Anonychium (Benth.) Schweinf., Reliq. Kotschy.: 7. 1868.

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

Anonychium (Benth.) Schweinf., Reliq. Kotschy.: 7. 1868.

Figs 127 , 128

Prosopis sect. Anonychium Benth., J. Bot. (Hooker) 4: 347. 1841. Type: Prosopis oblonga Benth. [= Anonychium africanum (Guill. & Perr.) C.E. Hughes & G.P. Lewis]

Type.

Anonychium lanceolatum (Benth.) Schweinf. [≡ Prosopis lanceolata Benth. (= Anonychium africanum (Guill. & Perr.) C.E. Hughes & G.P. Lewis)]

Description.

Unarmed trees 4-20 m high (Fig. 127A ), brachyblasts absent. Stipules inconspicuous, caducous as young leaves develop. Leaves somewhat pendulous, bipinnate; fleshy, cup or tub-shaped, porate extrafloral nectaries between most pinnae pairs and similar, but smaller, nectaries often between some or most leaflet pairs; pinnae 1-4 pairs; leaflets 4-13 pairs per pinna, opposite, mid-vein sub-centric. Inflorescences spiciform racemes, solitary or in pairs in axils of coevally developing leaves, densely flowered (Fig. 127E ); pedicels 0.5 mm. Flowers small, yellowish or greenish-white, sweetly scented; calyx gamosepalous, ca. 1 mm long; petals 5, free, glabrous; stamens 10, anthers apically broadened with an anther gland borne ventrally between the thecae forming a triangular hood-shaped protrusion made up of papillate cells; pollen in tricolporate monads with costae on the pores and a smooth (perforated) exine with columellae; ovary sessile. Fruits indehiscent, straight or sub-falcate, dark reddish-brown to blackish, shiny, subterete in cross-section (Fig. 127I ), exocarp hard, 1-2 mm thick, mesocarp spongy, thick, dry, endocarp segmented, segments enclosing the seeds, thin, transverse (at right angles to fruit length), in one row, seeds many. Seeds dark brown to black, compressed, rattling within the pod when ripe, pleurogram present 75%, testa hard.

Chromosome number.

2 n = 28 ( Bukhari 1997).

Included species and geographic distribution.

Monospecific ( A. africanum ), widespread across Sahelian Africa, from Senegal in the west to Sudan in the east (Fig. 128 ).

Ecology.

Native across the whole Sahelian savanna belt. Seeds dispersed by herbivores.

Etymology.

Anonychium from the Latin or Greek onych = ónyx (= nail or claw), meaning the absence of nails or claws, in reference to the lack of armature of this genus.

Human uses.

Trees of Anonychium are maintained and managed by farming and pastoralist communities in traditional silvo-pastoral and agroforestry systems throughout the African Sahel (Figs 127A , 128 ), providing essential products, including wood, fuel, food, livestock fodder and medicines and enhancing soil fertility ( Leakey and Last 1980). The highly nutritious indehiscent fruits are eagerly consumed by large herbivores including all forms of livestock, such as camels, cattle and goats at the end of the dry season and harvested by farmers to feed to their animals; cow dung (containing viable seeds) is used to fertilise fields.

Notes.

The genus Anonychium was resurrected by Hughes et al. (2022b), along with the genera Strombocarpa Engelm. & A. Gray and Neltuma Raf., to account for the non-monophyly of the genus Prosopis L. Prior to that, Prosopis africana (Guill. & Perr.) Taub. had long been considered anomalous within Prosopis , having been previously placed in its own genus, Anonychium by Schweinfurth (1868) under the name Anonychium lanceolatum Schweinf. and, later, its own section Prosopis Anonychium of Prosopis ( Bentham 1841b; Burkart 1976). Unlike Prosopis and its other segregate genera Strombocarpa and Neltuma , Anonychium lacks armature, has internally glabrous petals, pollen with costae, V-shaped anthers with small stomia forming short pockets on the ventral surface of the anthers and unusual sessile anther glands borne ventrally between the thecae, rather than stipitate glands borne apically or dorsally from the connective between the thecae as in most other Mimoseae , and forming triangular hood-shaped protrusions made up of papillate cells which are also unique amongst mimosoid anther glands ( Luckow and Grimes 1997). This distinctive combination of morphological features separating Anonychium from Prosopis is reflected in the phylogenetic placement of Anonychium as an isolated lineage subtending the grade of other unarmed genera, Plathymenia , Fillaeopsis and Newtonia , which together are paraphyletic with respect to the core mimosoid clade (Fig. 126 ; Ringelberg et al. 2022).

Taxonomic references.

Bentham (1841b); Brenan (1959), with illustration; Burkart (1976); Hughes et al. (2022b); Luckow and Grimes (1997).

Figures

Figure 126. Phylogenetic relationships across the grade Newtonia of four genera subtending the core mimosoid clade in tribe Mimoseae. For description of phylogeny and support values, see Fig. 6 caption (page 63).

Figure 127. Habit, habitats, inflorescences, and fruits of Newtonia and allies A small tree of Anonychium africanum (Guill. & Perr.) C. E. Hughes & G. P. Lewis in Senegal, West Africa B small twisted treelet of Plathymenia reticulata Benth. in savanna grasslands (Cerrado) in eastern Bolivia C large, buttressed tree base of Fillaeopsis discophora Harms in tropical wet forest, Ebo, Cameroon D large buttressed tree base of Newtonia buchananii (Baker f.) G. C. C. Gilbert & Boutique in semi-evergreen forest in Mozambique E spicate inflorescence of Anonychium africanum F spicate inflorescences of Plathymenia reticulata, eastern Bolivia G spicate inflorescences of Fillaeopsis discophora, Gabon H spicate inflorescences of Newtonia buchananii in Malawi I indehiscent pods of Anonychium africanum collected as livestock feed in Burkina Faso, West Africa J tardily dehiscent pods with chartaceous or weakly coriaceous valves of Plathymenia reticulata, eastern Bolivia K pod valves and papery endocarp packets surrounding seeds of Plathymenia reticulata, Bahia, Brazil L tardily dehiscent pods with chartaceous valves of Fillaeopsis discophora in tropical wet forest in Mayombe, Congo (Brazzaville) M large winged seeds of Fillaeopsis discophora in tropical wet forest in Ambam, Cameroon N fruits and winged seeds of Newtonia buchananii in cultivation in South Africa. Photo credits A S Christensen www. westafricanplants. senckenberg. de B, F, J, K, N CE Hughes C, L, M X van der Burgt D Stefaan Dondeyne E M Arbonnier https: // agritrop. cirad. fr / G E Bidault, Missouri Botanical Garden, http: // legacy. tropicos. org / Image / 100618759 H G Baumann www. westafricanplants. senckenberg. de I M Schmidt www. westafricanplants. senckenberg. de.

Figure 128. Distribution of Anonychium based on quality-controlled digitised herbarium records. See Suppl. material 1 for the source of occurrence data.