(Chrono-) Genus delimitation

Temporal threshold values (cutoffs)

Based on the study of Jetz et al. (2014), Holt & Jønsson (2014) established a “least disruptive” temporal threshold value (cutoff) of 11.4 Ma for avian genera. This value is very close to the 11.79 Ma genus cutoff established for Corvides (Passeriformes) by Jønsson et al. (2016). 

However, taking into account the considerably younger “least-disruptive” genus cutoff of the Tyranni, which I extracted from the timetree provided by Harvey et al (2020), prompted me to favour a general avian genus cutoff at 10 Ma. 

Since a strict application of the proposed genus cutoff would result in considerable disruption of existing genus circumscriptions, I suggest a generic cutoff tolerance that allows to retain traditional genera as long as they are between 8 Ma and 12 Ma. 

Exemplary genus-level timetree to which a genus cutoff has been applied at 10 Ma. In contrast to other cutoffs, this cutoff is provided with a temporal tolerance frame of four million years, allowing to retain traditionally recognised genera that separated from sister genera between 12 Ma and 8 Ma. 


Harvey MG, Bravo GA, Claramunt S, Cuervo AM, Derryberry GE, Battilana J, Seeholzer GF, McKay JS, O’Meara BC, Faircloth BC, Edwards SV, Peréz-Emán J, Moyle RG, Sheldon FH, Aleixo A, Smith BT, Chesser RT, Silveira LF, Cracraft J, Brumfield RT, and Derryberry EP (2020), The evolution of a tropical biodiversity hotspot, Science 370, 1343-48. (abstract) (hi-res tree)

Holt BG, and Jønsson KA (2014), Reconciling hierarchical taxonomy with molecular phylogenies, Syst. Biol. 63, 1010-17. (free pdf)

Hosner PA, Braun EL, and Kimball RT (2016), Rapid and recent diversification of curassows, guans, and chachalacas (Galliformes: Cracidae) out of Mesoamerica: phylogeny inferred from mitochondrial, intron, and ultraconserved element sequences, Mol. Phylogenet. Evol. 102, 320-330. (abstract)

Jetz W, Thomas GH, Joy JB, Hartmann K, and Mooers AO (2012), The global diversity of birds in space and time, Nature 491, 444-448. (abstract) 

Jønsson KA, Fabre PH, Kennedy JD, Holt BG, Borregaard MK, Rahbek C, and Fjeldså J (2016), A supermatrix phylogeny of corvoid passerine birds (Aves: Corvides), Mol. Phylogenet. Evol. 94, 87-94. (abstract) 

Oliveros CH, Andersen MJ, Hosner PA, Mauck WM, Sheldon FH, Cracraft J, and Moyle RG (2019), Rapid Laurasian diversification of a pantropical bird family during the Oligocene-Miocene transition, Ibis 162, 137-152. (abstract)

Reeve AH, Blom MPK, Marki PZ, Batista R, Olsson U, Edmark VN, Irestedt M, and Jønsson KA (2022) The Sulawesi Thrush (Cataponera turdoides; Aves: Passeriformes) belongs to the genus TurdusZool. Scr. 51, 32-40. (free reading) 

Remsen JV, Powell AFLA, Schodde R, Barker FK, and Lanyon SM (2016), A revised classification of the Icteridae (Aves) based on DNA sequence data, Zootaxa 4093, 285-292. (abstract)