Chinle Group strata are siliclastic red beds that record fluvial, lacustrine and minor eolian deposition in a Late Triassic basin that extended from West Texas-Oklahoma to eastern Nevada, southeastern Idaho and Wyoming. Megafossil plants have been known from the Chinle Group since 1850, and they have been used to construct a biostratigraphy of three floral zones (ascending order): Eoginkgoites, Dinophyton and Sanmiguelia zones. This biostratigraphy can be evaluated by stratigraphically ordering Chinle plant localities using lithostratigraphic and vertebrate-fossil-based correlations, which are independent of the plant biostratigraphy. This reveals that the three zones are stratigraphically successive, and that the bulk of the Chinle paleoflora (more than 50% of the taxa) is from theDinophyton zone. Eoginkgoites is confined to basal Chinle strata, but co-occurring genera restricted to these strata are rare and/or known from a single locality. The Sanmiguelia zone is represented by scattered localities in the middle-upper Chinle and cannot be characterized except by the presence of Sanmiguelia, which is known from less than 10 localities and endemic to Chinle strata. Correlation of Chinle Group plant zones with Newark Supergroup plant sites is consistent with vertebrate-fossil-based correlations. However, Chinle plants only provide a useful biostratigraphy of upper Carnian strata (Eoginkgoites and Dinophyton zones). The Norian-Rhaetian paleoflora of the upper Chinle (Sanmiguelia zone) needs further collecting and study before it can be of much biostratigraphic utility.

Key words: biostratigraphy, Chinle Group, megafossil plant, Triassic, United States