Pterygota Notes

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Synonymy of Pterygota

Introduction

Pterygota is a genus of malvaceous trees, placed in subfamily Sterculioideae/tribe Sterculieae, with a pan-tropical, rain-forest, distribution. The genus was introduced in 1832 [a]. The number of species is not clear - Kubitzki and Bayer [1] write "probably more than 10 species". The Flora of Madagascar [2] gives a count of 17 species, including two from Borneo, and two from New Guinea. The Flora of China [3] says "about 20 species". There are 4 species in the Neotropics. The African Flowering Plant Database (AFPD) [4] recognises 8 species in Africa, with an additional name (Pterygota kamerunensis K.Schum. & Engl.) of uncertain status, but only 3 of these are at all well known. However the Flora of Tropical East Africa [5] rejects one of these. The flora of Madagascar [2] includes 2 species. The type species, Pterygota alata, is found in south, southeast and east Asia, There is one species from Ceylon. In addition to Pterygota alata there are 5 species from Malesia and Papua. Putting these together produces a count of 21 species, which I present as a tentative enumeration of the species of the genus.

Like the other genera of Sterculioideae species of Pterygota have alternate, petiolate, foliage and possess apetalous (lacking petals), exinvolucellate (lacking an epicalyx) flowers with a fleshy, usually petaloid, gamosepalous (fused) calyx, an absence of staminodes, a monadelphous staminal column, an androgynophore (a stalk separating the calyx from the stamens and styles), and apocarpous (i.e. separated) ovaries and fruits. The key character distinguishing Pterygota from the other genera of the subfamily is the possession of winged seeds. Other traits common in Pterygota are large, broadly ovate to suborbicular, long-petiolate. unlobed, entire-margined, palmately-nerved leaves clustered at the end of branches, pluriovulate ovaries with biserriate axile placentation, and large, many-seeded, ventrally dehiscent, flattened subovoid, stipitate, follicles. The calyx and gynoecium are usually pentamerous. There are exceptions - for example Pterygota horsfieldii has 4- (less commonly 3-)merous calyces and gynoecia, and Pterygota colombiana has narrow, palmatipinnate, leaves.

Neotropical Species

Four species of Pterygota are found in the Americas, where the genus is found in Costa Rica, in northern Colombia and Venezuela, in eastern Brasil, and in Peruvian and Bolivian Amazonia. A single record, not identified to species, is known from Guatemala. Two of these species, P. brasiliensis and P. excelsa, were previously placed in Basiloxylon, which has subsequently been reduced to Pterygota [6].

The American species generally have narrower leaves with less obtuse apices that the Old World species. While the leaves of P. amazonica and P. brasiliensis are 5-nerved at the base, the outermost pair of veins is less prominent that the other 3, and those of P. colombiana are 3-nerved at the base (palmatipinnate).

Pterygota amazonica L.O.Williams