Clarkina, which characterizes Upper Permian (Lopingian Series) strata, evolved from Jinogondolella altudaensis in the Delaware basin of West Texas as demonstrated by transitional continuity. The West Texas section is significantly more complete in the uppermost Guadalupian interval than that of the probable GSSP reference section in South China, and clarifies the phylogenetic relationships among other conodont taxa as well. Jinogondolella granti clearly evolved into J. artafrons new species, both characterized by Pa elements with a distinctive fused carina. Representatives of Jinogondolella crofti are limited to the uppermost part of the altudaensis zone, and are interpreted as terminal paedomorphs. The associated foraminifer (non-fusulinid) fauna has some species in common with Zechstein faunas, possibly presaging the evaporitic basin that would develop following this latest Guadalupian marine deposition in West Texas.