The populations of pitvipers from south western Costa Rica, have traditionally been identified as Bothriechis schlegelii (Berthold). However, in 1954 E. H. Taylor described one specimen from the area as a new subspecies, B. schlegelii supraciliaris. Werman returned supraciliaris to synonymy with schlegelii four decades later. However, morphometry and color pattern in a SW Costa Rica population (25 specimens) differ from those of specimens (N=57) from other parts of Costa Rica and from descriptions of South American specimens. Here the epithet Bothriechis schlegelii supraciliaris Taylor 1954, is reestablished as a valid taxon and elevated to specific rank as B. supraciliaris stat.nov. It is closely related to B. schlegelii from which it differs by its color patterns based on a uniform ground color with polymorphic dorsal designs, and its lower counts of ventral and caudal scales.
