Belongs within: Anthemideae.
Cotula, buttonweeds, is a mostly Southern Hemisphere genus of composite herbs bearing solitary flower heads that usually lack ray florets on terminal peduncles. Cotula coronopifolia, brass buttons, is a widespread fleshy perennial with bright yellow flowers (Allan 1961).
Characters (Black & Robertson 1965): Small herbs with alternate leaves; heads small, with all flowers of equal length, solitary on rather long terminal peduncles. Involucre hemispherical, bracts nearly equal with scarious margins, in about two rows; receptacle naked; outer flowers female or bisexual, fertile, usually without corollas; disk-flowers numerous, tubular, four-toothed, bisexual and sterile or fertile; achenes very small (rarely over one millimetre long), more or less compressed, smooth or almost so; pappus absent.
<==Cotula Linnaeus 1753A61
|--C. (subg. Cotula) coronopifolia Linnaeus 1753A61 (see below for synonymy)
|--C. anthemoides [incl. Nananthea tassiliensis Batt. & Trab. 1913]D17
|--C. (subg. Strongylosperma) australis (Sieb. ex Spreng.) Hooker 1853 (see below for synonymy)A61
|--C. bipinnataBR65
|--C. cinerea [=Brocchia cinerea]D17
|--C. cotuloidesGK00
|--C. filifoliaBR65
|--C. hemisphaericaVB02
| -C. monticola Simpson 1952 (n. d.)A61
|--C. reptansBR65
|--C. scariosaD03
|--C. turbinataGK00
`--C. vulgaris Levyns 1941 [incl. C. filifolia var. decumbens]BR65
Cotula australis (Sieb. ex Spreng.) Hooker 1853 [=Anacyclus australis Sieb. ex Spreng. 1826, Strongylosperma australe Less. 1832; incl. Cotula venosa Colenso 1891]A61
Cotula coronopifolia Linnaeus 1753A61 [incl. C. integrifolia Hooker 1856A61, C. coronopifolia var. integrifoliaC06]
*Type species of generic name indicated
References
[A61] Allan, H. H. 1961. Flora of New Zealand vol. 1. Indigenous Tracheophyta: Psilopsida, Lycopsida, Filicopsida, Gymnospermae, Dicotyledones. R. E. Owen, Government Printer: Wellington (New Zealand).
[BR65] Black, J. M., & E. L. Robertson. 1965. Flora of South Australia. Part IV. Oleaceae–Compositae. W. L. Hawes, Government Printer: Adelaide.
[C06] Cheeseman, T. F. 1906. Manual of the New Zealand Flora. John Mackay, Government Printer: Wellington.
[D17] Diels, L. 1917. Beiträge zur Flora der Zentral-Sahara und ihrer Pflanzengeographie. Nach der Sammelausbeute des Freiherrn Hans Geyr von Schweppenburg. Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie 54 (Beiblatt 120): 51–155.
[D03] Dusén, P. 1903. The vegetation of western Patagonia. In: Scott, W. B. (ed.) Reports of the Princeton University Expeditions to Patagonia, 1896–1899 vol. 8. Botany pp. 1–34. The University: Princeton (New Jersey).
[GK00] Gibson, N., & G. J. Keighery. 2000. Flora and vegetation of the Byenup-Muir reserve system, south-west Western Australia. CALMScience 3 (3): 323–402.
[VB02] Vijay, S. K., & T. N. Bhardwaja. 2002. Vegetation and phenodynamics of wetlands of central Rajasthan. Journal of the Bombay Natural History Society 99 (3): 573–581.