anchistioididae as a distinct family. We also review the morphological characters that have been used to support family level status of Anchistioides including mouthparts adaptations, telson ornamentation, larval morphology, the presence of an appendix interna on the first pleopod in both sexes, and the mandible with a distally flared molar process. Although the latter two characters appear to be synapornorphic to the genus, we contend that these are ambiguous and not well founded to support the family-level status of the genus. As a consequence, and supported by the phylogenetic results, Anchistioidiclae is herein considered to be a synonym of Palaemonidae.