Rediscovery and lectotypification of Diplazium velutinum Holttum (Athyriaceae), a rare endemic fern from Peninsular Malaysia

Diplazium velutinum Holttum (Athyriaceae) is a rare endemic fern species originally described in 1937 from Cameron Highlands, Pahang, Peninsular Malaysia. Since its original collection by R. E. Holttum, this species has remained poorly documented, with only a single subsequent record in 1988. During floristic surveys conducted in 2018, this species was rediscovered, representing the first documented collection in more than 30 years.

A detailed morphological description is provided, the spore surface ornamentation is characterized, the molecular phylogenetic placement of the species within Athyriaceae is summarized, and ecological characteristics of its habitat are documented. The species is distinguished from its closest congener, D. tomentosum, by lamina dissection and stipe scale characters. Diplazium velutinum clusters together with D. crenatoserratum and D. tomentosum, consistent with its status as a distinct species.

A lectotype is formally designated here for D. velutinum based on the original syntype S. F. N. 31221 held at the Singapore Botanic Gardens Herbarium (SING). This rediscovery demonstrates the value of continued pteridological surveys in the montane forests of Peninsular Malaysia and highlights the scientific significance of protecting montane forest habitats.