Polyalthia corticosa (Pierre) Finet & Gagnep., newly recorded from Thailand, is described. Two lectotypes are selected here.
Thailand.— NORTHERN: Phrae (Huai Hom, Ban Nam Krai, Huai Yuak), Uttaradit.
Distribution.— Laos, Vietnam.
Ecology.—Along streams in dry evergreen forest, 500–800 m. Flowering Feb.–May, fruiting March–July.
Vernacular.— Sa ban nga pa (สบันงาป่า).
Specimens examined.— A. Chanthamuk 43 (BKF); C. Phengklai 50 (BKF); T. Smitinand & A. Cheke 10805 (BKF).
Notes.— Polyalthia corticosa differs from P. evecta (Pierre) Phamh. (characters in brackets) in being a medium-sized (shrubby tree) tree, with rough (smooth) twigs, with the outer and inner petals more or less the same size (inner petals larger) and with two (one) ovules per carpel The Thai specimens extend the range of P. corticosa from Vietnam and Laos westward to northern Thailand.
Bunchalee P, Chantaranothai P. 2006 Notes on Polyalthia (Annonaceae). Thai Forest Bull., Bot. no. 34. 1-3.: http://web3.dnp.go.th/botany/PDF/TFB/TFB34/TFB34_1Polyalthia.pdf