A new vascular plant species from Sakhalin, Astragalus sugawarae Kimura-Yokoyama & Shutoh (Fabaceae), based on redescription of an invalid protologue

“ Astragalus calcareus Sugawara” is an invalid name proposed for plant specimens collected from Sakhalin before World War II. Recently, the name was synonymized with A. sachalinensis , a similar species endemic to Sakhalin that belongs to section Oroboidei , but morphological descriptions for these names differ in flower color and hairs on the leaflets. Therefore, we aimed to clarify the taxonomic identity of “ A. calcareus Sugawara”. We searched for herbarium specimens identified by this name and compared their morphology with that of all morphologically similar species. We located four specimens of “ A. calcareus Sugawara”, and their morphology was consistent with the morphological descriptions for the name. No taxa with morphological characters identical to those of the four specimens were examined. The most morphologically similar species, A. austrosachalinensis and A. kurgankolensis , differed from “ A. calcareus Sugawara” in several characters, such as flower color and hairs on the legume, leaflets, calyx, and bracts. We concluded that the specimens of “ A. calcareus Sugawara” should be recognized as a distinct species. Because a homonym has been validly published, we provide a new species epithet, A. sugawarae Kimura-Yokoyama & Shutoh. The phylogenetic relationships and conservation status of the species remain unknown because no recently collected specimens have been traced.