Neotropical Ixonanthaceae

Paul J.M. Maas & Hiltje Maas-van de Kamer

National Herbarium of the Netherlands (Wageningen branch), Wageningen, the Netherlands.


Trees or shrubsLeaves alternate, simple, margins entire, toothed or crenulate; stipules small or lacking.  Inflorescences axillary or terminal racemes or panicles.  Flowers generally bisexual, actinomorphic, small; sepals 5, imbricate, free or slightly connate at the base; petals 5, imbricate or contorted, free, often reflexed, persistent in fruit; disc present, intrastaminal; stamens 5-20, anthers dithecal, longitudinally dehiscent, introrse; ovary superior, 2-5-locular, style 1, stigma capitate, placentation axile-apical, ovules 1-2 per loculeFruits septicidal or loculicidal, elongate capsules.  Seeds 2-9, basally winged or arillate.

Notes on delimitation

  • In the past the Ixonanthaceae were placed in the Linaceae and Cyrillaceae by most authors, but all recent research support its placement in the order Malpighiales (Stevens, 2008; APG III, 2009).
  • Cronquist (1981) and Takhtajan (2009) both placed the family in the order Linales.

Distribution in the Neotropics

Pantropically distributed, with five genera and a total of ca. 30 species. In the Neotropics two genera comprising nine species occur in the Guayanan Highlands, Guyana, French Guiana, Amazonian Brazil and Bolivia, at elevations of 0-1,400 m.

  • Cyrillopsis Kuhlm. (2 spp.).
  • Ochthocosmus Benth. (7 spp.).

Distinguishing characters (always present)

Key differences from similar families

Differences from Linaceae:
1. Style 1; seeds winged or arillate; fruit a capsule   .... Ixonanthaceae
1. Styles 3-5; seeds without wings or aril; fruit a drupe or capsule …. Linaceae

Useful tips for generic identification

Key to genera of Neotropical Ixonanthaceae

1. Ovary 2-locular, fruit a 2-valved capsule; seeds arillate …. Cyrillopsis
1. Ovary 5-locular, fruit a 5-valved capsule; seeds basally winged …. Ochthocosmus


  • The two genera are native in the Neotropics.
  • Neither genus is cultivated.

General notes

  • Pollinated by bees and flies.
  • Dispersal endozoochorous (by birds) or hydrochorous.

Important literature

A.P.G. III. 2009. An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III. Bot. J. Linnean Soc. 161: 105-121.

Cronquist, A. 1981. An integrated system of classification of flowering plants. Columbia University Press, New York.

Maas, P.J.M. & Westra, L.Y.Th. 2005. Neotropical Plant Families. A concise guide of vascular plants in the Neotropics. 3rd ed., p. 176. A.R.G. Gantner Verlag K.G., Ruggell.

Ramírez, N. & Berry, P.E. 1999. Ixonanthaceae. In  Berry, P.E., Yatskievych, K. and Holst, B. (eds.). Flora of the Venezuelan Guayana vol. 5, pp 664-671. Missouri Botanical Garden Press.

Ramírez, N. 2004. Ixonanthaceae. In: Smith, N.P., Mori, S.A., Henderson, A., Stevenson, D.W., and Heald, S.V. (eds.). Flowering plants of the Neotropics, pp. 195-196. Princeton University Press, Oxford and Princeton.

Stevens, P.F. 2008. Angiosperm Phylogeny Website. Version 9 onwards.

Steyermark, J.A. & Luteyn, J.L. 1980. Revision of the genus Ochthocosmus. Brittonia 32: 128-143.

Takhtajan, A. 1997. Flowering Plants. Second edition. Springer Verlag Berlin.

How to cite

Maas, P.J.M. & Maas-van de Kamer, H. (2012). Neotropical Ixonanthaceae. In: Milliken, W., Klitgĺrd, B. & Baracat, A. (2009 onwards), Neotropikey - Interactive key and information resources for flowering plants of the Neotropics.