What is in a genus name? Conceptual and empirical issues preclude the proposed recognition of Callibella...

In a recent article, Silva et al. (Zool Scr 47:133-143, 2018) proposed the relocation of the dwarf marmoset, Mico humilis, to the so far unrecognized genus Callibella. We contend that a taxonomic scheme that recognizes Callibella as if it were a valid genus is inadequately supported, and to some extent contradicted, by the ecological and morphological information provided by the authors. We discuss why the criterion of sympatry, invoked by Silva et al. to justify the recognition of Callibella at the genus level, is uninformative for taxonomic decisions above the species level. We also show that the morphological characteristics used by Silva et al. to separate Mico humilis from the other Mico are individually variable and present in every analyzed species of the genus. Moreover, we demonstrate that the Evolutionarily Distinct and Globally Endangered (EDGE) metric, employed by those authors to attempt to justify their taxonomic proposition, makes no sense in a taxonomic context. Conceptually, the use of autapomorphies and plesiomorphies to justify using Callibella goes against one of the main objectives of a meaningful classification, that is, to allow for all kinds of inferences based on previous observations (i.e., to be inductively projectible). Based on these arguments, we demonstrate that regarding Callibella as a subgenus of Mico is the most suitable way of making the Linnean taxonomy of marmosets congruent with the phylogenetic information available for the group.