Newtonia Baill., Bull. Mens. Soc. Linn. Paris 1(91): 721. 1888.

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

Newtonia Baill., Bull. Mens. Soc. Linn. Paris 1(91): 721. 1888.

Figs 127 , 131

Type.

Newtonia insignis Baill. [= N. duparquetiana (Baill.) Keay]

Description.

Unarmed large trees, often with buttresses (Fig. 127D ) and aerial roots (one species a liana), tuberous storage roots absent; brachyblasts absent. Stipules small, caducous. Leaves bipinnate, extrafloral nectaries present between the proximal pair of pinnae and usually between all pairs, sessile or stipitate, crateriform to cylindrical; pinnae 1-27 pairs, opposite; leaflets 1-40 (67) pairs per pinna, opposite, sessile, pinnately veined, brochidodromous. Inflorescences paniculiform comprising aggregated spikes (Fig. 127H ) (a raceme in one species), terminal or subterminal. Flowers sessile or pedicellate, functionally staminate or bisexual; hypanthium absent but the stamens and petals fused into a stemonozone, forming a nectary disk in several species; calyx 5 lobed, valvate; petals 5, valvate, basally connate or adnate to stamens; stamens 10, free above the stemonozone, anthers dorsifixed, anther glands present or absent; pollen in tricolporate monads, exine smooth (perforated), columellae present; ovary stipitate, stigma porate. Fruits strongly dorsiventrally flattened, dehiscing along ventral suture (Fig. 127N ), valves coriaceous, exocarp brown, reticulately veined, endocarp lighter in colour, mesocarp absent. Seeds strongly flattened, winged (Fig. 127N ), longitudinal, the testa thin, pleurogram absent, funicle attached apically.

Chromosome number.

2 n = 26 ( Goldblatt 1981b).

Included species and geographic distribution.

Eleven species, restricted to, but widely distributed in tropical Africa (Fig. 131 ).

Ecology.

Newtonia species are (with the exception of N. scandens Villiers) large trees, often with buttresses (Fig. 127D ) and aerial roots, mostly in rainforests, although some species are found in more seasonal semi-deciduous forest in East Africa (Fig. 131 ). Seeds wind-dispersed (Fig. 127N ).

Etymology.

Named by Baillon in honour of the English philosopher and mathematician Isaac Newton.

Human uses.

Various species are used for timber ( Fern 2023).

Notes.

Newtonia is one of three genera of large, unarmed African trees with winged seeds that form part of the grade subtending the core mimosoid clade (Fig. 126 ). The follicular dehiscence of fruits of Newtonia , i.e., along one margin only, to release the winged, wind-dispersed seeds (Fig. 127N ), is unusual in Mimoseae and found in only a few other genera (e.g., Cylicodiscus , Piptadeniastrum Brenan, Pityrocarpa (Benth.) Britton & Rose, and Marlimorimia L.P. Queiroz, L.M. Borges, Marc.F. Simon & P.G. Ribeiro). The spicate inflorescences are always aggregated into compound paniculiform terminal inflorescences (Fig. 127H ).

In the past, several New World species were included in Newtonia . These are now placed in the genus Marlimorimia , a genus of the Stryphnodendron clade segregated from Pseudopiptadenia Rauschert by Borges et al. (2022), reflecting long-documented differences in pollen type [tricolporate monads in Newtonia vs polyads in Pseudopiptadenia (now Marlimorimia ; Guinet 1969)] and other morphological differences ( Lewis and Elias 1981; Lewis and Lima 1991).

Taxonomic references.

Brenan (1959); Hutchinson and Dalziel (1958); Mackinder and Cheek (2003); Villiers (1989, 1990), all with illustrations.

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