Remsenornis, Piacentini, 2017

Piacentini, Vítor De Q., 2017, A new genus for the Blue-and-yellow Tanager (Aves: Passeriformes): a suggested adjustment to the classification of the Thraupidae, Zootaxa 4276 (2), pp. 293-300 : 298-299

Remsenornis gen. nov.

Type species: Loxia bonariensis Gmelin, 1789 (traditionally treated as Thraupis bonariensis or, most recently, Pipraiedea bonariensis ).

Included taxa: Remsenornis bonariensis darwinii ( Bonaparte, 1838) , R. b. compositus ( Zimmer, 1944), R. b. schulzei ( Brodkorb, 1938) and R. b. bonariensis ( Gmelin, 1789) .

Diagnosis. The adult male plumage of Remsenornis differs from all other genera of the Thraupidae by the combination of a well-defined blue hood with a bright yellow or orange-yellow rump. It further differs from Pipraeidea , its sister lineage, in all points highlighted above.

Etymology. I am happy to name this new genus after James V. "Van" Remsen, Jr., in recognition of his contribution to Neotropical and, especially, South American ornithology. Van has helped form the careers of many ornithologists over the years, but his influence has reached far beyond his formal students, which includes, for example, my views on the curation and care of bird collections. My ideas on generic limits of birds and the meaning and value of monospecific genera also overlap broadly with Van’s, and such ideas are particularly relevant to this paper.

Gender: masculine.

Remarks. The establishment of a monospecific genus for the Blue-and-yellow Tanager may be questioned on the grounds that monospecific/monotypic genera do not convey information regarding systematic relationships when cited in a linear sequence (or when the species are presented in a book). One of the many flaws of such criticism stems from a misconception of the true goals of a linear sequence, coupled with a limited view of the reasons behind the existence of monospecific genera. It is worth keeping in mind the distinction between mono/ polyspecific (i.e. single/many species) and mono/polytypic (i.e. single/many “forms” [taxa]).

First, it should be clear that a linear sequence of taxa is not intended to represent sistership of species (that is left to phylogenies, of course). Linear sequences are a simple and succinct way to present taxonomic diversity in a text. Second, a monospecific genus may result from different processes: (1) the existence of a very distinct lineage/ species that may have undergone strong evolutionary pressures (unlike its sister lineage/species); (2) it may result from extinction(s) of closely related/sister lineages/species; (3) it may reflect our ignorance of the existence of other congeneric species, e.g. Doliornis was treated as a monotypic genus for over a century, until the discovery of a second Doliornis species; (4) it may reflect a temporal trend on the classification of the taxa included in it: for instance, Remsenornis is here defined as a monospecific but polytypic (i.e., with more than one “form”[taxon]) genus which may become polyspecific when any of the subspecies is elevated to species level—a likely fate for R. b. darwinii once adequate data becomes available, and a treatment already adopted by del Hoyo et al. (2016). Some of the points raised above on the significance of monospecific genera were also presented by Isler et al. (2013).

In any event, the treatment proposed here is far from being a novelty within the Thraupidae . Currently, there are at least nine other cases of two sister species being treated in two distinct, monospecific genera (following Burns et al. 2016): Orchesticus vs. Parkerthraustes ; Sericossypha vs. Compsothraupis ; Chlorophanes vs. Iridophanes ; Eucometis vs. Trichothraupis ; Piezorina vs. Xenospingus ; Urothraupis vs. Nephelornis ; Spodiornis vs. Acanthidops ; Idiopsar vs. Chionodacryon ; and Diuca vs. Gubernatrix . The latter pair is even known to hybridize in the wild, which is not the case for Pipraeidea melanonota and Remsenornis bonariensis .

Despite the subjectivity of generic limits, the recognition of Remsenornis brings more consistency to classification of the Thraupidae—either the traditional or the one proposed by Burns et al. (2016), which I strongly support. Additional minor adjustments may still be proposed, but I believe we are close to a robust and—hopefully—stable classification of the tanagers.