Classification of Mesembryanthemaceae

Mesembs are currently classified in Aizoaceae Rudolfi sensu stricto, excluding Molluginaceae (Bittrich & Hartmann 1988; Hartmann 1993). This concept of Aizoaceae comprises five subfamilies: Mesembryanthemoideae Ihlenf., Schwantes & Straka, Ruschioideae Schwantes in Ihlenf., Schwantes & Straka emend. Bittrich & H.E.K.Hartmann, Aizooideae, Sesuvioideae Lindl. and Tetragonioideae Lindl. The monophyly of the first two subfamilies, at times referred to as "Mesembryanthema", is supported by the following synapomorphies: semi-epigynous or epigynous flowers, petals of staminodial origin, raphide crystals of calcium oxalate, and n = 9. The Aizoaceae sensu stricto, excluding Mesembryanthemaceae, is supported by: perianth petaloid on inside, sepaloid on outside, druse crystals of calcium oxalate, and n = 8. The entire Aizoaceae rests on one apomorphy: the evolution of epidermal bladder cell idioblasts. The development of simple hygrochastic or hygroscopic capsules with septal expanding tissue has been suggested as another possible synapomorphy for the Aizoaceae sensu stricto
Recent investigation of evolutionary relationships within Aizoaceae sensu lato (Wallace 1998), using comparative plastid DNA sequencing (rpl16 intron), showed the mesembs to be monophyletic and derived relative to the other groups. The clade represented by Sesuvium was found to be basal in the family with Tetragonia and Aizoon as sister to one another
The outmoded family name Mesembryanthemaceae Fenzl is legitimate: the mesembs were given family status by Herre & Volk: 38 (1948). It is a convenient concept and its continued usage is supported by the sheer size of the group (± 123 genera (incl. Sarcozona), ± 1 680 species), its monophyly, distinctive traits, and distribution - being almost entirely endemic to southern Africa

SUPRAGENERIC CLASSIFICATION

The classification of the Mesembryanthemaceae formulated by Schwantes, subsequently revised and completed by Straka and Ihlenfeldt (Herre 1971), represents the last formally published classification of the mesembs. Bittrich (1986); Gerbaulet: 385 (1995), : 41 (1996a), : 25 (1996b), : 9 (1996c), : 145 (1997) and Klak & Linder: 301 (1998) have done extensive work on the Mesembryanthemoideae, yet at this stage no revised tribal or subtribal classification is available for this group. Changes in rank and clarification of generic boundaries have been the focus of several of these studies
In the Ruschioideae, a number of monophyletic groups are recognised, yet relationships among genera as well as delimitation of genera are still under study and a formal suprageneric classification is not available for this large group which contains approximately 1598 species. Hartmann (: 313 (1988a); : 75 (1991a); 1993; : 32 (1998a) has proposed a provisional system for grouping ruschioid genera, drawing on extensive studies of fruit and flower morphology, epidermal characters, growth form, and seed. The system outlined below is based on these works

Subfamily Mesembryanthemoideae: Genera classified in the subfamily Mesembryanthemoideae share the following characters: stamens and petals (mostly) forming a tube; nectaries koilomorphic (shell-shaped); cortical bundles present; expanding tissue present as expanding keels extending from centre of capsule to tips of valves.
Subfamily Ruschioideae: In the Ruschioideae synapomorphies include: stamens hairy at base; nectaries lophomorphic (crest-shaped); placentation basal or parietal; expanding keels ± restricted to valves; covering membranes often present. The Ruschioideae may be subdivided into the following groups (a question mark indicates uncertain classification):
- 1. Apatesia Group: Plants annual to perennial. Leaves mostly flat, only some bladder cells along the leaf margins. Flowers with a flat, broad nectariferous ring. Capsules with expanding tissue reduced or absent, sometimes breaking into mericarps, often with seed pockets derived from false septa, rarely nuts.
  - Apatesia
  - Carpanthea
  - Caryotophora
  - Conicosia
  - Hymenogyne
  - Saphesia
  - Skiatophytum.
- 2. Cleretum Group: Plants annual. Leaves flat, with prominent bladder cells. Flowers with a flat, broad nectariferous ring. Capsules with or without covering membranes, with or without spongy sills (as closing bodies) at the outer rim of the distal opening, expanding sheets predominant, their extension related directly to the size of the covering membranes.
  - Aethephyllum
  - Cleretum
  - Dorotheanthus.
- 3. Mitrophyllum Group: Plants perennial, heterophyllous, rarely homophyllous, with two leaf pairs per season, sometimes anisophyllous, with prominent bladder cells. Flowers with a lophomorphic nectary ring, rarely reduced. Capsules with complete or reduced covering membranes of constant shape, expanding sheets merging into expanding keels, rarely separate, with or without spongy closing sills or bodies, with broad rectangular valve wings.
  - Dicrocaulon
  - Diplosoma
  - ?Disphyma
  - ?Glottiphyllum
  - ?Hammeria
  - Jacobsenia
  - Meyerophytum
  - Mitrophyllum
  - Monilaria
  - Oophytum.
- 4. Delosperma Group: Plants perennial. Leaves terete to trigonous, rarely flat, with ± prominent bladder cells and/or hairs. Flowers with 5 separate lophomorphic nectaries, with filamentous staminodes, rarely without. Capsules with or without covering membranes, expanding keels and sheets separated, rarely merging, closing bodies absent, valve wings present, broad, rectangular, often with basal seed pockets.
  - Corpuscularia
  - Delosperma
  - Drosanthemum
  - Ectotropis
  - Gibbaeum
  - Lampranthus p.p.
  - ?Malephora
  - Mestoklema
  - Muiria
  - Oscularia
  - Trichodiadema.
- 5. Stomatium Group: Plants perennial, rhizomatous with enlarged rootstocks. Leaf pairs 2 or 3 to a branch, leaves homocellular, xeromorphic, crystals in irregular zones, surface rough or warty from elevations above subhypodermal tannin idioblasts, often denticulate. Flowers with five separate nectaries. Capsules with or without covering membranes, without closing bodies, valve wings broad to reduced.
  - Chasmatophyllum
  - Faucaria
  - ?Frithia
  - ?Mossia
  - Neohenricia
  - Orthopterum
  - Rabiea
  - Rhinephyllum
  - Stomatium.
- 6. Titanopsis Group: Plants perennial, with fleshy tap roots, rarely with fibrous roots, but often with fleshy rhizomes. Leaves in rosettes or only one pair per branch, surface homocellular, xeromorphic, crystal layer in certain areas often predominant, smooth or warty. Flowers solitary, with a lophomorphic nectary ring. Capsules without or with covering membranes, these bending later into the empty locules along a preformed line, with broad valve wings tapering towards the tip of the valve, without or with very small closing bodies.
  - Aloinopsis
  - Deilanthe
  - Didymaotus
  - Dinteranthus
  - Ihlenfeldtia
  - Lapidaria
  - Lithops
  - Nananthus
  - Schwantesia
  - Tanquana
  - Titanopsis
  - Vanheerdea
  - Zeuktophyllum.
- 7. Dracophilus Group: Plants perennial. Leaves heterocellular, xeromorphic, surface rarely sticky. Flowers mostly solitary, with a lophomorphic nectary ring, rarely five separate glands; without, rarely with filamentous staminodes. Capsules mostly 5-locular, with or without covering membranes, without closing bodies, with broad valve wings.
  - Conophytum
  - Dracophilus
  - Hartmanthus
  - Jensenobotrya
  - Juttadinteria
  - Namibia
  - Nelia
  - Psammophora
  - Ruschianthus.
- 8. Bergeranthus Group: Plants perennial. Leaves homocellular, xeromorphic, mostly free to the base. Flowers mostly in exserted inflorescences, with five separate nectaries. Capsules with firm, straight, complete covering membranes, closing bodies present or absent, valve wings reduced.
  - Bergeranthus
  - Bijlia
  - Carruanthus
  - Cerochlamys
  - Hereroa
  - Machairophyllum
  - Rhombophyllum.
- 9. Lampranthus Group: Plants perennial. Leaves free, homocellular, mesomorphic to xeromorphic, crystal layer thin to absent. Flowers with five separate nectaries, sometimes united into a ring. Capsules deep, with firm, complete covering membranes with additional closing devices at their distal recurved ends, opening blocked by sterile funicles, fruit rarely a berry.
  - Antegibbaeum
  - Braunsia
  - ?Carpobrotus
  - Circandra
  - Enarganthe
  - Erepsia
  - Esterhuysenia
  - Lampranthus s.s.
  - Namaquanthus
  - Scopelogena
  - Smicrostigma
  - Vlokia
  - Wooleya.
- 10. Ruschia Group: Plants perennial. Leaves free to connate, surfaces homocellular, xeromorphic, crystal layer thick. Flowers with filamentous staminodes and a lophomorphic nectary ring. Capsules with firm, complete, ± convex covering membranes with closing rodlets at their distal recurved ends, with closing bodies up to medium size, valve wings usually absent; fruit rarely nutlets.
  - Acrodon
  - Arenifera
  - Astridia
  - Ebracteola
  - Khadia
  - Marlothistella
  - Polymita
  - Ruschia s.s.
  - Stayneria.
- 11. Leipoldtia Group: Plants perennial. Leaves free to connate, homocellular, xeromorphic, crystal layer of fine granules, often like sand. Flowers with or without filamentous staminodes, with a lophomorphic nectary ring. Capsules with firm, resilient, ± concave covering membranes with closing ledges, bulges or rodlets at the ± prominent distal recurved ends, closing bodies large, rarely small, rarely absent.
  - Antimima
  - Argyroderma
  - Cephalophyllum
  - Cheiridopsis
  - Cylindrophyllum
  - Fenestraria
  - Hallianthus
  - Jordaaniella
  - Leipoldtia
  - Octopoma
  - Odontophorus
  - Ottosonderia
  - Pleiospilos
  - Schlechteranthus
  - Vanzijlia.
- 12. Eberlanzia Group: Stems whitish. Capsules with valve wings and closing bodies which are mostly small and often deep inside the locules so that they appear absent.
  - Amphibolia
  - Eberlanzia
  - Ruschianthemum
  - Stoeberia

Genera of uncertain classification: Although the following genera have been assigned to groups, these placings are to some extent tentative:

Calamophyllum was left out of the classification and the keys because it is insufficiently known

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