![Nautilus fossil](https://samnoblemuseum.ou.edu/wp-content/uploads/2017/02/Cymatoceras-hilli-OU-39168.jpg)
![Nautilus fossil](https://samnoblemuseum.ou.edu/wp-content/uploads/2017/02/Cymatoceras-hilli-OU-39168-839x1024.jpg)
Cymatoceras hilliOU 39168; Nautiloid; Lower Cretaceous; Grayson Formation; Marshall County, Oklahoma; CC BY-NC-ND 4.0
Cymatoceras hilli
![Ammonite fossil](https://samnoblemuseum.ou.edu/wp-content/uploads/2017/02/Metengonoceras-dumbli-OU-37822.jpg)
![Ammonite fossil](https://samnoblemuseum.ou.edu/wp-content/uploads/2017/02/Metengonoceras-dumbli-OU-37822-851x1024.jpg)
Metengonoceras dumbliOU 37822; Ammonite; Lower Cretaceous; Duck Creek Member, Caddo Formation; Marshall County, Oklahoma; CC BY-NC-ND 4.0
Metengonoceras dumbli
![Ammonite fossil](https://samnoblemuseum.ou.edu/wp-content/uploads/2017/02/Mortonicera-Drakeoceras-maximum-OU37403.jpg)
![Ammonite fossil](https://samnoblemuseum.ou.edu/wp-content/uploads/2017/02/Mortonicera-Drakeoceras-maximum-OU37403-889x1024.jpg)
Mortoniceras (Drakeoceras) maximumOU 37403; Ammonite; Lower Cretaceous; Caddo Formation; Marshall County, Oklahoma; CC BY-NC-ND 4.0
Mortoniceras (Drakeoceras) maximum
![Ammonite fossil](https://samnoblemuseum.ou.edu/wp-content/uploads/2017/02/Mortoniceras-Mortoniceras-smedalae-OU-3436.jpg)
![Ammonite fossil](https://samnoblemuseum.ou.edu/wp-content/uploads/2017/02/Mortoniceras-Mortoniceras-smedalae-OU-3436-873x1024.jpg)
Mortoniceras (Mortoniceras) smedalaeOU 3436; Ammonite; Lower Cretaceous; Duck Creek Member, Caddo Formation; Marshall County, Oklahoma; CC BY-NC-ND 4.0
Mortoniceras (Mortoniceras) smedalae
![Ammonite fossil](https://samnoblemuseum.ou.edu/wp-content/uploads/2017/02/Nortoniceras-Drakeoceras-sp..jpg)
![Ammonite fossil](https://samnoblemuseum.ou.edu/wp-content/uploads/2017/02/Nortoniceras-Drakeoceras-sp.-855x1024.jpg)
Mortoniceras (Drakeoceras) sp.Ammonite; Lower Cretaceous; Weno Formation; Marshall County, Oklahoma; CC BY-NC-ND 4.0
Mortoniceras (Drakeoceras) sp.
![Ammonite fossil](https://samnoblemuseum.ou.edu/wp-content/uploads/2017/02/Scaphites-sp..jpg)
![Ammonite fossil](https://samnoblemuseum.ou.edu/wp-content/uploads/2017/02/Scaphites-sp.-902x1024.jpg)
Scaphites sp.Ammonite; Lower Cretaceous; Duck Creek Member, Caddo Formation; Marshall County, Oklahoma; CC BY-NC-ND 4.0
Scaphites sp.
![Ammonite fossil](https://samnoblemuseum.ou.edu/wp-content/uploads/2017/02/Oxytropidoceras.jpg)
![Ammonite fossil](https://samnoblemuseum.ou.edu/wp-content/uploads/2017/02/Oxytropidoceras-827x1024.jpg)
Oxytropidoceras supaniAmmonite; Lower Cretaceous; Kiamichi Formation; Bryan County, Oklahoma; CC BY-NC-ND 4.0
Oxytropidoceras supani
![Ammonite fossil](https://samnoblemuseum.ou.edu/wp-content/uploads/2017/02/Idiohamites-sp.-OU-3437.jpg)
![Ammonite fossil](https://samnoblemuseum.ou.edu/wp-content/uploads/2017/02/Idiohamites-sp.-OU-3437-814x1024.jpg)
Idiohamites sp.OU 3437; Ammonite; Lower Cretaceous; Duck Creek Member, Caddo Formation; Marshall County, Oklahoma; CC BY-NC-ND 4.0
Idiohamites sp.
![Ammonite fossil](https://samnoblemuseum.ou.edu/wp-content/uploads/2017/02/Hamites-fremonti.jpg)
![Ammonite fossil](https://samnoblemuseum.ou.edu/wp-content/uploads/2017/02/Hamites-fremonti-1024x737.jpg)
Hamites fremontiAmmonite; Lower Cretaceous; Duck Creek Member, Caddo Formation; Marshall County, Oklahoma; CC BY-NC-ND 4.0
Hamites fremonti
![Ammonite fossil](https://samnoblemuseum.ou.edu/wp-content/uploads/2017/02/Turrilites.jpg)
![Ammonite fossil](https://samnoblemuseum.ou.edu/wp-content/uploads/2017/02/Turrilites-503x1024.jpg)
Turrilites acutusAmmonite; Upper Cretaceous; Eagle Ford Formation; Bryan County, Oklahoma; CC BY-NC-ND 4.0