Trilobites occur in two generically distinct faunas in the Permian strata of West Texas. The stratigraphically lower fauna, composed of Ditomopyge decurtata (Gheyselinck), Ditomopyge sp., Triproetus angustus n. sp., Triproetus tumidus n. sp., Triproetus altasulcus n. sp., is present in Wolfcampian and early Leonardian strata. The stratigraphically upper fauna, present in late Leonardian and Guadalupian strata, is comprised of Delaria antiqua (Girty), Delaria granti n. sp., Delaria brevis n. sp., Delaria westexensis n. sp., Delaria chinatiensis n. sp., Novoameura vitrumons n. sp., Anisopyge perannulata (Shumard), and Anisopyge cooperi n. sp.
The lower fauna originated in the late Pennsylvanian, inhabited shallow-water environments, was relatively pandemic, and is interpreted to have become extinct as a result of marine regression during the early to middle Leonardian. The endemic upper fauna originated in deep waters of the Marfa and Delaware Basins during the late Leonardian, and, concurrent with sea level rise, migrated and diversified into the shelf-margin reefs of the late Leonardian and Guadalupian. Regression during the Late Permian resulted in extinction of this second Permian trilobite fauna.