Note: "Pan-clades"

In systematics one must distinguish between crown clades and total clades. While total clades include all extant and all extinct members of a given clade, crown clades comprises just the last common ancestor of the extant representatives of that clade and all its descendants. In other words, crown clades do not encompass representatives of the stem group. 

The demand for a clear distinction between crown clades and total clades poses the question how to separate them taxonomically. Creating entirely new names for total clades according to the Principle of Priority, as both ICZN and ICPN suggest or tolerate (Louchard et al., 2013; de Queiroz, 2007; Cantino & de Queiroz, 2020; de Queiroz et al., 2020), might lead to a plethora of new and entirely different names for intimately related clades.

Therefore, I strongly favour the proposal of Lauterbach (1989, in German) to simply add the hyphenated prefix "pan-" to the crown-clade name to create an informal taxonomic name for the total clade, like pan-Aves. In my view, this rule should be applied rigorously, without exceptions. 

In their paper on Strisores, Chen & Field (2020) suggest the total-clade names Pan-Trochilidae and Pan-Apodiformes for the respective crown clades, but for the total clade of the crown clade Strisores they propose the name Caprimulgimorphae, instead of Pan-Strisores. Although conforming to the PhyloCode, this approach should not be accepted by the ornithological community.  


References

Cantino PD, and de Queiroz K (2020), International code of phylogenetic nomenclature (PhyloCode), version 6. www.phylonames. org. (link)

 

de Queiroz K (2007), Toward an integrated system of clade names. Syst. Biol. 56, 956-974. (pdf)

 

de Queiroz K, Cantino PD, and Gauthier JA (2020), Phylonyms - A companion to the PhyloCode. CRC Press, Boca Raton, FL, USA(link)


Haug C, and Haug JT (2015), The ambiguous use of the prefix 'Pan' in arthropod systematics, RRJZS 3, 19-24. (pdf)


Joyce WG, Anquetin J, Cadena EA, Claude J, Danilov IG, Evers SW, Ferreira GS, Gentry AD, Georgalis GL, Lyson TR, Perez-Garcia A, Rabi M, Sterli J, Vitek NS, and Parham JF (2021), A nomenclature for fossil and living turtles using phylogenetically defined clade namesSwiss J. Palaeontol. 140: 5.  (pdf)


Lauterbach KE (1989), Das Pan-Monophylum: Ein Hilfsmittel für die Praxis der phylogenetischen Systematik, Zool. Anz. 223, 139-156. 

 

Louchart A, Viriot L, and Dubois A (2013), The use of the prefix Pan- and other problems in zoological family-level nomenclature, Zootaxa 3750, 197-200. (pdf)


Meier R, and Richter S (1992), Suggestions for a more precise usage of proper names. Ambiguities related to the stem lineage concept, J. Zool. Syst. Evol. Res. 30, 81-88.