Cladanthus, as currently understood (see below), is a small genus of five species, all native in the Mediterranean region and southwestern Europe. It is obviously closely related to Anthemis and Chamaemelum and most species were formerly included in the latter genera. However, a molecular study of Chamaemelum Mill. and related genera (Oberprieler 2002, Oberprieler & al. 2007) demonstrated that Chamaemelum as traditionally circumscribed is paraphyletic. Cladanthus arabicus (L.) Cass., the type of Cladanthus, is nested within Chamaemelum sect. Santolinopsis Benedí. This section comprises, among others, Chamaemelum mixtum, a species that agrees with Cladanthus arabicus in floret and achene morphology (Oberprieler l.c.). No close phylogenetic relationship with Chamaemelum sect. Chamaemelum could be evidenced by molecular studies. Therefore, Chamaemelum mixtum (and some related species) were transferred to Cladanthus (Oberprieler & Vogt 2002).
Oberprieler C. (2002) A phylogenetic analysis of Chamaemelum Miller (Compositae, Anthemideae) and related genera based upon nrDNA ITS and cpDNA trnL/trnF IGS sequence variation. Bot. J. Linn. Soc. 138: 255-273.
Oberprieler C., Himmelreich S. & Vogt R. (2007) A new subtribal classification of the tribe Anthemideae (Compositae). Willdenowia 37: 89-114.
Oberprieler C. & Vogt R. (2002) Cladanthus Cass. In: Greuter W. & Raus Th. (eds.), Med-Checklist Notulae, 21. Willdenowia 32: 195-208.