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Cody Field Office



 Natural Trap Cave

 Archaeological Site Looting


A cast of an Allosaurus head.
The cast of the head of "Big Al", the Allosaurus, on display in the Cody
Field Office. (BLM CYFO photo)
The BLM Cody Field Office (CYFO) has many areas rich in scientifically significant paleontological resources (body fossils such as bones and teeth, trace fossils, etc.) which are actively studied by colleges, universities, museums and consultants. Many of the paleontological excavations in the CYFO area take place in Mesozoic-age sandstones sometimes called bone beds. Bone beds often include the remains of several individual dinosaur carcasses, concentrated by river currents at gravel bars or river bends. The Jurassic Morrison Formation produces some of the most famous dinosaur fossils in the United States.

One of the more prominent specimens found on public lands in the CYFO is of a large carnivorous dinosaur or theropod known as Allosaurus fragilis, nicknamed Big Al. Big Al was excavated in 1991 by the University of Wyoming and the Museum of The Rockies. About 95% of the bones were recovered during the excavation. A cast of his skull is on display at the CYFO, and another cast is on loan to the Buffalo Bill Historical Center in Cody. Big Al was a juvenile and his skeleton was not associated with any other dinosaurs. Nineteen of his bones were broken or showed signs of infection which may have contributed to Big Al's death. The actual fossil bones of Big Al are located at the Museum of the Rockies in Bozeman, Montana.

Stegosaurus sp. from the Jurassic Morrison Formation.
Stegosaurus sp. from the Jurassic Morrison Formation (BLM CYFO Photo)
In the bonebed layers or strata below where Big Al was found, several other fossil dinosaur specimens were discovered and excavated for further study at the University of Chicago during the summers of 2010 and 2011. These other dinosaurs include the plant-eating sauropod Camarasaurus and a species of Stegosaurus.

Many different species of Jurassic-age dinosaurs have been unearthed from the Morrison Formation in the CYFO including: Allosaurus, Apatosaurus, Camarasaurus, Diplodocus, and Stegosaurus. Quite often, theropod teeth have been found when exhuming sauropod bones. The Sundance Formation has also yielded fossils of numerous marine reptiles including Ichthyosaurus and Plesiosaurus

Although Jurassic-age fossils are important, younger Cretaceous dinosaurs are also found and excavated in the CYFO. The early Cretaceous Cloverly Formation has recently produced excellent partial specimens of Tenontosaurus, a relatively small ornithopod or "bird-hipped" dinosaur.

Fossil teeth and mandible.
Plant fossils.
Additionally, younger Paleocene, Eocene, and Pleistocene-age strata and deposits within the boundaries of the CYFO produce mammal and plant fossils of international significance. The photos to the right illustrate mammalian fossils (teeth and mandible) from the Eocene Willwood Formation (from the U.S. Geological Survey) and plant fossils from the same formation below (Wing et al., 2005).

Recent research in the CYFO portion of the Bighorn Basin has centered around fossiliferous freshwater limestones in the Eocene Willwood and Paleocene Fort Union formations, and on an internationally known and scientifically-significant geologic contact situated between the Paleocene and Eocene epochs about 56 million years ago, known as the Paleocene Eocene Thermal Maximum or PETM. This stratigraphic zone in the Bighorn Basin produces important geochemical and paleontological data used by geoscientists to study mammalian evolution, worldwide extinctions and paleoclimate scenarios. Continental PETM sites are rare, and the Bighorn Basin is one of the best PETM localities in the world.

Survey & Excavation Permits

Paleontological Resource Use Permits authorize collection of scientifically significant fossils from BLM public land by qualified scientists, researchers and consultants. Institutions currently holding excavation permits in the CYFOinclude the Smithsonian Institution, Project Exploration and the University of Chicago, the Virginia Museum of Natural History, the University of Michigan, and Casper College/Tate Museum, among others. The BLM Wyoming State Office also issues permits to qualified paleontological consultants working on projects on federal lands. Scientifically significant fossils are defined as all vertebrate fossils and their tracks or traces, and some invertebrate or plant fossils identified as rare or important by the scientific community. Scientifically significant fossils may not be collected by anyone except holders of a BLM-approved permit authorizing such collection. Two types of permits may be issued by the BLM to qualified paleontologists or paleontological consultants:

  1. Exploration Permits, also known as survey permits, which allow the qualified permit holder to search for evidence of vertebrate or other scientifically significant fossils and remove surface fossils as long as the surface disturbance is less than one square meter. An exploration/survey permit is also issued to qualified paleontological consultants for the purpose of investigating commercial ventures such as pipelines, coal mines, oil and gas pads, powerlines, roads or any major disturbing activity that may occur in areas that are suspected to have significant paleontological values.
  2. Excavation Permits allow the permittee to excavate paleontological resources from the earth and to further explore for buried fossils as needed at a paleontological locality or localities. Such activities may also facilitate removal of the fossils for research purposes and to allow scientific mapping, research on taphonomy (the study of how organisms became fossilized), photography and other research-related activities. Before authorizing an excavation permit, the CYFO needs to assess potential impacts to the area, including a site review by the BLM archeologist and wildlife biologist. As required by the National Environmental Policy Act, an environmental assessment must be written to document any and all concerns related to the proposed excavation, which must then be approved by the field manager of the CYFO (the authorized officer).

Collection of Common Invertebrate and Plant Fossils

Visitors to BLM public lands can enjoy and collect reasonable amounts of common invertebrate fossils, such as clams, snails, cephalopods/ammonites, trilobites, and common plant fossils, such as leaf impressions, without a BLM permit. Petrified wood can be collected for personal use only (not for commercial resale) — up to 25 pounds each day, plus one piece, but no more than 250 pounds in any calendar year (43 CFR 3622). These materials must be for your personal collection and cannot be sold or bartered to commercial dealers. There are other laws regarding collection of petrified wood and some lands may be closed to hobby or casual collecting of fossils, so it’s a good idea to check in with the CYFO prior to collecting. On private lands, fossils may only be collected with the permission of the landowner.

Gryphaea sp. “Devil’s toenails”.
Gryphaea sp. “Devil’s toenails”
Ammonite (cephalopod).
Ammonite (cephalopod)

For more information about the fascinating paleontology in Wyoming’s Bighorn Basin, please visit the following websites:

For more information about paleontology on BLM public lands, including information about education, permitting and collecting fossils, and about the new Paleontological Resources Protection Act (2009), please visit this website: