Xanthocyparis

Xanthocyparis (synonym Callitropsis) is a genus of cypresses in the family Cupressaceae, comprising one species native to North America and one native to Vietnam in southeast Asia.
Nomenclature and circumscription.
In 2002, Aljos Farjon and others described the new genus "Xanthocyparis" to accommodate the new Vietnamese species "X. vietnamensis" and another species, "X. nootkatensis", the Nootka cypress, which had been formerly included in the genus "Chamaecyparis" as "C. nootkatensis". This was based in part on the discovery that "C. nootkatensis" was more closely related to the genus "Cupressus" than to "Chamaecyparis".
In 2004, Damon Little and others, while confirming the above relationship with further evidence, pointed out that as circumscribed by Farjon "et al.", "Xanthocyparis" included the type species of "Callitropsis" ("Cupressus nootkatensis", a synonym of "Chamaecyparis nootkatensis" and "Xanthocyparis nootkatensis"). "Callitropsis" had been described by Anders Sandøe Ørsted in 1864, but this name had been overlooked by Farjon and most other authors; under the rules of the International Code of Botanical Nomenclature, "Callitropsis" as the earlier-published name had nomenclatural priority over "Xanthocyparis" if that genus included "Cupressus nootkatensis". Little "et al." therefore recognized "Xanthocyparis" as a synonym of "Callitropsis". The name "Xanthocyparis" was proposed for conservation over "Callitropsis", a decision that was ratified at the International Botanical Congress in 2011.
Little "et al." also presented evidence that "Cupressus" is paraphyletic with respect to "Juniperus" and "Xanthocyparis", with the North American species of "Cupressus" being more closely related to "Xanthocyparis" than they are to the European and Asian "Cupressus" species. These species were transferred to ""Callitropsis" by Damon Little in 2006, although this transfer was not universally accepted. In 2009, most of the North American species previously included in "Callitropsis"" were placed in a separate genus, "Hesperocyparis".