Lycopodium carinatum Desvaux ex Poiret in Lamarck, Encycl., Suppl. 3: 555. 1814; Huperzia carinata (Desvaux ex Poiret) Trevisan; H. laxa (C. Presl) U. Sen & T. Sen; L. acrostachyum Hooker & Greville; L. carinatum var. minus Tagawa; L. flagellaria Bory; L. laxum C. Presl; L. pendulum Roxburgh; Urostachys carinatus (Desvaux ex Poiret) Herter ex Nessel.

Lycophytes, medium-sized. Stems caespitose, mature branches pendulous, 1 to several times forked, 31-49 cm, branches slightly robust, stem together with leaves cordlike, tertiary branches with leaves more than 2.5 mm in diam., lateral branches unequal. Leaves twisted and forming 2 rows. Trophophylls dense, adnate to branches, much incurved, lustrous, acicular, up to 8 × 4 mm, midrib indistinct, hard, raised abaxially and keeled, base cuneate, decurrent, sessile, margin entire, apex acuminate, substraight, opening outside. Strobili terminal on branches, ca. 3 mm in diam. Sporophylls ovate, midrib indistinct, base cuneate, margin entire, apex acute, with mucro. Sporangia hidden inside of sporophylls, indistinct, yellowish, reniform, vertically bisected.

The trophophylls of Phlegmariurus carinatus are acicular, and its sporangia are hidden inside of its sporophylls; these characters are conspicuously different from other heterophyllous species in the genus.

Epiphytic on tree trunks or rocks in dense forests of ridges, valleys, hills; 200-2300 m. Guangdong, Guangxi, Hainan, Taiwan, Yunnan (Hekou) [Cambodia, India, Japan, Laos, Malaysia, Philippines, Singapore, Thailand, Vietnam; Pacific islands].