Description from Flora of China
Acer maximowiczii subsp. porphyrophyllum W. P. Fang; A. pectinatum Wallich ex G. Nicholson subsp. maximowiczii (Pax) A. E. Murray; A. urophyllum Maximowicz.
Trees to 12 m tall, andromonoecious. Bark blackish brown, smooth. Branchlets slender, glabrous; winter buds oblong-ellipsoid, glabrous. Leaves deciduous; petiole 5-7 cm, glabrous; leaf blade abaxially pale green, adaxially dark green, ovate or triangular-ovate, 6-11 × 4-9 cm, papery, abaxially rufous pubescent at axils of lateral veins and base of main veins, adaxially glabrous, base subcordate or cordate, rarely truncate, margin doubly serrulate and lobulate with adpressed apiculate coarse teeth, distinctly 5-lobed; middle lobe triangular-ovate or ovate, apex caudate-acuminate; lateral lobes ovate; basal lobes ovate, small. Inflorescence terminal on leafy branchlets, pendulous, racemose, 4-5 cm, 10-15-flowered, appearing after leaves develop fully. Staminate flowers: pedicel 3-4 mm, glabrous; sepals 5, ovate-oblong, apex obtuse; petals 5, obovate; stamens 8; disk intrastaminal; ovary rudimentary. Pistillate flowers: pedicel ca. 6 mm, slender, glabrous; sepals 5, elliptic, apex obtuse; petals 5, ovate-oblong, apex obtuse; stamens 8, disk very short, glabrous, intrastaminal; ovary purple, glabrous; style very short. Fruit brownish yellow; nutlets flat, ca. 6 mm in diam.; wing including nutlet 1.8-2.5 cm × ca. 8 mm, wings spreading obtusely. Fl. May, fr. Sep.
● Mixed forests, valleys; 1800-2500 m. S Gansu, NE Guangxi, Guizhou, W Henan, W Hubei, Hunan, S Qinghai, S Shaanxi, S Shanxi, Sichuan.