Table 2.

Nomenclature criteria for existing and new NDV genotypes and sub-genotypes^a.

Criterion	Description
1	All existing genotypes (as per Diel et al., 2012a) in the current classes I and II maintain their Arabic and Roman numerals, respectively.
2	The lowercase Latin letter system to name sub-genotypes is replaced by the numerical-decimal system using Arabic numerals.
3	Dichotomous splitting is used at every defining node (at which separation into sub-genotypes is done) using the numerals 1 and 2.
4	Class I sub/genotypes receive a numerical-decimal address (Arabic numerals separated by periods) that starts with the Arabic numeral of the genotype. Further numeration is made using the dichotomous system at every defining node using numerals 1 and 2. (e.g. 1.1 and 1.2).
5	Class II sub/genotypes receive a numerical-decimal address (Roman-Arabic numerals separated by periods) that starts with the Roman numeral of the genotype. Further numeration is made using the dichotomous system at every defining node (separating sub-genotypes) using numerals 1 and 2. (e.g. VII.1 and VII.2) (example in Supplemental Fig. S1).
6	At the higher order (next defining node closer to the tips) within sub-genotype VII.1, for example, the sub-genotypes that are one order higher will become VII.1.1 and VII.1.2. At the next node within sub-genotype VII.2, the two further sub-genotypes will be named VII.2.1 and VII.2.2, respectively (example in Supplemental Fig. S1).
7	If a branch has unresolved topology, low branch support (i.e. there are polytomies or low bootstrap values), or insufficient number of isolates, the viruses within this branch are not assigned to a higher order, and are assigned the name of the lower order until the topology/support/number of the isolates is resolved and all criteria are fulfilled, regardless of the fact that the distnace criterion is met.
8	Newly identified virus diversity (a group of viruses undescribed before) that meets all classification criteria will be classified as new genotype and will receive a subsequent Roman numeral (e.g. currently XXII is the next available) (example in Supplemental Fig. S2, red color).
9	Existing sub-genotypes that fulfill the genotype criteria will not be designated with a new name in order to maintain the ancestral information in their names (examples in Supplemental Fig. S2, green color).
10	If a new sub-genotype of viruses is identified later, but still falls into a higher order within an existing genotype, this new sub-genotype receives the next consecutive numerical address for the respective level of order in the phylogeny to avoid re-numbering all existing sub-genotypes that are of higher order. For example if a new sub-genotype that outgroups VII.1.1 and VII.1.2 is identified but it is still within VII.1, this new sub-genotype will be named VII.1.3 (example in Supplemental Fig. S3).

^aThe names of genotypes and sub-genotypes used in this table do not correspond to the names in the phylogenetic trees presented in the current study. The names in this table were used for demonstration purposes only.