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Cyanocorax is a genus of New World jays, passerine birds in the family Corvidae. It contains several closely related species that primarily are found in wooded habitats, chiefly in lowland tropical rainforest but in some cases also in seasonally dry forest, grassland and montane forest. They occur from Mexico through Central into southern South America, with the green jay and brown jay just entering the United States in southernmost Texas, and the azure and plush-crested jays occurring southwards to the lower Paraná River basin. This genus is considered especially close to Cyanolyca, an upland radiation occurring throughout the American Cordillera from Mexico to Peru and Bolivia, who look very similar to the blue-and-black species of Cyanocorax except for being a bit smaller. The North American blue jay genera Aphelocoma, Cyanocitta and Gymnorhinus seem to be slightly less closely related.
The genus Cyanocorax was described by the German zoologist Friedrich Boie in 1826, with the plush-crested jay as the type species. The generic name is derived from the Ancient Greek words κυανος (kuanos), meaning "dark blue", and κοραξ (korax), meaning "raven".
Systematics and evolution
With the merge of the formerly separate genera Calocitta (the two magpie-jays) and Psilorhinus (brown jay) into Cyanocorax, the genus now contains around 20 species:
The expanded genus Cyanocorax can be neatly divided into two clades, the first containing the former Calocitta and Psilorhinus, as well as the South American lineage which was historically treated as genus Uroleucus. The other clade unites the remaining South American species with the group formerly separated as Cissilopha, as well as the Inca jay group which are the only members of the genus to have conspicuous carotenoid (yellow/green) pigments in their plumage; though there is deep genetic divergence between the two taxa as well as differences in their plumage, habitat, behaviour, and calls.)|| Azure-naped jay || Brazil, Colombia, and Venezuela
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|C. cayanus group: eastern (Atlantic) South America
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|160px || Cyanocorax cayanus || Cayenne jay || Brazil, French Guiana, Guyana, Suriname, and Venezuela
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|160px || Cyanocorax chrysops || Plush-crested jay || southwestern Brazil, Bolivia, Paraguay, Uruguay, and northeastern Argentina
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|160px || Cyanocorax cyanopogon|| White-naped jay || Brazil
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Evolution
The fossil corvid Protocitta dixi, described from Middle Pleistocene (Illinoian, Penultimate Glacial Period, roughly 150.000 years ago) remains found in a former cave near Reddick, Florida, was described as similar to both Calocitta and Psilorhinus lineages. Although no cladistic analysis was conducted, at least qualitatively it was assessed as less closely related to the Holarctic magpies, who are a member of the "monochrome" radiation of crows and ravens, so it is very likely that Protocitta was indeed a prehistoric American blue jay. No Cyanocorax is attested from anywhere near Florida however, and since Protocitta was not compared to the North American radiation of blue jays, it is at least as likely to belong with the latter group.