Halford, D.A. (21 August 1990), Six new species of Hedyotis L. (Rubiaceae) from Northern Australia. Austrobaileya 3(2): 203-204, Figs 1E-H, 4A, Map 1 [tax. nov.]

• Type: "Northern Territory. DARWIN AND GULF DISTRICT: 6 km NE of Cape Crawford Roadhouse towards Borroloola, 16°38'S, 135°46'E, 30 April 1989, D.Halford H93 (holo: BRI; iso: DNA,K,PERTH)."

• Etymology: The specific epithet refers to the clay soils in which this species commonly grows.

Koch, B.L. & Halford, D.A. in Wheeler, J.R. (ed.) (1992), Hedyotis. Flora of the Kimberley Region: 915, Fig. 282A [secondary reference]

Halford, D.A. (9 September 1992), Review of the genus Oldenlandia L. (Rubiaceae) and related genera in Australia. Austrobaileya 3(4): 698 [basionym]

basionym of: Oldenlandia argillacea (Halford) Halford legitimate

Western Australian Herbarium (2011), FloraBase: the Western Australian Flora Version 2.6: - [nomenclatural synonym]

nomenclatural synonym of: Oldenlandia argillacea (Halford) Halford legitimate

Gibbons, K.L. (June 2020), Hedyotis, Oldenlandia and related genera (Rubiaceae: Spermacoceae) in Australia: New genera and new combinations in an Asian-Australian-Pacific lineage. Taxon 69(3): 531-532 [secondary reference]

• Type: "Holotype: Northern Territory, Darwin and Gulf District: 6 km NE of Cape Crawford Roadhouse towards Borroloola, 30 Apr 1989, Halford H93 (BRI barcode BRI-AQ0500624!; isotypes: DNA barcode D0061322 [image!]; K barcode K000760503 [image!] PERTH barcode PERTH 01625071 [image!])"

Gibbons, K.L. (June 2020), Hedyotis, Oldenlandia and related genera (Rubiaceae: Spermacoceae) in Australia: New genera and new combinations in an Asian-Australian-Pacific lineage. Taxon 69(3): 531 [basionym]

basionym of: Dolichocarpa argillacea (Halford) K.L.Gibbons legitimate

---