Discovery of a relict lineage and monotypic family of passerine birds Based on a comprehensive molecular dataset of passerines birds we identified a branch with a single species, the Spotted Wren-babbler Spelaeornis formosus. We suggest that this represents a relict lineage, which we propose should be placed in its own family, Elachuridae. The scientific name Elachura formosa should be used. We analysed of one of the most comprehensive datasets to date of the largest passerine bird clade, Passerida, which comprises c. 36% of the World’s c. 10,500 bird species. We identified 10 primary branches in the tree. One of these primary branches was made up of a single species, the Spotted Wren-Babbler Spelaeornis formosus, which is a small Wren-like bird that occurs in mountains from the eastern Himalayas to southeast China. This species apparently represents an old branch in the large passerine tree, without any close living relatives. There have surely been other relatives on this branch, which have gone extinct. The fact that it resembles wren-babblers and wrens in appearance is either due to pure chance or to convergent evolution, which may result in similar appearances in unrelated species that live in similar environments. We proposed the new family name Elachuridae for this single species. We also suggested that the scientific name Elachura formosa should be used, and the English name be changed to Elachura, to highlight its distinctness. Timaliidae (56) Pellorneidae (69) Leiothrichidae (133) Zosteropidae (128) Sylviidae (70) Pnoepygidae (5) Cettiidae (32) Scotocercidae (1) Erythrocercidae (3) Aegithalidae (13) */* Phylloscopidae (77) Sylvioidea (1240) Pycnonotidae (151) Bernieridae (11) Donacobiidae (1) Locustellidae (59) Acrocephalidae (61) Cisticolidae (159) 85 */ Macrosphenidae (18) Hirundinidae (88) Alaudidae (98) Panuridae (1) Nicatoridae (3) / Remizidae (12) * * (73) Paroidea Paridae (61) 0.78/– / * * (9) Stenostiridae (9) Hyliotidae (4) 0.76/– Muscicapidae (314) Relationships of the primary lineages Turdidae (171) within Passerida (in colour) based on / Cinclidae (5) * * Muscicapoidea (649) mitochondrial cytb and ND2 and Sturnidae (123) Mimidae (34) 0.91/73 nuclear myoglobin, ODC, GAPDH, Buphagidae (2) 0.59/– Troglodytidae (84) LDH and RAG-1. Posterior probabilities /97 Polioptilidae (17) * Certhioidea (140) Certhiidae (28) (PP) and maximum likelihood bootstrap 0.99/79 Sittidae (11) Bombycillidae (3) / Dulidae (1) (MLBS) values are shown at the nodes, * * Bombycilloidea (10) Hylocitreidae (1) 0.70/– Ptilogonatidae (4) in this order; * indicates PP 1.00 or Spelaeornis formosus India Spelaeornis formosus China MLBS 100%. / Regulidae (6) * * / Reguloidea (6) Coerebidae (1) * * Thraupidae (372) Cardinalidae (68) Emberizidae (174) Icteridae (108) Parulidae (115) Emberizidae (174) Calcariidae (6) Fringillidae (219) Motacillidae (67) /89 /74 Passeridae (51) * * (1854) Estrildidae (141) Passeroidea Viduidae (20) Ploceidae (109) Prunellidae (13) Chloropseidae (11) Peucedramidae (1) Irenidae (2) Nectariniidae (143) Dicaeidae (48) Arcanatoridae (3) Promeropidae (2) Chaetopidae Corvidae Laniidae Monarchidae / Rhipiduridae * * Dicruridae Corvoidea Vireonidae Oriolidae 0.03 Campephagidae.