Description from Flora of China
Acer yui var. leptocarpum W. P. Fang & Y. T. Wu.
Trees ca. 7 m tall. Bark brownish gray or blackish gray. Branchlets slender, glabrous; lenticels ovate or nearly rounded, small; winter buds terminal or axillary, ellipsoid, small, scales numerous, exterior ones glabrous, ciliate along margin, interior ones pubescent. Leaves deciduous; petiole purplish or purplish green, 3-4 cm; leaf blade broadly ovate, 3-7 × 2-2.5 cm, papery, abaxially yellow pubescent at vein axils, adaxially glabrous and smooth, primary veins 3, reticulate veins conspicuous abaxially, base nearly rounded or broadly obtuse, 3-lobed or 3-dentate, sinuses 1/3-3/5 width of blade; lobes entire or slightly undulate; middle lobe ovate-triangular or lanceolate, apex acute; lateral lobes triangular-ovate, apex obtuse. Inflorescence corymbose. Infructescence 5-7 cm. Fruiting pedicel 3-5 mm, slender. Fruit 3-5; nutlets convex, ca. 7 × 5 mm, slightly puberulent, veined; wing including nutlet obovate, ca. 2.2 × 1 cm, apex obtuse, wings spreading obtusely. Fl. unknown, fr. Sep.
● Mixed forests, valleys; 1800-2000 m. S Gansu, NW Sichuan.