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The age of the vertebrates from the Rattlesnake Canyon locality in western Archer County is currently considered to be latest Wolfcampian-earliest Leonardian or latest Gearyan (latest Pennsylvanian). Comparison of the shark teeth obtained by bulk-sediment sampling with those obtained in a similar manner from younger Loenardian localities in the same region and from Pennsylvanian (Virgilian) localities in Nebraska and the Dunkard basin favors a Permian age, but with reservations due partly to the coexistence of taxa with freshwater and marine affinities.

Three species of xenacanthodiids occur here (two are rare) and in younger deposits; they are unknown from the older deposits. A new species occurs in Nebraska. Six new species of hybodontoids occur in the Texas deposits, but only two occur at Rattlesnake Canyon (one exclusively); at least five of them occur in Nebraska, but all remain unknown from the Dunkard basin. One species (new) of helodontid occurs in the Texas localities; it is rare at Rattlesnake Canyon, known only from the Wolfcampian in the Dunkard basin, but many occur in the Nebraskan Virgilian. Iniopterygians have previously been reported only from the Pennsylvanian, including the Nebraska locality, but not from the Dunkard basin; a new genus occurs at Rattlesnake Canyon, but the group is absent from younger deposits. Cte acanthoids and petalodontiids are too rare and poorly understood taxonomically to permit a significant analysis.

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