4.6. Amaranthus dubius Mart. ex Thell., Fl. Adv. Montpell.: 203. 1912.

Neotype (designated by Townsend 1974: 471–472):— GERMANY. Herbarium Monacense, ex horto Erlangensis, s.d., s.c. s.n. (M0107382!, image of the neotype available at https://plants.jstor.org/stable/viewer/10.5555/al.ap.specimen.m0107382?loggedin=true).

= Amaranthus tristis var. xanthostachys Moq., Prodr. [A. P. de Candolle] 13(2): 260. 1849 ≡ Amaranthus dubius var. xanthostachys (Moq.) Thell. in Asch. & Graebn., Syn. Mittel-Eur. Fl. 5: 266. 1914.

Neotype (designated by Iamonico 2016c: 104): — UNKNOWN ORIGIN. Herbarium Requien, s.d., s.c. s.n. (P 04021942!, image of the neotype available at http://mediaphoto.mnhn.fr/media/14494899601942MO7c2qCCiZJWunt).

Alien status:― Neophyte, native to South America; it can be considered as casual in Saudi Arabia (Hassan et al. 2022).

Occurrence in Saudi Arabia:― Jizan (Hassan et al. 2022,: 150).

Specimina visa selecta:― SAUDI ARABIA, Jizan, human-made habitat (coastal plain), 5–15 m, 17 Feb 2021, leg. Masrhai et Al-shaye, det. Masrhai, conf. Iamonico (PNUH!, RO!); ibidem (PNUH!, RO!); ibidem (PNUH!, RO!); ibidem (PNUH!, RO!).