Abstract
The establishment of native species-dominated forest parks and investment into vegetation surveys and taxonomic research has not only enabled the discovery of relictnative species affected by urban expansion but also facilitated targeted conservation efforts. During investigations on plant diversity and vegetation status in Longquan Mountain Urban Forest Park in eastern Chengdu Metropolis, West China, an unidentified species of Euonymus (Celastraceae) was encountered. It resembles both E. chloranthoides and E. aquifolium in vegetative appearance, but it has exclusively 4-merous flowers. A phylogenetic analysis incorporating 51 taxa of Euonymus and Glyptopetalum supported its recognition as a new species, positioned phylogenetically sister to a clade containing Glyptopetalum species, and close to E. chloranthoides and E. aquifolium. To acknowledge the expanded Chengdu urbanization and the recently planned mountain urban forest park, it is described as E. chengduanus, and its diagnostic morphological characters are compared with E. aquifolium, E. chloranthoides, and Glyptopetalum ilicifolium. This discovery implies that even in intensively anthropogenic-impacted areas adjacent to large cities, undocumented plant diversity may still exist. Consequently, this new species is tentatively assessed as Critically Endangered (CR) to emphasize both the urgency of its protection and to raise public awareness concerning biodiversity in degraded ecosystems.