New Mexico Geological Society Annual Spring Meeting — Abstracts

Few early Campanian terrestrial vertebrate faunas have been described from western North America. Consequently, it is not known if the pattern of high diversity and high provinciality that characterized middle and late Campanian biotas also prevailed in the early Campanian. Here we provide an updated list of a vertebrate assemblage from the Santonian – lower Campanian Menefee Formation from near the southeastern margin of the San Juan Basin, southwest of San Ysidro, New Mexico that we name the Armijo Draw local fauna. This fauna provides new information from a “southern” terrestrial faunal assemblage.

The Armijo Draw local fauna is from a relatively small (< 2 km²) exposure of Menefee badlands that is bounded by normal faults. Unlike most Menefee exposures, this one is relatively rich in well-preserved vertebrate fossils. New vertebrate fossils were recovered from this locale through a combination of surface prospecting and from screenwashing of bulk samples. New macrovertebrate fossils include a partial ceratopsian braincase, bones of a hadrosauroid, and fragmentary postcrania of a theropod. A microvertate assemblage from NMMNH locality L-8849 includes a “typical” Campanian age biota including osteichthyan scales and teeth representing several taxa (e.g., lepisosteid genus et sp. indet, amiid gen. et sp. indet. and Paralbula sp.), teeth representing numerous fresh water chondrichthyan taxa (e.g., Lissodus sp., Hybodus sp., Orectolobidae gen. et sp. undet., cf. Myledaphus sp., Pseudohypolophus sp., Ptychotrygon sp.), teeth of crocodilians, teeth of ornithischian dinosaurs, and tooth fragments of therian mammals. The Armijo Draw local fauna resembles other Campanian age, coastal plain vertebrate assemblages of western North America.