Cnemarchus Explained

Cnemarchus is a genus of South American birds in the tyrant flycatcher family Tyrannidae.

The two member of this genus are elongated, upright-perching flycatchers that share similar tail patterns. They are found at high-altitudes.

Taxonomy

The genus Cnemarchus was introduced in 1905 by the American ornithologist Robert Ridgway with the red-rumped bush tyrant as the type species. The name combines the Ancient Greek knēmos meaning "mountain-slope" with arkhos meaning "ruler" or "chief".^[1]

This genus formerly contained only the red-rumped bush tyrant. Molecular phylogenetic studies published in 2020 found that the red-rumped bush tyrant was a sister to the rufous-webbed bush tyrant in the monotypic genus Polioxolmis. The two species had diverged around 4.5 million years ago.^{[2] [3]} Based on these results, the genus Polioxolmis was merged into Cnemarchus placing both species in the genus Cnemarchus.^{[4] [5]}

The genus therefore contains the following two species:^[5]

• Red-rumped bush tyrant (Cnemarchus erythropygius)
• Rufous-webbed bush tyrant (Cnemarchus rufipennis)

Notes and References

1. Ridgway . Robert . Robert Ridgway . 1905 . Descriptions of some new genera Of Tyrannidae, Pipridae, and Cotingidae . Proceedings of the Biological Society of Washington . 18 . 207–213 [208] .
2. Chesser . R.T. . Harvey . M.H. . Brumfield . R.T. . Derryberry . E.P. . 2020 . A revised classification of the Xolmiini (Aves: Tyrannidae: Fluvicolinae), including a new genus for Muscisaxicola fluviatilis . Proceedings of the Biological Society of Washington . 133 . 1 . 35–48 . 10.2988/20-00005 . 229241271 .
3. Ohlson . J.I. . Irestedt . M. . Batalha Filho . H. . Ericson . P.G.P. . Fjeldså . J. . 2020 . A revised classification of the fluvicoline tyrant flycatchers (Passeriformes, Tyrannidae, Fluvicolinae) . Zootaxa. 4747 . 1 . 167–176 . 10.11646/zootaxa.4747.1.7 . 32230123 . free .
4. Web site: Areta . Nacho . Pearman . Mark . September 2020 . Proposal 885: Revise the generic classification of the Xolmiini . South American Classification Committee, American Ornithologists' Union . 26 July 2021.
5. Web site: Gill . Frank . Frank Gill (ornithologist) . Donsker . David . Rasmussen . Pamela . Pamela Rasmussen . July 2021 . Tyrant flycatchers . IOC World Bird List Version 11.2 . International Ornithologists' Union . 26 July 2021 .