• The Arroyo Formaton (Leonardian: Lower Permian) and Its Vertebrate Fossils 

    Olson, Everett C. (Texas Memorial Museum, The University of Texas at Austin, 1989-07)
    Studies of the Arroyo formation from northern Haskell County south to Runnels County, Texas trace the changes in organisms and environments from the classic terrestrial beds of Baylor and Wilbarger Counties to the fully ...