水社擬茀蕨過去在臺灣被視為已經滅絕，但是最近我們在屏東縣牡?鄉以及臺東縣?嶼鄉重新發現?此一物種。該種目前均發現於鄰近農耕地旁的溼地，相信極容?受到人為的干擾而再次滅絕。我們依循IUCN 受威脅等級及準則，評估水社擬茀蕨在臺灣的稀有等級為嚴重瀕?滅絕。

The fern, Phymatosorus longissimus (Bl.) Pic. Serm., was believed to be locally extinct in Taiwan. However, we recently rediscovered this species in Mudan, Pingtung County and Lanyu Island, Taitung County of Taiwan. The species has currently been found in wetlands neighboring cultivated fields. These habitats are prone to the disturbance of human activities, which may lead to another future extinction of the species in Taiwan. Based on the IUCN criteria, we proposed Phymatosorus longissimus (Bl.) Pic. Serm. to be a critically endangered species in Taiwan. We also discussed the taxonomy and the distribution of this species.