New Mexico Geological Society Annual Spring Meeting — Abstracts

In the San Juan Basin, the uppennost strata of the Pictured Cliff Sandstone record the last traces of the Cretaceous Interior Seaway as it retreated across the continent. A vertebrate fossil locality in the Pictured Cliffs Sandstone at Mesa Portales near Cuba contains much more terrestrial elements than do other marginal marine sandstones lower in the Upper Cretaceous section. This site is dominated by selachians with 15 species: Squalicorax pristodontus, Isehyrhiza mira, Hybodus sp., Syneehodus sp., Squatina sp.,I Pseudohypolophus menultyi, Odontaspis cheethami, Odontaspis sanguinei, Cretodus areuata, Cretolamna appendiculata, Plyehotrygon triangularis, Ptyehotrygon sp. A, Braehaelurus sp., Cretodus borodini, Cretodus sp. and calcified selachian centra. The site also contains teleost centra of at least two different species as well as teleost bone fragments and some very large teeth of Enchodus. There are at least five kinds of reptiles present: turtles, elasmosaurs, alligators, omithischians and saurischians. Also, some very tiny mammal teeth are found at this locality. The selachian fauna contains some members that are age diagnostic, such as Squalicorax pristodontus. While this fauna compares well with other late Campanian selachian faunas there is at least one species that is obviously missing, the teeth of Ptychodus mortoni. This has some paleoecological
implications for the locality and suggests that the water during the time of deposition was very shallow. The presence of dinosaur and mammal teeth also suggests that this site was vcry close to land.