Organ Rock Formation Organ Rock Formation The Organ Rock Formation or Organ Rock Shale is a formation within the late Pennsylvanian to early Permian Cutler Group and is deposited across southeastern Utah, northwestern New Mexico, and northeastern Arizona. This formation notably outcrops around Canyonlands National Park, Natural Bridges National Monument, and Monument Valley. The age of the Organ Rock is constrained to the latter half of the Cisuralian Epoch by age dates from overlying and underlying formations. Important early terrestrial vertebrate fossils have been recovered from this formation in northern Arizona, southern Utah, and northern New Mexico. These include the iconic Permian terrestrial
Organ Rock Formation seymouriamorph found in the Organ Rock Formation. "Seymouria sanjuanensis" is a unique taxon because of its extensive geographic range. This particular animal was first described by Vaughn (1966) from the Organ Rock Formation. Since this initial find, a number of these individuals have been recovered from localities as distant as Germany. Four early synapsid taxa are present within the Organ Rock Formation. These include Ophiacodon, as well as three sphenacodontids: "Ctenospondylus", "Dimetrodon", and "Sphenacodon ferocior". Most taxa are known from fragmentary material. Early synapsids were dominant members of the terrestrial Permian ecosystem. Some early synapsids adapted an herbivorous diet, however,