Proposal (927) to South American Classification Committee


Recognize new genus Phyllaemulor for Nyctibius bracteatus and change linear sequence of species in Nyctibiidae



The Rufous Potoo, Nyctibius bracteatus, has long been recognized as an “oddball” among the species in Nyctibiidae, but only recently, Costa et al. (2018) have pulled all of its unusual features together to produce a most convincing argument for separating this species in a new genus. They considered in detail genetics, morphology, behavior, and vocalizations. Regarding genetics, they found that four independent studies (including a recent whole-genome study) recognized bracteatus as the sister to the  Nyctibius species, although within Nyctibius, they found some disagreements among species relationships between those studies. The smaller size and very different plumage had long been recognized, but they showed a difference in iris color hitherto unknown. In their exhaustive study of external morphology and osteology, they found various characters apparently primitive within Nyctibiidae, as well as others shared with one or more caprimulgiform (s.l.) families, including Caprimulgidae, Podargidae, Aegothelidae and Steatornithidae. Among the unique behavioral features were the habit of bracteatus to perch crosswise on thin branches rather that vertically atop stubs or on broad branches, and a curious swaying display in response to disturbance rather than the vertical, immobile position of Nyctibius species. This behavior, in combination with the rufous, white-speckled plumage, gives the impression of a hanging dead leaf swaying in a gentle breeze (the genus name proposed, Phyllaemulor, translates to ”leaf-mimicker” – and it is notable that Steatornis, when spending nights in forest away from their caves, gives a similar display when disturbed and also has similar plumage, most unlike that of Nyctibius! The vocalizations of bracteatus are also unlike those given by Nyctibius species. In sum, I highly recommend accepting the proposal to recognize the genus Phyllaemulor for bracteatus.


The nature of the suite of characters examined suggest that bracteatus represents an early stage in the evolution of Nyctibiidae, rather than a late offshoot (as its usual position as last in Nyctibius might indicate).


If the proposal passes, then this implies endorsement of a change in the linear sequence within the Nyctibiidae, with Phyllaemulor bracteatus listed first by the conventions of sequencing.


Thus, a YES vote on this means placement of bracteatus in the monotypic genus Phyllaemulor and placing before Nyctibius in the linear sequence of genera in the family.  Let’s also take a separate vote simply on changing the linear sequence, regardless of generic limits, because one could vote to retain bracteatus in Nyctibius but still place it first in the sequence.


So, for voting purposes:


A. Recognize Phyllaemulor

B. Modify linear sequence to list bracteatus first (regardless of generic limits)



Costa, T. V. V., B. M. Whitney, M. J. Braun, N. D. White, L. F. Silveira and N. Cleere. 2018. A systematic reappraisal of the Rufous Potoo, Nyctibius bracteatus, and description of a new genus. Journal of Ornithology 159: 367-377.


Gary Stiles, November 2021




Comments from Remsen:YES to A and thus also to B.  Costa et al. presented overwhelming evidence, in my opinion, that bracteatus is such an outlier in the family that it merits its own genus; this is an exceptionally good paper.  I like the etymology of the new genus name, too.  The remarkable similarity in plumage pattern between this species and Steatornis is extremely intriguing to me and is best explained by a plumage feature present in some common ancestor of these two lineages, i.e. a rare example of a plumage feature with true phylogenetic significance.  However, I’m off in search of a phylogenetic analysis that including not just Steatornis and Nyctibius but also bracteatus, and to check what were used as outgroups in the existing genetic analyses.  After reading Costa et al., my question is … could bracteatus be closer to Steatornis than to Nyctibius?”


Comments from Robbins: “YES both to placing bracteatus in a new genus (I also like that new name) and to a change in the linear sequence.


Comments from Pacheco: “YES. Distinctions in morphology and behavior, corroborated by data from genetics and vocal repertoire, support A and B options: an exclusive genus treatment and a new linear sequence on the family.”


Comments from Claramunt: “YES. I was skeptical initially as the creation of a new genus is not needed in this case (e.g. for solving a phylogenetic problem), with the additional drawback that the new genus is monotypic. But then, considering the distinctiveness of bracteatus, the separation in a new genus makes sense.”


Comments from Bonaccorso: “A and B. YES. The combination of morphological, molecular, and behavioral evidence is overwhelming. Thus, I support recognizing Phyllaemulor and modifying the linear sequence.”


Comments from Zimmer: “YES & YES, for all of the reasons presented in Costa et al (2018), and nicely summarized by Gary in the Proposal.  I would echo others in applauding the etymology of the new genus name.”