Stratigraphic Distribution of Vertebrate Localities in The Upper Cretaceous (?Santonian-Campanian) Menefee Formation in The Southeastern San Juan Basin
— Andrew B. Heckert, Spencer G. Lucas, Caleb Lewis, Austin Deans, Alex Harrison, and Amanda Hendrix

Upper Cretaceous strata in the San Juan Basin yield abundant nonmarine vertebrate fossils of late Campanian–Maastrichtian
(Judithian, Kirtlandian, Lancian) age from the Fruitland and Kirtland formations. Much less well known are older assemblages from the
Menefee Formation, which is of early Campanian age based on the age of over- and underlying marine units. Here we document an especially
fossiliferous interval stratigraphically high in the Allison Member of the Menefee Formation. The Allison Member yields a nonmarine
assemblage of rays, osteichthyans, turtles, and dinosaurs, but other fossils include marine chondrichthyans and trace fossils of Teredolites,
associated with marine bivalves. This suggests that the upper Allison Member was sufficiently close to the shoreline of the Western Interior
Seaway for the latter to exert influence on its biota. Relatively few Menefee Formation fossils are identifiable to the genus level, but the
herpetofauna, particularly the turtles and dinosaurs, are taxonomically similar to those elements in younger Late Cretaceous vertebrate
faunas across Laramidia.