Cylicodiscus Harms, Nat. Pflanzenfam. Nachtr. II-IV, 1: 192. 1897.

Bruneau, Anne, de Queiroz, Luciano Paganucci, Ringelberg, Jens J., Borges, Leonardo M., Bortoluzzi, Roseli Lopes da Costa, Brown, Gillian K., Cardoso, Domingos B. O. S., Clark, Ruth P., Conceicao, Adilva de Souza, Cota, Matheus Martins Teixeira, Demeulenaere, Else, de Stefano, Rodrigo Duno, Ebinger, John E., Ferm, Julia, Fonseca-Cortes, Andres, Gagnon, Edeline, Grether, Rosaura, Guerra, Ethiene, Haston, Elspeth, Herendeen, Patrick S., Hernandez, Hector M., Hopkins, Helen C. F., Huamantupa-Chuquimaco, Isau, Hughes, Colin E., Ickert-Bond, Stefanie M., Iganci, Joao, Koenen, Erik J. M., Lewis, Gwilym P., de Lima, Haroldo Cavalcante, de Lima, Alexandre Gibau, Luckow, Melissa, Marazzi, Brigitte, Maslin, Bruce R., Morales, Matias, Morim, Marli Pires, Murphy, Daniel J., O'Donnell, Shawn A., Oliveira, Filipe Gomes, Oliveira, Ana Carla da Silva, Rando, Juliana Gastaldello, Ribeiro, Petala Gomes, Ribeiro, Carolina Lima, Santos, Felipe da Silva, Seigler, David S., da Silva, Guilherme Sousa, Simon, Marcelo F., Soares, Marcos Vinicius Batista & Terra, Vanessa, 2024, Advances in Legume Systematics 14. Classification of Caesalpinioideae. Part 2: Higher-level classification, PhytoKeys 240, pp. 1-552 : 1

Cylicodiscus Harms, Nat. Pflanzenfam. Nachtr. II-IV, 1: 192. 1897.

Figs 132 , 133 , 134

Cyrtoxiphus Harms, Nat. Pflanzenfam. Nachtr. II-IV 1: 203. 1897. Type: Cyrtoxiphus staudtii Harms [= Cylicodiscus gabunensis Harms]

Type.

Cylicodiscus gabunensis Harms

Although Cylicodiscus is clearly a member of the core mimosoid clade, its phylogenetic relationship to the Prosopis clade, from which it is separated by a very short branch, and to the Neltuma clade, are not well-resolved (Fig. 132 ). For this reason, Cylicodiscus is here presented as a separate monogeneric lineage rather than being included in another named clade of Mimoseae .

Description.

Very large trees 25-65 m, to 70+ cm trunk diameter, bole straight cylindrical, thick wandering buttresses with knee-like outgrowths (Fig. 133A-C ) and small adventitious roots at base; trunks of young trees armed with sharply tipped pyramidal scattered woody protuberances (Fig. 133D ); bark fibrous, rough, black-brown; slash brownish-yellow or reddish-orange, wood very hard, brachyblasts absent. Stipules caducous. Leaves bipinnate, petiole bearing a round, sunken nectary at the apex; pinnae 1-3 pairs, opposite; leaflets 3-7 pairs per pinna, alternate, venation brochidodromous. Inflorescences of solitary, axillary spiciform racemes; unfertilised flowers abscising post-anthesis to leave peg-like pedicels (Fig. 133E ). Flowers white; hypanthium absent; calyx 5-lobed, valvate; petals 5, valvate, free; stamens 10, free, anthers dorsifixed, bearing an apical globose gland; intra-staminal disk present, well-developed; pollen in tricolporate monads, exine smooth (perforated), columellae present; ovary sessile/stipitate, stigma porate. Fruits pendulous, linear oblong, strap-like, up to 1 m long, dehiscent along the ventral suture (Fig. 133F ), flattened, woody, ca. 10-seeded, exocarp cracking when mature, sutural ribs flattened, 5 mm wide; mesocarp of two layers, a black glassy layer underlying the endocarp and a reticulate, cardboard-like fibrous layer below that; endocarp smooth, fibrous. Seeds ellispoid, large, to 13 cm long and 2 cm wide (Fig. 133I ) surrounded by a thin papery wing 6 mm wide, testa thin, papery, pleurogram absent, the funicle attached to the short end of the seed.

Chromosome number.

Unknown.

Included species and geographic distribution.

Monospecific ( C. gabunensis ), west and central Africa in Cameroon, Côte d’Ivoire, Equatorial Guinea, Gabon, Ghana, and Nigeria, widespread but apparently uncommon (or perhaps just difficult to collect!) (Fig. 134 ).

Ecology.

Very large canopy-emergent trees with massive crowns in well-drained evergreen lowland tropical Guineo-Congolan rainforest (Fig. 133A-C ) and moist semi-deciduous forests. In common with several other genera of Mimoseae such as Fillaeopsis and some species of Entada , the flowers of Cylicodiscus are very small, yet give rise to very large fruits. Seeds winged and likely wind-dispersed (Fig. 133G-I ).

Etymology.

From Greek cylico (= cup-shaped) and Latin discus (= disk), referring to the cup-shaped floral disk to which the stamens are attached.

Human uses.

The timber of C. gabunensis is very dense and used in heavy construction, for railway sleepers and flooring (Ndonda Makemba et al. 2019).

Notes.

Phylogenetically, Cylicodiscus is separated by a very short branch from the Prosopis clade (Fig. 132 ). It is perhaps notable that both genera of the Prosopis clade, Prosopis L. and Indopiptadenia Brenan, share internodal prickles and/or sharp pyramidal scattered woody protuberances on the stem and shoots with Cylicodiscus (Figs 133D , 135B, C, E ). Although the relationship of Cylicodiscus to the Prosopis and Neltuma clades remains uncertain, Cylicodiscus is clearly a member of the core mimosoid clade and shares presence of armature with the other two first-branching lineages of that clade.

Taxonomic references.

Aubréville (1959) with illustration; Burkill (1995); Ndonda Makemba et al. (2019); Villiers (1989) with illustrations.

Figures

Figure 6. Generic relationships in tribe Ceratonieae. Left part of figure shows complete genus-level Caesalpinioideae phylogeny with the Ceratonieae indicated with a red rectangle. Branch lengths are expressed in coalescent units and terminal branches were assigned an arbitrary uniform length for visual clarity. Support for relationships is based on fractions of supporting and conflicting gene trees: pie charts show gene tree support and conflict per node (blue representing supporting gene trees, green gene trees supporting the most common alternative topology, red gene trees supporting further alternative topologies, grey gene trees uninformative for this node), and numbers above pie charts are Internode Certainty All support values [both calculated with PhyParts (Smith et al. 2015)]. If present, red numbers below pie charts are non-significant (i. e.> 0.05) outcomes of ASTRAL's polytomy test (Sayyari and Mirarab 2018), which tests for each node whether the polytomy null model can be rejected. Monophyletic genera are represented by single branches; see Suppl. material 2 for a phylogeny with all accessions. See Suppl. material 3 for gene tree support across the phylogeny. The phylogeny is a pruned version of the backbone phylogeny of Ringelberg et al. (2023), where full details of the data and phylogenomic analysis methods are presented.

Figure 132. Phylogeny showing the relationships among Cylicodiscus and the genera of the Prosopis clade and the Neltuma clade, the first-branching lineages of the core mimosoid clade of tribe Mimoseae. Substantial gene tree conflict is associated with the relationships of Cylicodiscus which is separated from the Prosopis clade by a very short branch (see inset for exact branch lengths printed above branches). For description of phylogeny and support values, see Fig. 6 caption (page 63).

Figure 133. Habit, leaves, flowers and fruits of Cylicodiscus in wet tropical forest in west Africa A, B Cylicodiscus gabunensis Harms, large canopy emergent tree C mature tree trunk with large knee-like buttresses D immature understory sapling showing sharp-pointed woody protuberances on stem E leaves showing leaflets with conspicuous drip tips F inflorescences G strap-like legumes (ca. 1 m long) showing follicular dehiscence H canopy-emergent tree crown with long strap-like pendulous fruits I 12 cm long winged seeds. Photo credits A, B, D, E, G W Hawthorne C X van der Burgt F, H, I R Ndonda Makemba.

Figure 134. Distribution of Cylicodiscus based on quality-controlled digitised herbarium records. See Suppl. material 1 for the source of occurrence data.

Figure 135. Habit, armature, inflorescences, and fruits of genera of the Prosopis clade A Small tree of Indopiptadenia oudhensis (Brandis) Brenan in disturbed seasonal monsoon vegetation in Uttar Pradesh, northern India B, C scattered internodal sharply tipped woody protuberances on trunk and branches of young Indopiptadenia oudhensis trees in Uttar Pradesh, northern India D trees of Prosopis cineraria (L.) Druce lopped for animal fodder on the arid fringes of the Thar desert, Rajasthan, India E internodal prickles on young shoot of Prosopis farcta (Banks & Sol.) J. F. Macbride F inflorescences of Indipiptadenia oudhensis in Uttar Pradesh, northern India G inflorescences of Prosopis farcta H unripe, plano-compressed fruits of Indopiptadenia oudhensis in Uttar Pradesh, northern India I indehiscent fruits with a thickened mesocarp of Prosopis farcta. Photo credits A-C, F, H O Bajpai and L Babu Chaudhary D CE Hughes E Zeynel Cebeci https: // commons. wikimedia. org / wiki / File: Prosopis _ farcta _ - _ Syrian _ mesquite _ 01. JPG G Eitan Ferman https: // de. wikipedia. org / wiki / Prosopis _ farcta # / media / Datei: Prosopis _ farcta, _ flower. jpg I Zeynel Cebeci https: // en. wikipedia. org / wiki / Prosopis _ farcta # / media / File: Prosopis _ farcta _ 01. JPG.