Welcome! Most of this website is devoted to the paleontology of the Hell Creek Formation. To get you in the mood, I have provided these fossil photos for your perusal. The photo (above) is an osteoderm from either the crocodyloid Borealosuchus sternbergi (Gilmore 1910); (formerly called "Leidyosuchus" sternbergi Gilmore) or the alligatoroid Brachychampsa montana Gilmore. Note that the bottom edge of the osteoderm is different from the other edges. This edge faces anterior (toward the snout). I chose the background pattern for this web page because it resembles the cracked surface of the mudstone outcrops of the Hell Creek Formation.
(above) In the palm of this person's hand are fossil turtle and crocodyloid fragments. These fossils are the most common vertebrates found in the Hell Creek Formation. Turtle carapace and plastron fragments (upper right and lower left) are often pebbly in texture. In contrast, some crocodyloid and alligatoroid fragments, usually pieces of the skull (lower right) or osteoderm fragments (like the fossil in the first photo) have large deep pits. Some croc' and 'gator osteoderm fragments are keeled on one side; these are part of the skin armor from the dorsal surface of the animal.
[above] This fossil is a dermal plate from Lepisosteus occidentalis, a gar fish from the Hell Creek Formation. Dermal plates are one of the most common fossils found in the Formation. Gars have many of these rhomb-shaped boney plates in their skin along the sides of their bodies. The plates create a type of flexible armor. This particular plate is 25 mm long (horizontally).
[above] A fossil tooth from the ray Myledaphus bipartitus Cope 1876. Teeth of sharks and rays are sometimes found in the Hell Creek Formation, even though the Formation represents river-layed deposits. Apparently, these taxa were tolerant of fresh water. Height of tooth is 8 mm.
[above] Labial view, lingual view, and a close-up labial view of an Ankylosaurus dentary fragment from the Hell Creek Formation. Collected by little "Flip" Bigelow, age 5, on the ranch of a family friend around 1960. It was "Flip" 's first fossil discovery. His dad had pulled the car over to the side of the road to change a flat tire. "Flip" got out of the car and wandered into a dry wash where he found the bone laying on the surface of the ground. It was not identified as a dinosaur fossil until 1964. Note the leaf-like shape of the teeth, which is characteristic of some plant-eating dinosaurs, but it is particularly characteristic of armored dinosaurs such as Ankylosaurus. Also note that the newer Ankylosaurus teeth are replacing the old, worn teeth on the labial side of the jaw. The total length of the jaw fragment is 40 mm.
(above) Here are two typical Hell Creek Formation theropod teeth. Both are shed teeth. The tooth on the left is from a rather large (but non-tyrannosaurid) theropod. The tooth on the right is from a small tyrannosaur (possibly from a juvenile). Not all tyrannosaur teeth are as large as bananas! Many of the smaller tyrannosaurid teeth are very distinctive because they have unique shapes to their serrations, not to mention possessing a unique feature called "blood grooves". The tooth on the left is 30 mm long, and the ?juvenile tyrannosaur tooth on the right is 31 mm long.
[above] Three views of a claw bone (called an ungual) of a small theropod dinosaur from the Hell Creek Formation, probably of a dromaeosaur or a troodontid. The photo on the far right shows the articular surface (where the bone connects to the adjacent bone). The claw is broken at its tip. Preserved length is 26 mm. Largest dimmension of articular surface (far right photo) is 13 mm.
(above) A thoracic vertebra from a Hell Creek Formation salamander (possibly Scapherpeton tectum Cope 1876). The articular surfaces of the centrum are characteristicly dorsoventrally elongated, with deeply concave (amphicoelous) articular surfaces and numerous lateral pneumapores. The centrum has a
prominent ventral keel. The length of the vertebra is 8.5 mm, and the width of the vertebra, measured between the ends of the transverse processes, is 8.0 mm.
(above) Medial view of a left humerus from the Hell Creek crocodyloid Borealosuchus sternbergi (Gilmore 1910); (formerly called "Leidyosuchus" sternbergi Gilmore). The length of the bone is 89 mm.
