New Mexico's Cretaceous Ammonites
Cretaceous ammonites are abundant and diverse in the state of New Mexico. They mainly occur in the Mancos Shale, Lewis Shale and Dakota Formation in the San Juan Basin, the Pierre Shale and Niobrara in the Raton basin, the Mancos Shale in south-central New Mexico, the Mesa Rica Sandstone and Tucumcari Formation in eastern New Mexico and the Colorado, Mojado and U-Bar formations in southwestern New Mexico.
The history of ammonite collecting in New Mexico
In the 1800’s early explorers like J. S. Newberry and Captain J. N. Macomb discovered fossils, including ammonites, in New Mexico. Later in the 1900’s Herrick and Johnson collected ammonites from the state. In the 1930’s C. B. Hunt collected ammonites from New Mexico. Several eminent invertebrate paleontologists and geologists have collected and published on Late Cretaceous ammonites from New Mexico. They include J. B. Reeside Jr., W. T. Lee, and W. A. Cobban.
The importance of New Mexico ammonites
Many new ammonites from New Mexico have been named new genera or species. Cobban, Hook & Kennedy (1989, p. 38) named a new ammonite called Burroceras clydense from the Big Burro Mountains in Grant County, New Mexico. This ammonite is an upper Cenomanian ammonite zone for the Western Interior of the United States. Other ammonites named by Cobban et al. (1989) from southwestern New Mexico include Cunningtoniceras novimexicanum, C. cookense, Calycoceras inflatum, Neocardioceras woodwardi, Watinoceras odonnelli, Euomphaloceras merewetheri, E. costatum, Burroceras irregulare, B. transitorium, Paraburroceras, P. minutum, Vascoceras barcoicense exile, Infabricaticeras, I. lunaense, Microdiphasoceras, M. novimexicanum, Rubroceras, R. alatum, R. burroense, R. rotundum, Hamites salebrosus, H. pygmaeus, Metaptychoceras hidalgoense, Neostlingoceras procerum, N. bayardense, N. virdenense, and N. apiculatum. Other ammonites named from New Mexico include Neostlingoceras kottlowskii Cobban and Hook, 1981, Spathites puercoensis (Herrick & Johnson, 1900), Tragodesmoceras socorroense Cobban and Hook, 1979, Texanites omeraensis (Reeside), Reginaites leei (Reeside), Cibolaites molenaari Cobban and Hook, 1983, Prionocyclus novimexicanus (Marcou, 1858), Hoplitoides sandovalensis Cobban and Hook, 1980, Coilopoceras colleti Hyatt, 1903, Coilopoceras springeri Hyatt, 1903, Coilopoceras inflatum Cobban and Hook, 1980, Herrickiceras costatum (Herrick and Johnson, 1900), Scaphites leei Reeside, 1927 and Glyptoxoceras novimexicanum (Reeside, 1927).