Baron's Spinetail (Cranioleuca baroni) - HBW 8, p. 298

Taxonomy: Siptornis baroni Salvin, 1895, Huamachuco, La Libertad, and Cajabamba, Cajamarca, Peru.
Sister-species to C. antisiensis, and very likely conspecific; although populations at extremes of ranges are clearly different, the two grade into one another in step-clinal manner, making it difficult or impossible to determine to which taxon certain populations should be assigned (see page 187), this applying also to an apparently undescribed population in Amazonas (N Peru); thorough, quantitative analysis of all parameters (including plumage, morphometrics, vocalizations, genetics) required to elucidate the situation with regard to geographical differentiation and speciation. Both form a superspecies together with C. erythrops, C. demissa, C. hellmayri and C. curtata; all share plumage similarities and mostly lower montane distribution, and their close relationship is consistent with recent genetic data. Some authors, however, have considered them to belong to a superspecies that also includes C. subcristata, C. pyrrhophia, C. henricae, C. obsoleta, C. pallida and C. albicapilla, but such a relationship is not supported by recent genetic findings. Size variation among populations of present species substantial but somewhat irregular, correlated strongly with elevation, e.g. in Ancash birds of high elevations in N are much larger than low-elevation ones in S. Moreover, inter-locality variation is extraordinary; virtually every population sample seemingly diagnosable on basis of size and plumage characters, and many at least as distinctive as are currently accepted races. Three subspecies tentatively recognized.