Proposal (451) to South American Classification Committee
Create a new order, Eurypygiformes, for the Sunbittern (and Kagu)
NOTE: The following proposal was submitted to and passed NACC, and is here submitted with the authors’ permission.
Background: The Gruiformes as traditionally recognized are an extremely diverse group, and there have been numerous suggestions that they are not monophyletic. For example, Cracraft (1981) recognized three particularly problematic families whose placement in the Gruiformes was tenuous; two of these taxa (the mesites, Mesitornithidae, and the bustards, Otididae) are still placed in the Gruiformes, whereas the third (the buttonquail, Turnicidae) is now generally recognized as belonging to the Charadriiformes. Additional taxa that are dubiously placed within the Gruiformes include the seriemas (Cariamidae), the Kagu (Rhynochetidae), and the Sunbittern (Eurypygidae).
Using cladistic analyses of morphological characters, Livezey and Zusi (2001, 2007) did not recover a monophyletic Gruiformes, but instead found gruiform taxa spread across their phylogeny, with the Sunbittern, Kagu, bustards, mesites, rails (Rallidae), and sungrebes (Heliornithidae) all falling far outside a “core” Gruiformes consisting of the trumpeters (Psophiidae), cranes (Gruidae), Limpkin (Aramidae), and Hoatzin (Opisthocomidae). They found the Sunbittern and Kagu to be sister taxa, and used the name Eurypygae for a sub-order consisting of these taxa. In contrast, Sibley and Ahlquist (1990) recovered a monophyletic Gruiformes in their DNA-DNA hybridization-based study.
Recent phylogenetic studies based on mitochondrial and nuclear DNA sequences have provided new information on the relationships of these taxa (Fain and Houde 2004, Ericson et al. 2006, Hackett et al. 2008). There is increasingly strong evidence that the traditional Gruiformes is not a monophyletic group. Instead, only five of the nine families traditionally placed in the order (excluding buttonquail) appear to constitute a monophyletic core Gruiformes (cranes, Limpkin, trumpeters, rails, and sungrebes) (Fain and Houde 2004, Ericson et al. 2006, Fain et al. 2007, Hackett et al. 2008).
In both Ericson et al. (2006) and Hackett et al. (2008), the Sunbittern is sister, with strong support (>0.95 posterior probability, 100% bootstrap), to the Kagu (Rhynochetidae). Together these sister taxa appear to represent a relatively ancient lineage that is not closely allied to any other group of extant birds (Fain and Houde 2004, Ericson et al. 2006, Hackett et al. 2008).
Recommendation: We propose that the Check-list recognize the order Eurypygiformes for the Sunbittern (the Kagu, which occurs outside our area, would also be in this order). This name is new, and has been adopted by IOC check-list (Gill et al. 2009). We recommend that the new order be placed immediately before the Gruiformes in the linear classification.
Cracraft, J. 1981. Toward a phylogenetic classification of the recent birds of the world (class Aves). The Auk. 98(4) 681-714.
Ericson, P.G.P., Anderson, C.L., Britton, T., Elzanowski, A., Johansson, U.S., Källersjö, M., Ohlson, J.I., Parsons, T.J., Zuccon, D., and Mayr, G. 2006. Diversification of Neoaves: integration of molecular sequence data and fossils. Biol. Lett. 2 543-547.
Fain, M.G. and Houde, P. 2004. Parallel radiations in the primary clades of birds. Evolution. 58(11) 2558-2573.
Fain, M.G., Krajewski, C., and Houde, P. 2007. Phylogeny of “core Gruiformes” (Aves: Grues) and resolution of the Limpkin-Sungrebe problem. Molecular Phylogenetics and Evolution. 43 515-529.
Gill, F., M. Wright, and D. Donsker, D. 2009. IOC World Bird Names (version 2.0).
Hackett, S.J, Kimball, R.T., Reddy, S., Bowie, R.C.K., Braun, E.L., Braun, M.J., Chojnowski, J.L., Cox, W.A., Han, K., Harshman, J., Huddleston, C.J., Marks, B.D., Miglia, K.J., Moore, W.S., Sheldon, F.H., Steadman, D.W., Witt, C.C., and Yuri, T. 2008. A phylogenomic study of birds reveals their evolutionary history. Science. 320 1760.
Livezey, B.C. and Zusi, R.L. 2001. Higher-order phylogenetics of modern Aves based on comparative anatomy. Netherlands Journal of Zoology. 51(2) 179-205.
Livezey, B.C. and Zusi, R.L. 2007. Higher-order phylogeny of modern birds (Theropoda: Aves: Neornithes) based on comparative anatomy. II. Analysis and discussion. Zoological Journal of the Linnean Society. 149 1-95.
Sibley, C.G. and Ahlquist, J.E. 1990. Phylogeny and classification of birds. Yale. Univ. Press, New Haven, Connecticut.
Shawn Billerman, Irby Lovette, Terry Chesser, August 2010
Comments from Zimmer: “YES. The best available data seem to support this move, although, intuitively, it’s harder for me to accept all the proposed “core” Gruiformes as belonging together.”
Comments from Stiles: “YES – this pairing is well supported and these two families have no close relatives and cannot be maintained in Gruiformes.”
Comments from Pacheco: “YES. Ericson et al. (2006) e Hackett et al. (2008), demonstraram – ainda que sem muita surpresa – que Eurypyga e Rhynochetos constituem juntos um grupo não proximamente relacionado a qualquer outra linhagem vivente de aves. Isto é muito persuasivo!”
Comments from Nores: “YES. The molecular analyses by Ericson et al. (2006) and Hackett et al. (2008) clearly show that these species do not belong to Gruiformes and must be separated. But I do not agree placing them before the Gruiformes; I would place them before the Caprimulgiformes.”
Comments from Jaramillo: “YES. I must admit that these re-arrangements of orders with strong molecular support are absolutely fascinating. We are living in a very interesting time as ornithologists! The data certainly support this move, perhaps irrelevant, but the two are known for their wing flashing displays and strong and relatively unusual patterns on the primaries.”