The Guadalupian series and the Permian timescale
— Spencer G. Lucas

The Permian System was divided into two series, lower and upper, for more than a century, but in the 1990s a third middle series was added to reflect better the physical and biological events of Permian Earth history. The three Permian series also received formal names (ascending: Cisuralian, Guadalupian, and Lopingian). The Guadalupian Series consists of three stages (ascending: Roadian, Wordian, and Capitanian) that have Global Stratotype Sections and Points (GSSPs) that define their bases in the Guadalupe Mountains of west Texas. Beginning in 2013, a new effort began to restudy the Guadalupian GSSPs, and it has revealed problems with all three Guadalupian stage-base GSSPs. Clearly, there is a need to redefine the GSSPs of at least the base of the Roadian and Wordian. The problems with the Guadalupian GSSPs reveal the politics of the International Commission on Stratigraphy (which led to premature and unsubstantiated original definitions during the 1990s) and the relative lack of understanding and agreement on stratigraphic ranges and the taxonomy of the conodonts used as primary signals to define the GSSPs. Clearly, more work is needed and expected to redefine and refine Guadalupian chronostratigraphy as a part of the Permian timescale.