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| Polystichum oligodontum Y.Nong, R.H.Jiang & C.Xiong, in Nong, Jiang, Xiong, Q.-J. Wei, G.-Y. Wei, Ji, Lai et H.-J. Wei, 2025. 稀齿耳蕨 | DOI: doi.org/10.3897/phytokeys.266.156701 |
Abstract
Polystichum oligodontum (Dryopteridaceae), a new fern species in P. subg. Haplopolystichum from three karst caves in northwest Guangxi, China, is described and illustrated. This species is unique in having pinnae with a shallow or nearly free lobe on the acroscopic base and coarsely toothed distal margins. It resembles P. membranifolium and P. kwangtungense in its reflexed and oblong pinnae with an obtuse or rounded apex, but can be easily distinguished by its remote pinnae bearing a lobe at the acroscopic base. The new species also somewhat resembles P. leveillei in the nearly free basal lobe, but differs by its toothed upper pinna margins. Molecular phylogenetic analysis of 56 Polystichum species, based on the rbcL gene, supports the placement of P. oligodontum within P. sect. Sphaenopolystichum, with P. alcicorne as its closest relative. According to the IUCN Red List Categories and Criteria, the new species is assigned to the Critically Endangered (CR) category.
Key words: Cave ferns, coarse tooth, karst area, serration pattern
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| Polystichum oligodontum (from Bama county). A. Inside view of the cave where the new species was discovered; B. Lower portions of stipes showing scales; C, D. Habits; E. Portions of laminae (adaxially); F. Portions of laminae (abaxially); G. Pinna showing sori; H. Portion of pinna showing indusia. |
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| Polystichum oligodontum (from Fengshan County). A. Inside view of the cave where the new species was discovered; B, C. Habit; D. Portions of laminae (adaxially); E. Scales from stipes base (bottom), pinna base (middle) and pinna surface (top); F. Portions of lamina (abaxially). |
Polystichum oligodontum Y.Nong, R.H.Jiang & C.Xiong, sp. nov.
Diagnosis. Polystichum oligodontum is unique by the pinna acroscopic side with a shallow or nearly free lobe at the base and coarsely toothed along distal margins.
Etymology. The specific epithet is derived from the Latin, oligodontum, meaning “few teeth”, and referring to the number of the teeth on pinna margins.
Chinese name. 稀齿耳蕨 (xī chǐ ěr jué).
You Nong, Ri-Hong Jiang, Chi Xiong, Qiu-Jun Wei, Gui-Yuan Wei, Xing-Yun Ji, Ke-Dao Lai and Hong-Jin Wei. 2025. Polystichum oligodontum (subg. Haplopolystichum, Dryopteridaceae), A New cave fern from Guangxi, China. PhytoKeys. 266: 297-310. DOI: doi.org/10.3897/phytokeys.266.156701 [25 Nov 2025]